FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_bus.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 1997,1998,2003 Doug Rabson
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_bus.h"
    #include "opt_ddb.h"
    
    #include <sys/param.h>
    #include <sys/conf.h>
    #include <sys/domainset.h>
    #include <sys/eventhandler.h>
    #include <sys/lock.h>
    #include <sys/kernel.h>
    #include <sys/limits.h>
    #include <sys/malloc.h>
    #include <sys/module.h>
    #include <sys/mutex.h>
    #include <sys/priv.h>
    #include <machine/bus.h>
    #include <sys/random.h>
    #include <sys/refcount.h>
    #include <sys/rman.h>
    #include <sys/sbuf.h>
    #include <sys/smp.h>
    #include <sys/sysctl.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    #include <sys/cpuset.h>
    
    #include <net/vnet.h>
    
    #include <machine/cpu.h>
    #include <machine/stdarg.h>
    
    #include <vm/uma.h>
    #include <vm/vm.h>
    
    #include <ddb/ddb.h>
    
    SYSCTL_NODE(_hw, OID_AUTO, bus, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
        NULL);
    SYSCTL_ROOT_NODE(OID_AUTO, dev, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
        NULL);
    
    static bool disable_failed_devs = false;
    SYSCTL_BOOL(_hw_bus, OID_AUTO, disable_failed_devices, CTLFLAG_RWTUN, &disable_failed_devs,
        0, "Do not retry attaching devices that return an error from DEVICE_ATTACH the first time");
    
    /*
     * Used to attach drivers to devclasses.
     */
    typedef struct driverlink *driverlink_t;
    struct driverlink {
            kobj_class_t    driver;
            TAILQ_ENTRY(driverlink) link;   /* list of drivers in devclass */
            int             pass;
            int             flags;
    #define DL_DEFERRED_PROBE       1       /* Probe deferred on this */
            TAILQ_ENTRY(driverlink) passlink;
    };
    
    /*
     * Forward declarations
     */
    typedef TAILQ_HEAD(devclass_list, devclass) devclass_list_t;
    typedef TAILQ_HEAD(driver_list, driverlink) driver_list_t;
    typedef TAILQ_HEAD(device_list, _device) device_list_t;
    
    struct devclass {
            TAILQ_ENTRY(devclass) link;
            devclass_t      parent;         /* parent in devclass hierarchy */
            driver_list_t   drivers;        /* bus devclasses store drivers for bus */
           char            *name;
           device_t        *devices;       /* array of devices indexed by unit */
           int             maxunit;        /* size of devices array */
           int             flags;
   #define DC_HAS_CHILDREN         1
   
           struct sysctl_ctx_list sysctl_ctx;
           struct sysctl_oid *sysctl_tree;
   };
   
   /**
    * @brief Implementation of _device.
    *
    * The structure is named "_device" instead of "device" to avoid type confusion
    * caused by other subsystems defining a (struct device).
    */
   struct _device {
           /*
            * A device is a kernel object. The first field must be the
            * current ops table for the object.
            */
           KOBJ_FIELDS;
   
           /*
            * Device hierarchy.
            */
           TAILQ_ENTRY(_device)    link;   /**< list of devices in parent */
           TAILQ_ENTRY(_device)    devlink; /**< global device list membership */
           device_t        parent;         /**< parent of this device  */
           device_list_t   children;       /**< list of child devices */
   
           /*
            * Details of this device.
            */
           driver_t        *driver;        /**< current driver */
           devclass_t      devclass;       /**< current device class */
           int             unit;           /**< current unit number */
           char*           nameunit;       /**< name+unit e.g. foodev0 */
           char*           desc;           /**< driver specific description */
           u_int           busy;           /**< count of calls to device_busy() */
           device_state_t  state;          /**< current device state  */
           uint32_t        devflags;       /**< api level flags for device_get_flags() */
           u_int           flags;          /**< internal device flags  */
           u_int   order;                  /**< order from device_add_child_ordered() */
           void    *ivars;                 /**< instance variables  */
           void    *softc;                 /**< current driver's variables  */
   
           struct sysctl_ctx_list sysctl_ctx; /**< state for sysctl variables  */
           struct sysctl_oid *sysctl_tree; /**< state for sysctl variables */
   };
   
   static MALLOC_DEFINE(M_BUS, "bus", "Bus data structures");
   static MALLOC_DEFINE(M_BUS_SC, "bus-sc", "Bus data structures, softc");
   
   EVENTHANDLER_LIST_DEFINE(device_attach);
   EVENTHANDLER_LIST_DEFINE(device_detach);
   EVENTHANDLER_LIST_DEFINE(device_nomatch);
   EVENTHANDLER_LIST_DEFINE(dev_lookup);
   
   static void devctl2_init(void);
   static bool device_frozen;
   
   #define DRIVERNAME(d)   ((d)? d->name : "no driver")
   #define DEVCLANAME(d)   ((d)? d->name : "no devclass")
   
   #ifdef BUS_DEBUG
   
   static int bus_debug = 1;
   SYSCTL_INT(_debug, OID_AUTO, bus_debug, CTLFLAG_RWTUN, &bus_debug, 0,
       "Bus debug level");
   #define PDEBUG(a)       if (bus_debug) {printf("%s:%d: ", __func__, __LINE__), printf a; printf("\n");}
   #define DEVICENAME(d)   ((d)? device_get_name(d): "no device")
   
   /**
    * Produce the indenting, indent*2 spaces plus a '.' ahead of that to
    * prevent syslog from deleting initial spaces
    */
   #define indentprintf(p) do { int iJ; printf("."); for (iJ=0; iJ<indent; iJ++) printf("  "); printf p ; } while (0)
   
   static void print_device_short(device_t dev, int indent);
   static void print_device(device_t dev, int indent);
   void print_device_tree_short(device_t dev, int indent);
   void print_device_tree(device_t dev, int indent);
   static void print_driver_short(driver_t *driver, int indent);
   static void print_driver(driver_t *driver, int indent);
   static void print_driver_list(driver_list_t drivers, int indent);
   static void print_devclass_short(devclass_t dc, int indent);
   static void print_devclass(devclass_t dc, int indent);
   void print_devclass_list_short(void);
   void print_devclass_list(void);
   
   #else
   /* Make the compiler ignore the function calls */
   #define PDEBUG(a)                       /* nop */
   #define DEVICENAME(d)                   /* nop */
   
   #define print_device_short(d,i)         /* nop */
   #define print_device(d,i)               /* nop */
   #define print_device_tree_short(d,i)    /* nop */
   #define print_device_tree(d,i)          /* nop */
   #define print_driver_short(d,i)         /* nop */
   #define print_driver(d,i)               /* nop */
   #define print_driver_list(d,i)          /* nop */
   #define print_devclass_short(d,i)       /* nop */
   #define print_devclass(d,i)             /* nop */
   #define print_devclass_list_short()     /* nop */
   #define print_devclass_list()           /* nop */
   #endif
   
   /*
    * dev sysctl tree
    */
   
   enum {
           DEVCLASS_SYSCTL_PARENT,
   };
   
   static int
   devclass_sysctl_handler(SYSCTL_HANDLER_ARGS)
   {
           devclass_t dc = (devclass_t)arg1;
           const char *value;
   
           switch (arg2) {
           case DEVCLASS_SYSCTL_PARENT:
                   value = dc->parent ? dc->parent->name : "";
                   break;
           default:
                   return (EINVAL);
           }
           return (SYSCTL_OUT_STR(req, value));
   }
   
   static void
   devclass_sysctl_init(devclass_t dc)
   {
           if (dc->sysctl_tree != NULL)
                   return;
           sysctl_ctx_init(&dc->sysctl_ctx);
           dc->sysctl_tree = SYSCTL_ADD_NODE(&dc->sysctl_ctx,
               SYSCTL_STATIC_CHILDREN(_dev), OID_AUTO, dc->name,
               CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
           SYSCTL_ADD_PROC(&dc->sysctl_ctx, SYSCTL_CHILDREN(dc->sysctl_tree),
               OID_AUTO, "%parent",
               CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
               dc, DEVCLASS_SYSCTL_PARENT, devclass_sysctl_handler, "A",
               "parent class");
   }
   
   enum {
           DEVICE_SYSCTL_DESC,
           DEVICE_SYSCTL_DRIVER,
           DEVICE_SYSCTL_LOCATION,
           DEVICE_SYSCTL_PNPINFO,
           DEVICE_SYSCTL_PARENT,
   };
   
   static int
   device_sysctl_handler(SYSCTL_HANDLER_ARGS)
   {
           struct sbuf sb;
           device_t dev = (device_t)arg1;
           int error;
   
           sbuf_new_for_sysctl(&sb, NULL, 1024, req);
           sbuf_clear_flags(&sb, SBUF_INCLUDENUL);
           bus_topo_lock();
           switch (arg2) {
           case DEVICE_SYSCTL_DESC:
                   sbuf_cat(&sb, dev->desc ? dev->desc : "");
                   break;
           case DEVICE_SYSCTL_DRIVER:
                   sbuf_cat(&sb, dev->driver ? dev->driver->name : "");
                   break;
           case DEVICE_SYSCTL_LOCATION:
                   bus_child_location(dev, &sb);
                   break;
           case DEVICE_SYSCTL_PNPINFO:
                   bus_child_pnpinfo(dev, &sb);
                   break;
           case DEVICE_SYSCTL_PARENT:
                   sbuf_cat(&sb, dev->parent ? dev->parent->nameunit : "");
                   break;
           default:
                   error = EINVAL;
                   goto out;
           }
           error = sbuf_finish(&sb);
   out:
           bus_topo_unlock();
           sbuf_delete(&sb);
           return (error);
   }
   
   static void
   device_sysctl_init(device_t dev)
   {
           devclass_t dc = dev->devclass;
           int domain;
   
           if (dev->sysctl_tree != NULL)
                   return;
           devclass_sysctl_init(dc);
           sysctl_ctx_init(&dev->sysctl_ctx);
           dev->sysctl_tree = SYSCTL_ADD_NODE_WITH_LABEL(&dev->sysctl_ctx,
               SYSCTL_CHILDREN(dc->sysctl_tree), OID_AUTO,
               dev->nameunit + strlen(dc->name),
               CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "", "device_index");
           SYSCTL_ADD_PROC(&dev->sysctl_ctx, SYSCTL_CHILDREN(dev->sysctl_tree),
               OID_AUTO, "%desc", CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
               dev, DEVICE_SYSCTL_DESC, device_sysctl_handler, "A",
               "device description");
           SYSCTL_ADD_PROC(&dev->sysctl_ctx, SYSCTL_CHILDREN(dev->sysctl_tree),
               OID_AUTO, "%driver",
               CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
               dev, DEVICE_SYSCTL_DRIVER, device_sysctl_handler, "A",
               "device driver name");
           SYSCTL_ADD_PROC(&dev->sysctl_ctx, SYSCTL_CHILDREN(dev->sysctl_tree),
               OID_AUTO, "%location",
               CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
               dev, DEVICE_SYSCTL_LOCATION, device_sysctl_handler, "A",
               "device location relative to parent");
           SYSCTL_ADD_PROC(&dev->sysctl_ctx, SYSCTL_CHILDREN(dev->sysctl_tree),
               OID_AUTO, "%pnpinfo",
               CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
               dev, DEVICE_SYSCTL_PNPINFO, device_sysctl_handler, "A",
               "device identification");
           SYSCTL_ADD_PROC(&dev->sysctl_ctx, SYSCTL_CHILDREN(dev->sysctl_tree),
               OID_AUTO, "%parent",
               CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
               dev, DEVICE_SYSCTL_PARENT, device_sysctl_handler, "A",
               "parent device");
           if (bus_get_domain(dev, &domain) == 0)
                   SYSCTL_ADD_INT(&dev->sysctl_ctx,
                       SYSCTL_CHILDREN(dev->sysctl_tree), OID_AUTO, "%domain",
                       CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, domain, "NUMA domain");
   }
   
   static void
   device_sysctl_update(device_t dev)
   {
           devclass_t dc = dev->devclass;
   
           if (dev->sysctl_tree == NULL)
                   return;
           sysctl_rename_oid(dev->sysctl_tree, dev->nameunit + strlen(dc->name));
   }
   
   static void
   device_sysctl_fini(device_t dev)
   {
           if (dev->sysctl_tree == NULL)
                   return;
           sysctl_ctx_free(&dev->sysctl_ctx);
           dev->sysctl_tree = NULL;
   }
   
   static struct device_list bus_data_devices;
   static int bus_data_generation = 1;
   
   static kobj_method_t null_methods[] = {
           KOBJMETHOD_END
   };
   
   DEFINE_CLASS(null, null_methods, 0);
   
   void
   bus_topo_assert(void)
   {
   
           GIANT_REQUIRED; 
   }
   
   struct mtx *
   bus_topo_mtx(void)
   {
   
           return (&Giant);
   }
   
   void
   bus_topo_lock(void)
   {
   
           mtx_lock(bus_topo_mtx());
   }
   
   void
   bus_topo_unlock(void)
   {
   
           mtx_unlock(bus_topo_mtx());
   }
   
   /*
    * Bus pass implementation
    */
   
   static driver_list_t passes = TAILQ_HEAD_INITIALIZER(passes);
   int bus_current_pass = BUS_PASS_ROOT;
   
   /**
    * @internal
    * @brief Register the pass level of a new driver attachment
    *
    * Register a new driver attachment's pass level.  If no driver
    * attachment with the same pass level has been added, then @p new
    * will be added to the global passes list.
    *
    * @param new           the new driver attachment
    */
   static void
   driver_register_pass(struct driverlink *new)
   {
           struct driverlink *dl;
   
           /* We only consider pass numbers during boot. */
           if (bus_current_pass == BUS_PASS_DEFAULT)
                   return;
   
           /*
            * Walk the passes list.  If we already know about this pass
            * then there is nothing to do.  If we don't, then insert this
            * driver link into the list.
            */
           TAILQ_FOREACH(dl, &passes, passlink) {
                   if (dl->pass < new->pass)
                           continue;
                   if (dl->pass == new->pass)
                           return;
                   TAILQ_INSERT_BEFORE(dl, new, passlink);
                   return;
           }
           TAILQ_INSERT_TAIL(&passes, new, passlink);
   }
   
   /**
    * @brief Raise the current bus pass
    *
    * Raise the current bus pass level to @p pass.  Call the BUS_NEW_PASS()
    * method on the root bus to kick off a new device tree scan for each
    * new pass level that has at least one driver.
    */
   void
   bus_set_pass(int pass)
   {
           struct driverlink *dl;
   
           if (bus_current_pass > pass)
                   panic("Attempt to lower bus pass level");
   
           TAILQ_FOREACH(dl, &passes, passlink) {
                   /* Skip pass values below the current pass level. */
                   if (dl->pass <= bus_current_pass)
                           continue;
   
                   /*
                    * Bail once we hit a driver with a pass level that is
                    * too high.
                    */
                   if (dl->pass > pass)
                           break;
   
                   /*
                    * Raise the pass level to the next level and rescan
                    * the tree.
                    */
                   bus_current_pass = dl->pass;
                   BUS_NEW_PASS(root_bus);
           }
   
           /*
            * If there isn't a driver registered for the requested pass,
            * then bus_current_pass might still be less than 'pass'.  Set
            * it to 'pass' in that case.
            */
           if (bus_current_pass < pass)
                   bus_current_pass = pass;
           KASSERT(bus_current_pass == pass, ("Failed to update bus pass level"));
   }
   
   /*
    * Devclass implementation
    */
   
   static devclass_list_t devclasses = TAILQ_HEAD_INITIALIZER(devclasses);
   
   /**
    * @internal
    * @brief Find or create a device class
    *
    * If a device class with the name @p classname exists, return it,
    * otherwise if @p create is non-zero create and return a new device
    * class.
    *
    * If @p parentname is non-NULL, the parent of the devclass is set to
    * the devclass of that name.
    *
    * @param classname     the devclass name to find or create
    * @param parentname    the parent devclass name or @c NULL
    * @param create        non-zero to create a devclass
    */
   static devclass_t
   devclass_find_internal(const char *classname, const char *parentname,
                          int create)
   {
           devclass_t dc;
   
           PDEBUG(("looking for %s", classname));
           if (!classname)
                   return (NULL);
   
           TAILQ_FOREACH(dc, &devclasses, link) {
                   if (!strcmp(dc->name, classname))
                           break;
           }
   
           if (create && !dc) {
                   PDEBUG(("creating %s", classname));
                   dc = malloc(sizeof(struct devclass) + strlen(classname) + 1,
                       M_BUS, M_NOWAIT | M_ZERO);
                   if (!dc)
                           return (NULL);
                   dc->parent = NULL;
                   dc->name = (char*) (dc + 1);
                   strcpy(dc->name, classname);
                   TAILQ_INIT(&dc->drivers);
                   TAILQ_INSERT_TAIL(&devclasses, dc, link);
   
                   bus_data_generation_update();
           }
   
           /*
            * If a parent class is specified, then set that as our parent so
            * that this devclass will support drivers for the parent class as
            * well.  If the parent class has the same name don't do this though
            * as it creates a cycle that can trigger an infinite loop in
            * device_probe_child() if a device exists for which there is no
            * suitable driver.
            */
           if (parentname && dc && !dc->parent &&
               strcmp(classname, parentname) != 0) {
                   dc->parent = devclass_find_internal(parentname, NULL, TRUE);
                   dc->parent->flags |= DC_HAS_CHILDREN;
           }
   
           return (dc);
   }
   
   /**
    * @brief Create a device class
    *
    * If a device class with the name @p classname exists, return it,
    * otherwise create and return a new device class.
    *
    * @param classname     the devclass name to find or create
    */
   devclass_t
   devclass_create(const char *classname)
   {
           return (devclass_find_internal(classname, NULL, TRUE));
   }
   
   /**
    * @brief Find a device class
    *
    * If a device class with the name @p classname exists, return it,
    * otherwise return @c NULL.
    *
    * @param classname     the devclass name to find
    */
   devclass_t
   devclass_find(const char *classname)
   {
           return (devclass_find_internal(classname, NULL, FALSE));
   }
   
   /**
    * @brief Register that a device driver has been added to a devclass
    *
    * Register that a device driver has been added to a devclass.  This
    * is called by devclass_add_driver to accomplish the recursive
    * notification of all the children classes of dc, as well as dc.
    * Each layer will have BUS_DRIVER_ADDED() called for all instances of
    * the devclass.
    *
    * We do a full search here of the devclass list at each iteration
    * level to save storing children-lists in the devclass structure.  If
    * we ever move beyond a few dozen devices doing this, we may need to
    * reevaluate...
    *
    * @param dc            the devclass to edit
    * @param driver        the driver that was just added
    */
   static void
   devclass_driver_added(devclass_t dc, driver_t *driver)
   {
           devclass_t parent;
           int i;
   
           /*
            * Call BUS_DRIVER_ADDED for any existing buses in this class.
            */
           for (i = 0; i < dc->maxunit; i++)
                   if (dc->devices[i] && device_is_attached(dc->devices[i]))
                           BUS_DRIVER_ADDED(dc->devices[i], driver);
   
           /*
            * Walk through the children classes.  Since we only keep a
            * single parent pointer around, we walk the entire list of
            * devclasses looking for children.  We set the
            * DC_HAS_CHILDREN flag when a child devclass is created on
            * the parent, so we only walk the list for those devclasses
            * that have children.
            */
           if (!(dc->flags & DC_HAS_CHILDREN))
                   return;
           parent = dc;
           TAILQ_FOREACH(dc, &devclasses, link) {
                   if (dc->parent == parent)
                           devclass_driver_added(dc, driver);
           }
   }
   
   static void
   device_handle_nomatch(device_t dev)
   {
           BUS_PROBE_NOMATCH(dev->parent, dev);
           EVENTHANDLER_DIRECT_INVOKE(device_nomatch, dev);
           dev->flags |= DF_DONENOMATCH;
   }
   
   /**
    * @brief Add a device driver to a device class
    *
    * Add a device driver to a devclass. This is normally called
    * automatically by DRIVER_MODULE(). The BUS_DRIVER_ADDED() method of
    * all devices in the devclass will be called to allow them to attempt
    * to re-probe any unmatched children.
    *
    * @param dc            the devclass to edit
    * @param driver        the driver to register
    */
   int
   devclass_add_driver(devclass_t dc, driver_t *driver, int pass, devclass_t *dcp)
   {
           driverlink_t dl;
           devclass_t child_dc;
           const char *parentname;
   
           PDEBUG(("%s", DRIVERNAME(driver)));
   
           /* Don't allow invalid pass values. */
           if (pass <= BUS_PASS_ROOT)
                   return (EINVAL);
   
           dl = malloc(sizeof *dl, M_BUS, M_NOWAIT|M_ZERO);
           if (!dl)
                   return (ENOMEM);
   
           /*
            * Compile the driver's methods. Also increase the reference count
            * so that the class doesn't get freed when the last instance
            * goes. This means we can safely use static methods and avoids a
            * double-free in devclass_delete_driver.
            */
           kobj_class_compile((kobj_class_t) driver);
   
           /*
            * If the driver has any base classes, make the
            * devclass inherit from the devclass of the driver's
            * first base class. This will allow the system to
            * search for drivers in both devclasses for children
            * of a device using this driver.
            */
           if (driver->baseclasses)
                   parentname = driver->baseclasses[0]->name;
           else
                   parentname = NULL;
           child_dc = devclass_find_internal(driver->name, parentname, TRUE);
           if (dcp != NULL)
                   *dcp = child_dc;
   
           dl->driver = driver;
           TAILQ_INSERT_TAIL(&dc->drivers, dl, link);
           driver->refs++;         /* XXX: kobj_mtx */
           dl->pass = pass;
           driver_register_pass(dl);
   
           if (device_frozen) {
                   dl->flags |= DL_DEFERRED_PROBE;
           } else {
                   devclass_driver_added(dc, driver);
           }
           bus_data_generation_update();
           return (0);
   }
   
   /**
    * @brief Register that a device driver has been deleted from a devclass
    *
    * Register that a device driver has been removed from a devclass.
    * This is called by devclass_delete_driver to accomplish the
    * recursive notification of all the children classes of busclass, as
    * well as busclass.  Each layer will attempt to detach the driver
    * from any devices that are children of the bus's devclass.  The function
    * will return an error if a device fails to detach.
    *
    * We do a full search here of the devclass list at each iteration
    * level to save storing children-lists in the devclass structure.  If
    * we ever move beyond a few dozen devices doing this, we may need to
    * reevaluate...
    *
    * @param busclass      the devclass of the parent bus
    * @param dc            the devclass of the driver being deleted
    * @param driver        the driver being deleted
    */
   static int
   devclass_driver_deleted(devclass_t busclass, devclass_t dc, driver_t *driver)
   {
           devclass_t parent;
           device_t dev;
           int error, i;
   
           /*
            * Disassociate from any devices.  We iterate through all the
            * devices in the devclass of the driver and detach any which are
            * using the driver and which have a parent in the devclass which
            * we are deleting from.
            *
            * Note that since a driver can be in multiple devclasses, we
            * should not detach devices which are not children of devices in
            * the affected devclass.
            *
            * If we're frozen, we don't generate NOMATCH events. Mark to
            * generate later.
            */
           for (i = 0; i < dc->maxunit; i++) {
                   if (dc->devices[i]) {
                           dev = dc->devices[i];
                           if (dev->driver == driver && dev->parent &&
                               dev->parent->devclass == busclass) {
                                   if ((error = device_detach(dev)) != 0)
                                           return (error);
                                   if (device_frozen) {
                                           dev->flags &= ~DF_DONENOMATCH;
                                           dev->flags |= DF_NEEDNOMATCH;
                                   } else {
                                           device_handle_nomatch(dev);
                                   }
                           }
                   }
           }
   
           /*
            * Walk through the children classes.  Since we only keep a
            * single parent pointer around, we walk the entire list of
            * devclasses looking for children.  We set the
            * DC_HAS_CHILDREN flag when a child devclass is created on
            * the parent, so we only walk the list for those devclasses
            * that have children.
            */
           if (!(busclass->flags & DC_HAS_CHILDREN))
                   return (0);
           parent = busclass;
           TAILQ_FOREACH(busclass, &devclasses, link) {
                   if (busclass->parent == parent) {
                           error = devclass_driver_deleted(busclass, dc, driver);
                           if (error)
                                   return (error);
                   }
           }
           return (0);
   }
   
   /**
    * @brief Delete a device driver from a device class
    *
    * Delete a device driver from a devclass. This is normally called
    * automatically by DRIVER_MODULE().
    *
    * If the driver is currently attached to any devices,
    * devclass_delete_driver() will first attempt to detach from each
    * device. If one of the detach calls fails, the driver will not be
    * deleted.
    *
    * @param dc            the devclass to edit
    * @param driver        the driver to unregister
    */
   int
   devclass_delete_driver(devclass_t busclass, driver_t *driver)
   {
           devclass_t dc = devclass_find(driver->name);
           driverlink_t dl;
           int error;
   
           PDEBUG(("%s from devclass %s", driver->name, DEVCLANAME(busclass)));
   
           if (!dc)
                   return (0);
   
           /*
            * Find the link structure in the bus' list of drivers.
            */
           TAILQ_FOREACH(dl, &busclass->drivers, link) {
                   if (dl->driver == driver)
                           break;
           }
   
           if (!dl) {
                   PDEBUG(("%s not found in %s list", driver->name,
                       busclass->name));
                   return (ENOENT);
           }
   
           error = devclass_driver_deleted(busclass, dc, driver);
           if (error != 0)
                   return (error);
   
           TAILQ_REMOVE(&busclass->drivers, dl, link);
           free(dl, M_BUS);
   
           /* XXX: kobj_mtx */
           driver->refs--;
           if (driver->refs == 0)
                   kobj_class_free((kobj_class_t) driver);
   
           bus_data_generation_update();
           return (0);
   }
   
   /**
    * @brief Quiesces a set of device drivers from a device class
    *
    * Quiesce a device driver from a devclass. This is normally called
    * automatically by DRIVER_MODULE().
    *
    * If the driver is currently attached to any devices,
    * devclass_quiesece_driver() will first attempt to quiesce each
    * device.
    *
    * @param dc            the devclass to edit
    * @param driver        the driver to unregister
    */
   static int
   devclass_quiesce_driver(devclass_t busclass, driver_t *driver)
   {
           devclass_t dc = devclass_find(driver->name);
           driverlink_t dl;
           device_t dev;
           int i;
           int error;
   
           PDEBUG(("%s from devclass %s", driver->name, DEVCLANAME(busclass)));
   
           if (!dc)
                   return (0);
   
           /*
            * Find the link structure in the bus' list of drivers.
            */
           TAILQ_FOREACH(dl, &busclass->drivers, link) {
                   if (dl->driver == driver)
                           break;
           }
   
           if (!dl) {
                   PDEBUG(("%s not found in %s list", driver->name,
                       busclass->name));
                   return (ENOENT);
           }
   
           /*
            * Quiesce all devices.  We iterate through all the devices in
            * the devclass of the driver and quiesce any which are using
            * the driver and which have a parent in the devclass which we
            * are quiescing.
            *
            * Note that since a driver can be in multiple devclasses, we
            * should not quiesce devices which are not children of
            * devices in the affected devclass.
            */
           for (i = 0; i < dc->maxunit; i++) {
                   if (dc->devices[i]) {
                           dev = dc->devices[i];
                           if (dev->driver == driver && dev->parent &&
                               dev->parent->devclass == busclass) {
                                   if ((error = device_quiesce(dev)) != 0)
                                           return (error);
                           }
                   }
           }
   
           return (0);
   }
   
   /**
    * @internal
    */
   static driverlink_t
   devclass_find_driver_internal(devclass_t dc, const char *classname)
   {
           driverlink_t dl;
   
           PDEBUG(("%s in devclass %s", classname, DEVCLANAME(dc)));
   
           TAILQ_FOREACH(dl, &dc->drivers, link) {
                   if (!strcmp(dl->driver->name, classname))
                           return (dl);
           }
   
           PDEBUG(("not found"));
           return (NULL);
   }
   
   /**
    * @brief Return the name of the devclass
    */
   const char *
   devclass_get_name(devclass_t dc)
   {
           return (dc->name);
   }
   
   /**
    * @brief Find a device given a unit number
    *
    * @param dc            the devclass to search
    * @param unit          the unit number to search for
    *
    * @returns             the device with the given unit number or @c
    *                      NULL if there is no such device
    */
   device_t
   devclass_get_device(devclass_t dc, int unit)
   {
           if (dc == NULL || unit < 0 || unit >= dc->maxunit)
                   return (NULL);
           return (dc->devices[unit]);
   }
   
   /**
    * @brief Find the softc field of a device given a unit number
    *
    * @param dc            the devclass to search
    * @param unit          the unit number to search for
    *
    * @returns             the softc field of the device with the given
    *                      unit number or @c NULL if there is no such
    *                      device
    */
   void *
   devclass_get_softc(devclass_t dc, int unit)
   {
           device_t dev;
   
           dev = devclass_get_device(dc, unit);
           if (!dev)
                   return (NULL);
   
           return (device_get_softc(dev));
   }
   
   /**
    * @brief Get a list of devices in the devclass
    *
    * An array containing a list of all the devices in the given devclass
    * is allocated and returned in @p *devlistp. The number of devices
    * in the array is returned in @p *devcountp. The caller should free
    * the array using @c free(p, M_TEMP), even if @p *devcountp is 0.
    *
    * @param dc            the devclass to examine
    * @param devlistp      points at location for array pointer return
    *                      value
    * @param devcountp     points at location for array size return value
    *
    * @retval 0            success
    * @retval ENOMEM       the array allocation failed
    */
   int
   devclass_get_devices(devclass_t dc, device_t **devlistp, int *devcountp)
   {
           int count, i;
           device_t *list;
   
           count = devclass_get_count(dc);
           list = malloc(count * sizeof(device_t), M_TEMP, M_NOWAIT|M_ZERO);
           if (!list)
                   return (ENOMEM);
   
           count = 0;
           for (i = 0; i < dc->maxunit; i++) {
                   if (dc->devices[i]) {
                           list[count] = dc->devices[i];
                           count++;
                   }
           }
   
           *devlistp = list;
           *devcountp = count;
  
          return (0);
  }
  
  /**
   * @brief Get a list of drivers in the devclass
   *
   * An array containing a list of pointers to all the drivers in the
   * given devclass is allocated and returned in @p *listp.  The number
   * of drivers in the array is returned in @p *countp. The caller should
   * free the array using @c free(p, M_TEMP).
   *
   * @param dc            the devclass to examine
   * @param listp         gives location for array pointer return value
   * @param countp        gives location for number of array elements
   *                      return value
   *
   * @retval 0            success
   * @retval ENOMEM       the array allocation failed
   */
  int
  devclass_get_drivers(devclass_t dc, driver_t ***listp, int *countp)
  {
          driverlink_t dl;
          driver_t **list;
          int count;
  
          count = 0;
          TAILQ_FOREACH(dl, &dc->drivers, link)
                  count++;
          list = malloc(count * sizeof(driver_t *), M_TEMP, M_NOWAIT);
          if (list == NULL)
                  return (ENOMEM);
  
          count = 0;
          TAILQ_FOREACH(dl, &dc->drivers, link) {
                  list[count] = dl->driver;
                  count++;
          }
          *listp = list;
          *countp = count;
  
          return (0);
  }
  
  /**
   * @brief Get the number of devices in a devclass
   *
   * @param dc            the devclass to examine
   */
  int
  devclass_get_count(devclass_t dc)
  {
          int count, i;
  
          count = 0;
          for (i = 0; i < dc->maxunit; i++)
                  if (dc->devices[i])
                          count++;
          return (count);
  }
  
  /**
   * @brief Get the maximum unit number used in a devclass
   *
   * Note that this is one greater than the highest currently-allocated
   * unit.  If a null devclass_t is passed in, -1 is returned to indicate
   * that not even the devclass has been allocated yet.
   *
   * @param dc            the devclass to examine
   */
  int
  devclass_get_maxunit(devclass_t dc)
  {
          if (dc == NULL)
                  return (-1);
          return (dc->maxunit);
  }
  
  /**
   * @brief Find a free unit number in a devclass
   *
   * This function searches for the first unused unit number greater
   * that or equal to @p unit.
   *
   * @param dc            the devclass to examine
   * @param unit          the first unit number to check
   */
  int
  devclass_find_free_unit(devclass_t dc, int unit)
  {
          if (dc == NULL)
                  return (unit);
          while (unit < dc->maxunit && dc->devices[unit] != NULL)
                  unit++;
          return (unit);
  }
  
  /**
   * @brief Set the parent of a devclass
   *
   * The parent class is normally initialised automatically by
   * DRIVER_MODULE().
   *
   * @param dc            the devclass to edit
   * @param pdc           the new parent devclass
   */
  void
  devclass_set_parent(devclass_t dc, devclass_t pdc)
  {
          dc->parent = pdc;
  }
  
  /**
   * @brief Get the parent of a devclass
   *
   * @param dc            the devclass to examine
   */
  devclass_t
  devclass_get_parent(devclass_t dc)
  {
          return (dc->parent);
  }
  
  struct sysctl_ctx_list *
  devclass_get_sysctl_ctx(devclass_t dc)
  {
          return (&dc->sysctl_ctx);
  }
  
  struct sysctl_oid *
  devclass_get_sysctl_tree(devclass_t dc)
  {
          return (dc->sysctl_tree);
  }
  
  /**
   * @internal
   * @brief Allocate a unit number
   *
   * On entry, @p *unitp is the desired unit number (or @c -1 if any
   * will do). The allocated unit number is returned in @p *unitp.
  
   * @param dc            the devclass to allocate from
   * @param unitp         points at the location for the allocated unit
   *                      number
   *
   * @retval 0            success
   * @retval EEXIST       the requested unit number is already allocated
   * @retval ENOMEM       memory allocation failure
   */
  static int
  devclass_alloc_unit(devclass_t dc, device_t dev, int *unitp)
  {
          const char *s;
          int unit = *unitp;
  
          PDEBUG(("unit %d in devclass %s", unit, DEVCLANAME(dc)));
  
          /* Ask the parent bus if it wants to wire this device. */
          if (unit == -1)
                  BUS_HINT_DEVICE_UNIT(device_get_parent(dev), dev, dc->name,
                      &unit);
  
          /* If we were given a wired unit number, check for existing device */
          /* XXX imp XXX */
          if (unit != -1) {
                  if (unit >= 0 && unit < dc->maxunit &&
                      dc->devices[unit] != NULL) {
                          if (bootverbose)
                                  printf("%s: %s%d already exists; skipping it\n",
                                      dc->name, dc->name, *unitp);
                          return (EEXIST);
                  }
          } else {
                  /* Unwired device, find the next available slot for it */
                  unit = 0;
                  for (unit = 0;; unit++) {
                          /* If this device slot is already in use, skip it. */
                          if (unit < dc->maxunit && dc->devices[unit] != NULL)
                                  continue;
  
                          /* If there is an "at" hint for a unit then skip it. */
                          if (resource_string_value(dc->name, unit, "at", &s) ==
                              0)
                                  continue;
  
                          break;
                  }
          }
  
          /*
           * We've selected a unit beyond the length of the table, so let's
           * extend the table to make room for all units up to and including
           * this one.
           */
          if (unit >= dc->maxunit) {
                  device_t *newlist, *oldlist;
                  int newsize;
  
                  oldlist = dc->devices;
                  newsize = roundup((unit + 1),
                      MAX(1, MINALLOCSIZE / sizeof(device_t)));
                  newlist = malloc(sizeof(device_t) * newsize, M_BUS, M_NOWAIT);
                  if (!newlist)
                          return (ENOMEM);
                  if (oldlist != NULL)
                          bcopy(oldlist, newlist, sizeof(device_t) * dc->maxunit);
                  bzero(newlist + dc->maxunit,
                      sizeof(device_t) * (newsize - dc->maxunit));
                  dc->devices = newlist;
                  dc->maxunit = newsize;
                  if (oldlist != NULL)
                          free(oldlist, M_BUS);
          }
          PDEBUG(("now: unit %d in devclass %s", unit, DEVCLANAME(dc)));
  
          *unitp = unit;
          return (0);
  }
  
  /**
   * @internal
   * @brief Add a device to a devclass
   *
   * A unit number is allocated for the device (using the device's
   * preferred unit number if any) and the device is registered in the
   * devclass. This allows the device to be looked up by its unit
   * number, e.g. by decoding a dev_t minor number.
   *
   * @param dc            the devclass to add to
   * @param dev           the device to add
   *
   * @retval 0            success
   * @retval EEXIST       the requested unit number is already allocated
   * @retval ENOMEM       memory allocation failure
   */
  static int
  devclass_add_device(devclass_t dc, device_t dev)
  {
          int buflen, error;
  
          PDEBUG(("%s in devclass %s", DEVICENAME(dev), DEVCLANAME(dc)));
  
          buflen = snprintf(NULL, 0, "%s%d$", dc->name, INT_MAX);
          if (buflen < 0)
                  return (ENOMEM);
          dev->nameunit = malloc(buflen, M_BUS, M_NOWAIT|M_ZERO);
          if (!dev->nameunit)
                  return (ENOMEM);
  
          if ((error = devclass_alloc_unit(dc, dev, &dev->unit)) != 0) {
                  free(dev->nameunit, M_BUS);
                  dev->nameunit = NULL;
                  return (error);
          }
          dc->devices[dev->unit] = dev;
          dev->devclass = dc;
          snprintf(dev->nameunit, buflen, "%s%d", dc->name, dev->unit);
  
          return (0);
  }
  
  /**
   * @internal
   * @brief Delete a device from a devclass
   *
   * The device is removed from the devclass's device list and its unit
   * number is freed.
  
   * @param dc            the devclass to delete from
   * @param dev           the device to delete
   *
   * @retval 0            success
   */
  static int
  devclass_delete_device(devclass_t dc, device_t dev)
  {
          if (!dc || !dev)
                  return (0);
  
          PDEBUG(("%s in devclass %s", DEVICENAME(dev), DEVCLANAME(dc)));
  
          if (dev->devclass != dc || dc->devices[dev->unit] != dev)
                  panic("devclass_delete_device: inconsistent device class");
          dc->devices[dev->unit] = NULL;
          if (dev->flags & DF_WILDCARD)
                  dev->unit = -1;
          dev->devclass = NULL;
          free(dev->nameunit, M_BUS);
          dev->nameunit = NULL;
  
          return (0);
  }
  
  /**
   * @internal
   * @brief Make a new device and add it as a child of @p parent
   *
   * @param parent        the parent of the new device
   * @param name          the devclass name of the new device or @c NULL
   *                      to leave the devclass unspecified
   * @parem unit          the unit number of the new device of @c -1 to
   *                      leave the unit number unspecified
   *
   * @returns the new device
   */
  static device_t
  make_device(device_t parent, const char *name, int unit)
  {
          device_t dev;
          devclass_t dc;
  
          PDEBUG(("%s at %s as unit %d", name, DEVICENAME(parent), unit));
  
          if (name) {
                  dc = devclass_find_internal(name, NULL, TRUE);
                  if (!dc) {
                          printf("make_device: can't find device class %s\n",
                              name);
                          return (NULL);
                  }
          } else {
                  dc = NULL;
          }
  
          dev = malloc(sizeof(*dev), M_BUS, M_NOWAIT|M_ZERO);
          if (!dev)
                  return (NULL);
  
          dev->parent = parent;
          TAILQ_INIT(&dev->children);
          kobj_init((kobj_t) dev, &null_class);
          dev->driver = NULL;
          dev->devclass = NULL;
          dev->unit = unit;
          dev->nameunit = NULL;
          dev->desc = NULL;
          dev->busy = 0;
          dev->devflags = 0;
          dev->flags = DF_ENABLED;
          dev->order = 0;
          if (unit == -1)
                  dev->flags |= DF_WILDCARD;
          if (name) {
                  dev->flags |= DF_FIXEDCLASS;
                  if (devclass_add_device(dc, dev)) {
                          kobj_delete((kobj_t) dev, M_BUS);
                          return (NULL);
                  }
          }
          if (parent != NULL && device_has_quiet_children(parent))
                  dev->flags |= DF_QUIET | DF_QUIET_CHILDREN;
          dev->ivars = NULL;
          dev->softc = NULL;
  
          dev->state = DS_NOTPRESENT;
  
          TAILQ_INSERT_TAIL(&bus_data_devices, dev, devlink);
          bus_data_generation_update();
  
          return (dev);
  }
  
  /**
   * @internal
   * @brief Print a description of a device.
   */
  static int
  device_print_child(device_t dev, device_t child)
  {
          int retval = 0;
  
          if (device_is_alive(child))
                  retval += BUS_PRINT_CHILD(dev, child);
          else
                  retval += device_printf(child, " not found\n");
  
          return (retval);
  }
  
  /**
   * @brief Create a new device
   *
   * This creates a new device and adds it as a child of an existing
   * parent device. The new device will be added after the last existing
   * child with order zero.
   *
   * @param dev           the device which will be the parent of the
   *                      new child device
   * @param name          devclass name for new device or @c NULL if not
   *                      specified
   * @param unit          unit number for new device or @c -1 if not
   *                      specified
   *
   * @returns             the new device
   */
  device_t
  device_add_child(device_t dev, const char *name, int unit)
  {
          return (device_add_child_ordered(dev, 0, name, unit));
  }
  
  /**
   * @brief Create a new device
   *
   * This creates a new device and adds it as a child of an existing
   * parent device. The new device will be added after the last existing
   * child with the same order.
   *
   * @param dev           the device which will be the parent of the
   *                      new child device
   * @param order         a value which is used to partially sort the
   *                      children of @p dev - devices created using
   *                      lower values of @p order appear first in @p
   *                      dev's list of children
   * @param name          devclass name for new device or @c NULL if not
   *                      specified
   * @param unit          unit number for new device or @c -1 if not
   *                      specified
   *
   * @returns             the new device
   */
  device_t
  device_add_child_ordered(device_t dev, u_int order, const char *name, int unit)
  {
          device_t child;
          device_t place;
  
          PDEBUG(("%s at %s with order %u as unit %d",
              name, DEVICENAME(dev), order, unit));
          KASSERT(name != NULL || unit == -1,
              ("child device with wildcard name and specific unit number"));
  
          child = make_device(dev, name, unit);
          if (child == NULL)
                  return (child);
          child->order = order;
  
          TAILQ_FOREACH(place, &dev->children, link) {
                  if (place->order > order)
                          break;
          }
  
          if (place) {
                  /*
                   * The device 'place' is the first device whose order is
                   * greater than the new child.
                   */
                  TAILQ_INSERT_BEFORE(place, child, link);
          } else {
                  /*
                   * The new child's order is greater or equal to the order of
                   * any existing device. Add the child to the tail of the list.
                   */
                  TAILQ_INSERT_TAIL(&dev->children, child, link);
          }
  
          bus_data_generation_update();
          return (child);
  }
  
  /**
   * @brief Delete a device
   *
   * This function deletes a device along with all of its children. If
   * the device currently has a driver attached to it, the device is
   * detached first using device_detach().
   *
   * @param dev           the parent device
   * @param child         the device to delete
   *
   * @retval 0            success
   * @retval non-zero     a unit error code describing the error
   */
  int
  device_delete_child(device_t dev, device_t child)
  {
          int error;
          device_t grandchild;
  
          PDEBUG(("%s from %s", DEVICENAME(child), DEVICENAME(dev)));
  
          /* detach parent before deleting children, if any */
          if ((error = device_detach(child)) != 0)
                  return (error);
  
          /* remove children second */
          while ((grandchild = TAILQ_FIRST(&child->children)) != NULL) {
                  error = device_delete_child(child, grandchild);
                  if (error)
                          return (error);
          }
  
          if (child->devclass)
                  devclass_delete_device(child->devclass, child);
          if (child->parent)
                  BUS_CHILD_DELETED(dev, child);
          TAILQ_REMOVE(&dev->children, child, link);
          TAILQ_REMOVE(&bus_data_devices, child, devlink);
          kobj_delete((kobj_t) child, M_BUS);
  
          bus_data_generation_update();
          return (0);
  }
  
  /**
   * @brief Delete all children devices of the given device, if any.
   *
   * This function deletes all children devices of the given device, if
   * any, using the device_delete_child() function for each device it
   * finds. If a child device cannot be deleted, this function will
   * return an error code.
   *
   * @param dev           the parent device
   *
   * @retval 0            success
   * @retval non-zero     a device would not detach
   */
  int
  device_delete_children(device_t dev)
  {
          device_t child;
          int error;
  
          PDEBUG(("Deleting all children of %s", DEVICENAME(dev)));
  
          error = 0;
  
          while ((child = TAILQ_FIRST(&dev->children)) != NULL) {
                  error = device_delete_child(dev, child);
                  if (error) {
                          PDEBUG(("Failed deleting %s", DEVICENAME(child)));
                          break;
                  }
          }
          return (error);
  }
  
  /**
   * @brief Find a device given a unit number
   *
   * This is similar to devclass_get_devices() but only searches for
   * devices which have @p dev as a parent.
   *
   * @param dev           the parent device to search
   * @param unit          the unit number to search for.  If the unit is -1,
   *                      return the first child of @p dev which has name
   *                      @p classname (that is, the one with the lowest unit.)
   *
   * @returns             the device with the given unit number or @c
   *                      NULL if there is no such device
   */
  device_t
  device_find_child(device_t dev, const char *classname, int unit)
  {
          devclass_t dc;
          device_t child;
  
          dc = devclass_find(classname);
          if (!dc)
                  return (NULL);
  
          if (unit != -1) {
                  child = devclass_get_device(dc, unit);
                  if (child && child->parent == dev)
                          return (child);
          } else {
                  for (unit = 0; unit < devclass_get_maxunit(dc); unit++) {
                          child = devclass_get_device(dc, unit);
                          if (child && child->parent == dev)
                                  return (child);
                  }
          }
          return (NULL);
  }
  
  /**
   * @internal
   */
  static driverlink_t
  first_matching_driver(devclass_t dc, device_t dev)
  {
          if (dev->devclass)
                  return (devclass_find_driver_internal(dc, dev->devclass->name));
          return (TAILQ_FIRST(&dc->drivers));
  }
  
  /**
   * @internal
   */
  static driverlink_t
  next_matching_driver(devclass_t dc, device_t dev, driverlink_t last)
  {
          if (dev->devclass) {
                  driverlink_t dl;
                  for (dl = TAILQ_NEXT(last, link); dl; dl = TAILQ_NEXT(dl, link))
                          if (!strcmp(dev->devclass->name, dl->driver->name))
                                  return (dl);
                  return (NULL);
          }
          return (TAILQ_NEXT(last, link));
  }
  
  /**
   * @internal
   */
  int
  device_probe_child(device_t dev, device_t child)
  {
          devclass_t dc;
          driverlink_t best = NULL;
          driverlink_t dl;
          int result, pri = 0;
          /* We should preserve the devclass (or lack of) set by the bus. */
          int hasclass = (child->devclass != NULL);
  
          bus_topo_assert();
  
          dc = dev->devclass;
          if (!dc)
                  panic("device_probe_child: parent device has no devclass");
  
          /*
           * If the state is already probed, then return.
           */
          if (child->state == DS_ALIVE)
                  return (0);
  
          for (; dc; dc = dc->parent) {
                  for (dl = first_matching_driver(dc, child);
                       dl;
                       dl = next_matching_driver(dc, child, dl)) {
                          /* If this driver's pass is too high, then ignore it. */
                          if (dl->pass > bus_current_pass)
                                  continue;
  
                          PDEBUG(("Trying %s", DRIVERNAME(dl->driver)));
                          result = device_set_driver(child, dl->driver);
                          if (result == ENOMEM)
                                  return (result);
                          else if (result != 0)
                                  continue;
                          if (!hasclass) {
                                  if (device_set_devclass(child,
                                      dl->driver->name) != 0) {
                                          char const * devname =
                                              device_get_name(child);
                                          if (devname == NULL)
                                                  devname = "(unknown)";
                                          printf("driver bug: Unable to set "
                                              "devclass (class: %s "
                                              "devname: %s)\n",
                                              dl->driver->name,
                                              devname);
                                          (void)device_set_driver(child, NULL);
                                          continue;
                                  }
                          }
  
                          /* Fetch any flags for the device before probing. */
                          resource_int_value(dl->driver->name, child->unit,
                              "flags", &child->devflags);
  
                          result = DEVICE_PROBE(child);
  
                          /*
                           * If the driver returns SUCCESS, there can be
                           * no higher match for this device.
                           */
                          if (result == 0) {
                                  best = dl;
                                  pri = 0;
                                  break;
                          }
  
                          /* Reset flags and devclass before the next probe. */
                          child->devflags = 0;
                          if (!hasclass)
                                  (void)device_set_devclass(child, NULL);
  
                          /*
                           * Reset DF_QUIET in case this driver doesn't
                           * end up as the best driver.
                           */
                          device_verbose(child);
  
                          /*
                           * Probes that return BUS_PROBE_NOWILDCARD or lower
                           * only match on devices whose driver was explicitly
                           * specified.
                           */
                          if (result <= BUS_PROBE_NOWILDCARD &&
                              !(child->flags & DF_FIXEDCLASS)) {
                                  result = ENXIO;
                          }
  
                          /*
                           * The driver returned an error so it
                           * certainly doesn't match.
                           */
                          if (result > 0) {
                                  (void)device_set_driver(child, NULL);
                                  continue;
                          }
  
                          /*
                           * A priority lower than SUCCESS, remember the
                           * best matching driver. Initialise the value
                           * of pri for the first match.
                           */
                          if (best == NULL || result > pri) {
                                  best = dl;
                                  pri = result;
                                  continue;
                          }
                  }
                  /*
                   * If we have an unambiguous match in this devclass,
                   * don't look in the parent.
                   */
                  if (best && pri == 0)
                          break;
          }
  
          if (best == NULL)
                  return (ENXIO);
  
          /*
           * If we found a driver, change state and initialise the devclass.
           */
          if (pri < 0) {
                  /* Set the winning driver, devclass, and flags. */
                  result = device_set_driver(child, best->driver);
                  if (result != 0)
                          return (result);
                  if (!child->devclass) {
                          result = device_set_devclass(child, best->driver->name);
                          if (result != 0) {
                                  (void)device_set_driver(child, NULL);
                                  return (result);
                          }
                  }
                  resource_int_value(best->driver->name, child->unit,
                      "flags", &child->devflags);
  
                  /*
                   * A bit bogus. Call the probe method again to make sure
                   * that we have the right description.
                   */
                  result = DEVICE_PROBE(child);
                  if (result > 0) {
                          if (!hasclass)
                                  (void)device_set_devclass(child, NULL);
                          (void)device_set_driver(child, NULL);
                          return (result);
                  }
          }
  
          child->state = DS_ALIVE;
          bus_data_generation_update();
          return (0);
  }
  
  /**
   * @brief Return the parent of a device
   */
  device_t
  device_get_parent(device_t dev)
  {
          return (dev->parent);
  }
  
  /**
   * @brief Get a list of children of a device
   *
   * An array containing a list of all the children of the given device
   * is allocated and returned in @p *devlistp. The number of devices
   * in the array is returned in @p *devcountp. The caller should free
   * the array using @c free(p, M_TEMP).
   *
   * @param dev           the device to examine
   * @param devlistp      points at location for array pointer return
   *                      value
   * @param devcountp     points at location for array size return value
   *
   * @retval 0            success
   * @retval ENOMEM       the array allocation failed
   */
  int
  device_get_children(device_t dev, device_t **devlistp, int *devcountp)
  {
          int count;
          device_t child;
          device_t *list;
  
          count = 0;
          TAILQ_FOREACH(child, &dev->children, link) {
                  count++;
          }
          if (count == 0) {
                  *devlistp = NULL;
                  *devcountp = 0;
                  return (0);
          }
  
          list = malloc(count * sizeof(device_t), M_TEMP, M_NOWAIT|M_ZERO);
          if (!list)
                  return (ENOMEM);
  
          count = 0;
          TAILQ_FOREACH(child, &dev->children, link) {
                  list[count] = child;
                  count++;
          }
  
          *devlistp = list;
          *devcountp = count;
  
          return (0);
  }
  
  /**
   * @brief Return the current driver for the device or @c NULL if there
   * is no driver currently attached
   */
  driver_t *
  device_get_driver(device_t dev)
  {
          return (dev->driver);
  }
  
  /**
   * @brief Return the current devclass for the device or @c NULL if
   * there is none.
   */
  devclass_t
  device_get_devclass(device_t dev)
  {
          return (dev->devclass);
  }
  
  /**
   * @brief Return the name of the device's devclass or @c NULL if there
   * is none.
   */
  const char *
  device_get_name(device_t dev)
  {
          if (dev != NULL && dev->devclass)
                  return (devclass_get_name(dev->devclass));
          return (NULL);
  }
  
  /**
   * @brief Return a string containing the device's devclass name
   * followed by an ascii representation of the device's unit number
   * (e.g. @c "foo2").
   */
  const char *
  device_get_nameunit(device_t dev)
  {
          return (dev->nameunit);
  }
  
  /**
   * @brief Return the device's unit number.
   */
  int
  device_get_unit(device_t dev)
  {
          return (dev->unit);
  }
  
  /**
   * @brief Return the device's description string
   */
  const char *
  device_get_desc(device_t dev)
  {
          return (dev->desc);
  }
  
  /**
   * @brief Return the device's flags
   */
  uint32_t
  device_get_flags(device_t dev)
  {
          return (dev->devflags);
  }
  
  struct sysctl_ctx_list *
  device_get_sysctl_ctx(device_t dev)
  {
          return (&dev->sysctl_ctx);
  }
  
  struct sysctl_oid *
  device_get_sysctl_tree(device_t dev)
  {
          return (dev->sysctl_tree);
  }
  
  /**
   * @brief Print the name of the device followed by a colon and a space
   *
   * @returns the number of characters printed
   */
  int
  device_print_prettyname(device_t dev)
  {
          const char *name = device_get_name(dev);
  
          if (name == NULL)
                  return (printf("unknown: "));
          return (printf("%s%d: ", name, device_get_unit(dev)));
  }
  
  /**
   * @brief Print the name of the device followed by a colon, a space
   * and the result of calling vprintf() with the value of @p fmt and
   * the following arguments.
   *
   * @returns the number of characters printed
   */
  int
  device_printf(device_t dev, const char * fmt, ...)
  {
          char buf[128];
          struct sbuf sb;
          const char *name;
          va_list ap;
          size_t retval;
  
          retval = 0;
  
          sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
          sbuf_set_drain(&sb, sbuf_printf_drain, &retval);
  
          name = device_get_name(dev);
  
          if (name == NULL)
                  sbuf_cat(&sb, "unknown: ");
          else
                  sbuf_printf(&sb, "%s%d: ", name, device_get_unit(dev));
  
          va_start(ap, fmt);
          sbuf_vprintf(&sb, fmt, ap);
          va_end(ap);
  
          sbuf_finish(&sb);
          sbuf_delete(&sb);
  
          return (retval);
  }
  
  /**
   * @brief Print the name of the device followed by a colon, a space
   * and the result of calling log() with the value of @p fmt and
   * the following arguments.
   *
   * @returns the number of characters printed
   */
  int
  device_log(device_t dev, int pri, const char * fmt, ...)
  {
          char buf[128];
          struct sbuf sb;
          const char *name;
          va_list ap;
          size_t retval;
  
          retval = 0;
  
          sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
  
          name = device_get_name(dev);
  
          if (name == NULL)
                  sbuf_cat(&sb, "unknown: ");
          else
                  sbuf_printf(&sb, "%s%d: ", name, device_get_unit(dev));
  
          va_start(ap, fmt);
          sbuf_vprintf(&sb, fmt, ap);
          va_end(ap);
  
          sbuf_finish(&sb);
  
          log(pri, "%.*s", (int) sbuf_len(&sb), sbuf_data(&sb));
          retval = sbuf_len(&sb);
  
          sbuf_delete(&sb);
  
          return (retval);
  }
  
  /**
   * @internal
   */
  static void
  device_set_desc_internal(device_t dev, const char* desc, int copy)
  {
          if (dev->desc && (dev->flags & DF_DESCMALLOCED)) {
                  free(dev->desc, M_BUS);
                  dev->flags &= ~DF_DESCMALLOCED;
                  dev->desc = NULL;
          }
  
          if (copy && desc) {
                  dev->desc = malloc(strlen(desc) + 1, M_BUS, M_NOWAIT);
                  if (dev->desc) {
                          strcpy(dev->desc, desc);
                          dev->flags |= DF_DESCMALLOCED;
                  }
          } else {
                  /* Avoid a -Wcast-qual warning */
                  dev->desc = (char *)(uintptr_t) desc;
          }
  
          bus_data_generation_update();
  }
  
  /**
   * @brief Set the device's description
   *
   * The value of @c desc should be a string constant that will not
   * change (at least until the description is changed in a subsequent
   * call to device_set_desc() or device_set_desc_copy()).
   */
  void
  device_set_desc(device_t dev, const char* desc)
  {
          device_set_desc_internal(dev, desc, FALSE);
  }
  
  /**
   * @brief Set the device's description
   *
   * The string pointed to by @c desc is copied. Use this function if
   * the device description is generated, (e.g. with sprintf()).
   */
  void
  device_set_desc_copy(device_t dev, const char* desc)
  {
          device_set_desc_internal(dev, desc, TRUE);
  }
  
  /**
   * @brief Set the device's flags
   */
  void
  device_set_flags(device_t dev, uint32_t flags)
  {
          dev->devflags = flags;
  }
  
  /**
   * @brief Return the device's softc field
   *
   * The softc is allocated and zeroed when a driver is attached, based
   * on the size field of the driver.
   */
  void *
  device_get_softc(device_t dev)
  {
          return (dev->softc);
  }
  
  /**
   * @brief Set the device's softc field
   *
   * Most drivers do not need to use this since the softc is allocated
   * automatically when the driver is attached.
   */
  void
  device_set_softc(device_t dev, void *softc)
  {
          if (dev->softc && !(dev->flags & DF_EXTERNALSOFTC))
                  free(dev->softc, M_BUS_SC);
          dev->softc = softc;
          if (dev->softc)
                  dev->flags |= DF_EXTERNALSOFTC;
          else
                  dev->flags &= ~DF_EXTERNALSOFTC;
  }
  
  /**
   * @brief Free claimed softc
   *
   * Most drivers do not need to use this since the softc is freed
   * automatically when the driver is detached.
   */
  void
  device_free_softc(void *softc)
  {
          free(softc, M_BUS_SC);
  }
  
  /**
   * @brief Claim softc
   *
   * This function can be used to let the driver free the automatically
   * allocated softc using "device_free_softc()". This function is
   * useful when the driver is refcounting the softc and the softc
   * cannot be freed when the "device_detach" method is called.
   */
  void
  device_claim_softc(device_t dev)
  {
          if (dev->softc)
                  dev->flags |= DF_EXTERNALSOFTC;
          else
                  dev->flags &= ~DF_EXTERNALSOFTC;
  }
  
  /**
   * @brief Get the device's ivars field
   *
   * The ivars field is used by the parent device to store per-device
   * state (e.g. the physical location of the device or a list of
   * resources).
   */
  void *
  device_get_ivars(device_t dev)
  {
          KASSERT(dev != NULL, ("device_get_ivars(NULL, ...)"));
          return (dev->ivars);
  }
  
  /**
   * @brief Set the device's ivars field
   */
  void
  device_set_ivars(device_t dev, void * ivars)
  {
          KASSERT(dev != NULL, ("device_set_ivars(NULL, ...)"));
          dev->ivars = ivars;
  }
  
  /**
   * @brief Return the device's state
   */
  device_state_t
  device_get_state(device_t dev)
  {
          return (dev->state);
  }
  
  /**
   * @brief Set the DF_ENABLED flag for the device
   */
  void
  device_enable(device_t dev)
  {
          dev->flags |= DF_ENABLED;
  }
  
  /**
   * @brief Clear the DF_ENABLED flag for the device
   */
  void
  device_disable(device_t dev)
  {
          dev->flags &= ~DF_ENABLED;
  }
  
  /**
   * @brief Increment the busy counter for the device
   */
  void
  device_busy(device_t dev)
  {
  
          /*
           * Mark the device as busy, recursively up the tree if this busy count
           * goes 0->1.
           */
          if (refcount_acquire(&dev->busy) == 0 && dev->parent != NULL)
                  device_busy(dev->parent);
  }
  
  /**
   * @brief Decrement the busy counter for the device
   */
  void
  device_unbusy(device_t dev)
  {
  
          /*
           * Mark the device as unbsy, recursively if this is the last busy count.
           */
          if (refcount_release(&dev->busy) && dev->parent != NULL)
                  device_unbusy(dev->parent);
  }
  
  /**
   * @brief Set the DF_QUIET flag for the device
   */
  void
  device_quiet(device_t dev)
  {
          dev->flags |= DF_QUIET;
  }
  
  /**
   * @brief Set the DF_QUIET_CHILDREN flag for the device
   */
  void
  device_quiet_children(device_t dev)
  {
          dev->flags |= DF_QUIET_CHILDREN;
  }
  
  /**
   * @brief Clear the DF_QUIET flag for the device
   */
  void
  device_verbose(device_t dev)
  {
          dev->flags &= ~DF_QUIET;
  }
  
  ssize_t
  device_get_property(device_t dev, const char *prop, void *val, size_t sz,
      device_property_type_t type)
  {
          device_t bus = device_get_parent(dev);
  
          switch (type) {
          case DEVICE_PROP_ANY:
          case DEVICE_PROP_BUFFER:
          case DEVICE_PROP_HANDLE:        /* Size checks done in implementation. */
                  break;
          case DEVICE_PROP_UINT32:
                  if (sz % 4 != 0)
                          return (-1);
                  break;
          case DEVICE_PROP_UINT64:
                  if (sz % 8 != 0)
                          return (-1);
                  break;
          default:
                  return (-1);
          }
  
          return (BUS_GET_PROPERTY(bus, dev, prop, val, sz, type));
  }
  
  bool
  device_has_property(device_t dev, const char *prop)
  {
          return (device_get_property(dev, prop, NULL, 0, DEVICE_PROP_ANY) >= 0);
  }
  
  /**
   * @brief Return non-zero if the DF_QUIET_CHIDLREN flag is set on the device
   */
  int
  device_has_quiet_children(device_t dev)
  {
          return ((dev->flags & DF_QUIET_CHILDREN) != 0);
  }
  
  /**
   * @brief Return non-zero if the DF_QUIET flag is set on the device
   */
  int
  device_is_quiet(device_t dev)
  {
          return ((dev->flags & DF_QUIET) != 0);
  }
  
  /**
   * @brief Return non-zero if the DF_ENABLED flag is set on the device
   */
  int
  device_is_enabled(device_t dev)
  {
          return ((dev->flags & DF_ENABLED) != 0);
  }
  
  /**
   * @brief Return non-zero if the device was successfully probed
   */
  int
  device_is_alive(device_t dev)
  {
          return (dev->state >= DS_ALIVE);
  }
  
  /**
   * @brief Return non-zero if the device currently has a driver
   * attached to it
   */
  int
  device_is_attached(device_t dev)
  {
          return (dev->state >= DS_ATTACHED);
  }
  
  /**
   * @brief Return non-zero if the device is currently suspended.
   */
  int
  device_is_suspended(device_t dev)
  {
          return ((dev->flags & DF_SUSPENDED) != 0);
  }
  
  /**
   * @brief Set the devclass of a device
   * @see devclass_add_device().
   */
  int
  device_set_devclass(device_t dev, const char *classname)
  {
          devclass_t dc;
          int error;
  
          if (!classname) {
                  if (dev->devclass)
                          devclass_delete_device(dev->devclass, dev);
                  return (0);
          }
  
          if (dev->devclass) {
                  printf("device_set_devclass: device class already set\n");
                  return (EINVAL);
          }
  
          dc = devclass_find_internal(classname, NULL, TRUE);
          if (!dc)
                  return (ENOMEM);
  
          error = devclass_add_device(dc, dev);
  
          bus_data_generation_update();
          return (error);
  }
  
  /**
   * @brief Set the devclass of a device and mark the devclass fixed.
   * @see device_set_devclass()
   */
  int
  device_set_devclass_fixed(device_t dev, const char *classname)
  {
          int error;
  
          if (classname == NULL)
                  return (EINVAL);
  
          error = device_set_devclass(dev, classname);
          if (error)
                  return (error);
          dev->flags |= DF_FIXEDCLASS;
          return (0);
  }
  
  /**
   * @brief Query the device to determine if it's of a fixed devclass
   * @see device_set_devclass_fixed()
   */
  bool
  device_is_devclass_fixed(device_t dev)
  {
          return ((dev->flags & DF_FIXEDCLASS) != 0);
  }
  
  /**
   * @brief Set the driver of a device
   *
   * @retval 0            success
   * @retval EBUSY        the device already has a driver attached
   * @retval ENOMEM       a memory allocation failure occurred
   */
  int
  device_set_driver(device_t dev, driver_t *driver)
  {
          int domain;
          struct domainset *policy;
  
          if (dev->state >= DS_ATTACHED)
                  return (EBUSY);
  
          if (dev->driver == driver)
                  return (0);
  
          if (dev->softc && !(dev->flags & DF_EXTERNALSOFTC)) {
                  free(dev->softc, M_BUS_SC);
                  dev->softc = NULL;
          }
          device_set_desc(dev, NULL);
          kobj_delete((kobj_t) dev, NULL);
          dev->driver = driver;
          if (driver) {
                  kobj_init((kobj_t) dev, (kobj_class_t) driver);
                  if (!(dev->flags & DF_EXTERNALSOFTC) && driver->size > 0) {
                          if (bus_get_domain(dev, &domain) == 0)
                                  policy = DOMAINSET_PREF(domain);
                          else
                                  policy = DOMAINSET_RR();
                          dev->softc = malloc_domainset(driver->size, M_BUS_SC,
                              policy, M_NOWAIT | M_ZERO);
                          if (!dev->softc) {
                                  kobj_delete((kobj_t) dev, NULL);
                                  kobj_init((kobj_t) dev, &null_class);
                                  dev->driver = NULL;
                                  return (ENOMEM);
                          }
                  }
          } else {
                  kobj_init((kobj_t) dev, &null_class);
          }
  
          bus_data_generation_update();
          return (0);
  }
  
  /**
   * @brief Probe a device, and return this status.
   *
   * This function is the core of the device autoconfiguration
   * system. Its purpose is to select a suitable driver for a device and
   * then call that driver to initialise the hardware appropriately. The
   * driver is selected by calling the DEVICE_PROBE() method of a set of
   * candidate drivers and then choosing the driver which returned the
   * best value. This driver is then attached to the device using
   * device_attach().
   *
   * The set of suitable drivers is taken from the list of drivers in
   * the parent device's devclass. If the device was originally created
   * with a specific class name (see device_add_child()), only drivers
   * with that name are probed, otherwise all drivers in the devclass
   * are probed. If no drivers return successful probe values in the
   * parent devclass, the search continues in the parent of that
   * devclass (see devclass_get_parent()) if any.
   *
   * @param dev           the device to initialise
   *
   * @retval 0            success
   * @retval ENXIO        no driver was found
   * @retval ENOMEM       memory allocation failure
   * @retval non-zero     some other unix error code
   * @retval -1           Device already attached
   */
  int
  device_probe(device_t dev)
  {
          int error;
  
          bus_topo_assert();
  
          if (dev->state >= DS_ALIVE)
                  return (-1);
  
          if (!(dev->flags & DF_ENABLED)) {
                  if (bootverbose && device_get_name(dev) != NULL) {
                          device_print_prettyname(dev);
                          printf("not probed (disabled)\n");
                  }
                  return (-1);
          }
          if ((error = device_probe_child(dev->parent, dev)) != 0) {
                  if (bus_current_pass == BUS_PASS_DEFAULT &&
                      !(dev->flags & DF_DONENOMATCH)) {
                          device_handle_nomatch(dev);
                  }
                  return (error);
          }
          return (0);
  }
  
  /**
   * @brief Probe a device and attach a driver if possible
   *
   * calls device_probe() and attaches if that was successful.
   */
  int
  device_probe_and_attach(device_t dev)
  {
          int error;
  
          bus_topo_assert();
  
          error = device_probe(dev);
          if (error == -1)
                  return (0);
          else if (error != 0)
                  return (error);
  
          CURVNET_SET_QUIET(vnet0);
          error = device_attach(dev);
          CURVNET_RESTORE();
          return error;
  }
  
  /**
   * @brief Attach a device driver to a device
   *
   * This function is a wrapper around the DEVICE_ATTACH() driver
   * method. In addition to calling DEVICE_ATTACH(), it initialises the
   * device's sysctl tree, optionally prints a description of the device
   * and queues a notification event for user-based device management
   * services.
   *
   * Normally this function is only called internally from
   * device_probe_and_attach().
   *
   * @param dev           the device to initialise
   *
   * @retval 0            success
   * @retval ENXIO        no driver was found
   * @retval ENOMEM       memory allocation failure
   * @retval non-zero     some other unix error code
   */
  int
  device_attach(device_t dev)
  {
          uint64_t attachtime;
          uint16_t attachentropy;
          int error;
  
          if (resource_disabled(dev->driver->name, dev->unit)) {
                  device_disable(dev);
                  if (bootverbose)
                           device_printf(dev, "disabled via hints entry\n");
                  return (ENXIO);
          }
  
          device_sysctl_init(dev);
          if (!device_is_quiet(dev))
                  device_print_child(dev->parent, dev);
          attachtime = get_cyclecount();
          dev->state = DS_ATTACHING;
          if ((error = DEVICE_ATTACH(dev)) != 0) {
                  printf("device_attach: %s%d attach returned %d\n",
                      dev->driver->name, dev->unit, error);
                  if (disable_failed_devs) {
                          /*
                           * When the user has asked to disable failed devices, we
                           * directly disable the device, but leave it in the
                           * attaching state. It will not try to probe/attach the
                           * device further. This leaves the device numbering
                           * intact for other similar devices in the system. It
                           * can be removed from this state with devctl.
                           */
                          device_disable(dev);
                  } else {
                          /*
                           * Otherwise, when attach fails, tear down the state
                           * around that so we can retry when, for example, new
                           * drivers are loaded.
                           */
                          if (!(dev->flags & DF_FIXEDCLASS))
                                  devclass_delete_device(dev->devclass, dev);
                          (void)device_set_driver(dev, NULL);
                          device_sysctl_fini(dev);
                          KASSERT(dev->busy == 0, ("attach failed but busy"));
                          dev->state = DS_NOTPRESENT;
                  }
                  return (error);
          }
          dev->flags |= DF_ATTACHED_ONCE;
          /*
           * We only need the low bits of this time, but ranges from tens to thousands
           * have been seen, so keep 2 bytes' worth.
           */
          attachentropy = (uint16_t)(get_cyclecount() - attachtime);
          random_harvest_direct(&attachentropy, sizeof(attachentropy), RANDOM_ATTACH);
          device_sysctl_update(dev);
          dev->state = DS_ATTACHED;
          dev->flags &= ~DF_DONENOMATCH;
          EVENTHANDLER_DIRECT_INVOKE(device_attach, dev);
          return (0);
  }
  
  /**
   * @brief Detach a driver from a device
   *
   * This function is a wrapper around the DEVICE_DETACH() driver
   * method. If the call to DEVICE_DETACH() succeeds, it calls
   * BUS_CHILD_DETACHED() for the parent of @p dev, queues a
   * notification event for user-based device management services and
   * cleans up the device's sysctl tree.
   *
   * @param dev           the device to un-initialise
   *
   * @retval 0            success
   * @retval ENXIO        no driver was found
   * @retval ENOMEM       memory allocation failure
   * @retval non-zero     some other unix error code
   */
  int
  device_detach(device_t dev)
  {
          int error;
  
          bus_topo_assert();
  
          PDEBUG(("%s", DEVICENAME(dev)));
          if (dev->busy > 0)
                  return (EBUSY);
          if (dev->state == DS_ATTACHING) {
                  device_printf(dev, "device in attaching state! Deferring detach.\n");
                  return (EBUSY);
          }
          if (dev->state != DS_ATTACHED)
                  return (0);
  
          EVENTHANDLER_DIRECT_INVOKE(device_detach, dev, EVHDEV_DETACH_BEGIN);
          if ((error = DEVICE_DETACH(dev)) != 0) {
                  EVENTHANDLER_DIRECT_INVOKE(device_detach, dev,
                      EVHDEV_DETACH_FAILED);
                  return (error);
          } else {
                  EVENTHANDLER_DIRECT_INVOKE(device_detach, dev,
                      EVHDEV_DETACH_COMPLETE);
          }
          if (!device_is_quiet(dev))
                  device_printf(dev, "detached\n");
          if (dev->parent)
                  BUS_CHILD_DETACHED(dev->parent, dev);
  
          if (!(dev->flags & DF_FIXEDCLASS))
                  devclass_delete_device(dev->devclass, dev);
  
          device_verbose(dev);
          dev->state = DS_NOTPRESENT;
          (void)device_set_driver(dev, NULL);
          device_sysctl_fini(dev);
  
          return (0);
  }
  
  /**
   * @brief Tells a driver to quiesce itself.
   *
   * This function is a wrapper around the DEVICE_QUIESCE() driver
   * method. If the call to DEVICE_QUIESCE() succeeds.
   *
   * @param dev           the device to quiesce
   *
   * @retval 0            success
   * @retval ENXIO        no driver was found
   * @retval ENOMEM       memory allocation failure
   * @retval non-zero     some other unix error code
   */
  int
  device_quiesce(device_t dev)
  {
          PDEBUG(("%s", DEVICENAME(dev)));
          if (dev->busy > 0)
                  return (EBUSY);
          if (dev->state != DS_ATTACHED)
                  return (0);
  
          return (DEVICE_QUIESCE(dev));
  }
  
  /**
   * @brief Notify a device of system shutdown
   *
   * This function calls the DEVICE_SHUTDOWN() driver method if the
   * device currently has an attached driver.
   *
   * @returns the value returned by DEVICE_SHUTDOWN()
   */
  int
  device_shutdown(device_t dev)
  {
          if (dev->state < DS_ATTACHED)
                  return (0);
          return (DEVICE_SHUTDOWN(dev));
  }
  
  /**
   * @brief Set the unit number of a device
   *
   * This function can be used to override the unit number used for a
   * device (e.g. to wire a device to a pre-configured unit number).
   */
  int
  device_set_unit(device_t dev, int unit)
  {
          devclass_t dc;
          int err;
  
          if (unit == dev->unit)
                  return (0);
          dc = device_get_devclass(dev);
          if (unit < dc->maxunit && dc->devices[unit])
                  return (EBUSY);
          err = devclass_delete_device(dc, dev);
          if (err)
                  return (err);
          dev->unit = unit;
          err = devclass_add_device(dc, dev);
          if (err)
                  return (err);
  
          bus_data_generation_update();
          return (0);
  }
  
  /*======================================*/
  /*
   * Some useful method implementations to make life easier for bus drivers.
   */
  
  void
  resource_init_map_request_impl(struct resource_map_request *args, size_t sz)
  {
          bzero(args, sz);
          args->size = sz;
          args->memattr = VM_MEMATTR_DEVICE;
  }
  
  /**
   * @brief Initialise a resource list.
   *
   * @param rl            the resource list to initialise
   */
  void
  resource_list_init(struct resource_list *rl)
  {
          STAILQ_INIT(rl);
  }
  
  /**
   * @brief Reclaim memory used by a resource list.
   *
   * This function frees the memory for all resource entries on the list
   * (if any).
   *
   * @param rl            the resource list to free
   */
  void
  resource_list_free(struct resource_list *rl)
  {
          struct resource_list_entry *rle;
  
          while ((rle = STAILQ_FIRST(rl)) != NULL) {
                  if (rle->res)
                          panic("resource_list_free: resource entry is busy");
                  STAILQ_REMOVE_HEAD(rl, link);
                  free(rle, M_BUS);
          }
  }
  
  /**
   * @brief Add a resource entry.
   *
   * This function adds a resource entry using the given @p type, @p
   * start, @p end and @p count values. A rid value is chosen by
   * searching sequentially for the first unused rid starting at zero.
   *
   * @param rl            the resource list to edit
   * @param type          the resource entry type (e.g. SYS_RES_MEMORY)
   * @param start         the start address of the resource
   * @param end           the end address of the resource
   * @param count         XXX end-start+1
   */
  int
  resource_list_add_next(struct resource_list *rl, int type, rman_res_t start,
      rman_res_t end, rman_res_t count)
  {
          int rid;
  
          rid = 0;
          while (resource_list_find(rl, type, rid) != NULL)
                  rid++;
          resource_list_add(rl, type, rid, start, end, count);
          return (rid);
  }
  
  /**
   * @brief Add or modify a resource entry.
   *
   * If an existing entry exists with the same type and rid, it will be
   * modified using the given values of @p start, @p end and @p
   * count. If no entry exists, a new one will be created using the
   * given values.  The resource list entry that matches is then returned.
   *
   * @param rl            the resource list to edit
   * @param type          the resource entry type (e.g. SYS_RES_MEMORY)
   * @param rid           the resource identifier
   * @param start         the start address of the resource
   * @param end           the end address of the resource
   * @param count         XXX end-start+1
   */
  struct resource_list_entry *
  resource_list_add(struct resource_list *rl, int type, int rid,
      rman_res_t start, rman_res_t end, rman_res_t count)
  {
          struct resource_list_entry *rle;
  
          rle = resource_list_find(rl, type, rid);
          if (!rle) {
                  rle = malloc(sizeof(struct resource_list_entry), M_BUS,
                      M_NOWAIT);
                  if (!rle)
                          panic("resource_list_add: can't record entry");
                  STAILQ_INSERT_TAIL(rl, rle, link);
                  rle->type = type;
                  rle->rid = rid;
                  rle->res = NULL;
                  rle->flags = 0;
          }
  
          if (rle->res)
                  panic("resource_list_add: resource entry is busy");
  
          rle->start = start;
          rle->end = end;
          rle->count = count;
          return (rle);
  }
  
  /**
   * @brief Determine if a resource entry is busy.
   *
   * Returns true if a resource entry is busy meaning that it has an
   * associated resource that is not an unallocated "reserved" resource.
   *
   * @param rl            the resource list to search
   * @param type          the resource entry type (e.g. SYS_RES_MEMORY)
   * @param rid           the resource identifier
   *
   * @returns Non-zero if the entry is busy, zero otherwise.
   */
  int
  resource_list_busy(struct resource_list *rl, int type, int rid)
  {
          struct resource_list_entry *rle;
  
          rle = resource_list_find(rl, type, rid);
          if (rle == NULL || rle->res == NULL)
                  return (0);
          if ((rle->flags & (RLE_RESERVED | RLE_ALLOCATED)) == RLE_RESERVED) {
                  KASSERT(!(rman_get_flags(rle->res) & RF_ACTIVE),
                      ("reserved resource is active"));
                  return (0);
          }
          return (1);
  }
  
  /**
   * @brief Determine if a resource entry is reserved.
   *
   * Returns true if a resource entry is reserved meaning that it has an
   * associated "reserved" resource.  The resource can either be
   * allocated or unallocated.
   *
   * @param rl            the resource list to search
   * @param type          the resource entry type (e.g. SYS_RES_MEMORY)
   * @param rid           the resource identifier
   *
   * @returns Non-zero if the entry is reserved, zero otherwise.
   */
  int
  resource_list_reserved(struct resource_list *rl, int type, int rid)
  {
          struct resource_list_entry *rle;
  
          rle = resource_list_find(rl, type, rid);
          if (rle != NULL && rle->flags & RLE_RESERVED)
                  return (1);
          return (0);
  }
  
  /**
   * @brief Find a resource entry by type and rid.
   *
   * @param rl            the resource list to search
   * @param type          the resource entry type (e.g. SYS_RES_MEMORY)
   * @param rid           the resource identifier
   *
   * @returns the resource entry pointer or NULL if there is no such
   * entry.
   */
  struct resource_list_entry *
  resource_list_find(struct resource_list *rl, int type, int rid)
  {
          struct resource_list_entry *rle;
  
          STAILQ_FOREACH(rle, rl, link) {
                  if (rle->type == type && rle->rid == rid)
                          return (rle);
          }
          return (NULL);
  }
  
  /**
   * @brief Delete a resource entry.
   *
   * @param rl            the resource list to edit
   * @param type          the resource entry type (e.g. SYS_RES_MEMORY)
   * @param rid           the resource identifier
   */
  void
  resource_list_delete(struct resource_list *rl, int type, int rid)
  {
          struct resource_list_entry *rle = resource_list_find(rl, type, rid);
  
          if (rle) {
                  if (rle->res != NULL)
                          panic("resource_list_delete: resource has not been released");
                  STAILQ_REMOVE(rl, rle, resource_list_entry, link);
                  free(rle, M_BUS);
          }
  }
  
  /**
   * @brief Allocate a reserved resource
   *
   * This can be used by buses to force the allocation of resources
   * that are always active in the system even if they are not allocated
   * by a driver (e.g. PCI BARs).  This function is usually called when
   * adding a new child to the bus.  The resource is allocated from the
   * parent bus when it is reserved.  The resource list entry is marked
   * with RLE_RESERVED to note that it is a reserved resource.
   *
   * Subsequent attempts to allocate the resource with
   * resource_list_alloc() will succeed the first time and will set
   * RLE_ALLOCATED to note that it has been allocated.  When a reserved
   * resource that has been allocated is released with
   * resource_list_release() the resource RLE_ALLOCATED is cleared, but
   * the actual resource remains allocated.  The resource can be released to
   * the parent bus by calling resource_list_unreserve().
   *
   * @param rl            the resource list to allocate from
   * @param bus           the parent device of @p child
   * @param child         the device for which the resource is being reserved
   * @param type          the type of resource to allocate
   * @param rid           a pointer to the resource identifier
   * @param start         hint at the start of the resource range - pass
   *                      @c 0 for any start address
   * @param end           hint at the end of the resource range - pass
   *                      @c ~0 for any end address
   * @param count         hint at the size of range required - pass @c 1
   *                      for any size
   * @param flags         any extra flags to control the resource
   *                      allocation - see @c RF_XXX flags in
   *                      <sys/rman.h> for details
   *
   * @returns             the resource which was allocated or @c NULL if no
   *                      resource could be allocated
   */
  struct resource *
  resource_list_reserve(struct resource_list *rl, device_t bus, device_t child,
      int type, int *rid, rman_res_t start, rman_res_t end, rman_res_t count, u_int flags)
  {
          struct resource_list_entry *rle = NULL;
          int passthrough = (device_get_parent(child) != bus);
          struct resource *r;
  
          if (passthrough)
                  panic(
      "resource_list_reserve() should only be called for direct children");
          if (flags & RF_ACTIVE)
                  panic(
      "resource_list_reserve() should only reserve inactive resources");
  
          r = resource_list_alloc(rl, bus, child, type, rid, start, end, count,
              flags);
          if (r != NULL) {
                  rle = resource_list_find(rl, type, *rid);
                  rle->flags |= RLE_RESERVED;
          }
          return (r);
  }
  
  /**
   * @brief Helper function for implementing BUS_ALLOC_RESOURCE()
   *
   * Implement BUS_ALLOC_RESOURCE() by looking up a resource from the list
   * and passing the allocation up to the parent of @p bus. This assumes
   * that the first entry of @c device_get_ivars(child) is a struct
   * resource_list. This also handles 'passthrough' allocations where a
   * child is a remote descendant of bus by passing the allocation up to
   * the parent of bus.
   *
   * Typically, a bus driver would store a list of child resources
   * somewhere in the child device's ivars (see device_get_ivars()) and
   * its implementation of BUS_ALLOC_RESOURCE() would find that list and
   * then call resource_list_alloc() to perform the allocation.
   *
   * @param rl            the resource list to allocate from
   * @param bus           the parent device of @p child
   * @param child         the device which is requesting an allocation
   * @param type          the type of resource to allocate
   * @param rid           a pointer to the resource identifier
   * @param start         hint at the start of the resource range - pass
   *                      @c 0 for any start address
   * @param end           hint at the end of the resource range - pass
   *                      @c ~0 for any end address
   * @param count         hint at the size of range required - pass @c 1
   *                      for any size
   * @param flags         any extra flags to control the resource
   *                      allocation - see @c RF_XXX flags in
   *                      <sys/rman.h> for details
   *
   * @returns             the resource which was allocated or @c NULL if no
   *                      resource could be allocated
   */
  struct resource *
  resource_list_alloc(struct resource_list *rl, device_t bus, device_t child,
      int type, int *rid, rman_res_t start, rman_res_t end, rman_res_t count, u_int flags)
  {
          struct resource_list_entry *rle = NULL;
          int passthrough = (device_get_parent(child) != bus);
          int isdefault = RMAN_IS_DEFAULT_RANGE(start, end);
  
          if (passthrough) {
                  return (BUS_ALLOC_RESOURCE(device_get_parent(bus), child,
                      type, rid, start, end, count, flags));
          }
  
          rle = resource_list_find(rl, type, *rid);
  
          if (!rle)
                  return (NULL);          /* no resource of that type/rid */
  
          if (rle->res) {
                  if (rle->flags & RLE_RESERVED) {
                          if (rle->flags & RLE_ALLOCATED)
                                  return (NULL);
                          if ((flags & RF_ACTIVE) &&
                              bus_activate_resource(child, type, *rid,
                              rle->res) != 0)
                                  return (NULL);
                          rle->flags |= RLE_ALLOCATED;
                          return (rle->res);
                  }
                  device_printf(bus,
                      "resource entry %#x type %d for child %s is busy\n", *rid,
                      type, device_get_nameunit(child));
                  return (NULL);
          }
  
          if (isdefault) {
                  start = rle->start;
                  count = ulmax(count, rle->count);
                  end = ulmax(rle->end, start + count - 1);
          }
  
          rle->res = BUS_ALLOC_RESOURCE(device_get_parent(bus), child,
              type, rid, start, end, count, flags);
  
          /*
           * Record the new range.
           */
          if (rle->res) {
                  rle->start = rman_get_start(rle->res);
                  rle->end = rman_get_end(rle->res);
                  rle->count = count;
          }
  
          return (rle->res);
  }
  
  /**
   * @brief Helper function for implementing BUS_RELEASE_RESOURCE()
   *
   * Implement BUS_RELEASE_RESOURCE() using a resource list. Normally
   * used with resource_list_alloc().
   *
   * @param rl            the resource list which was allocated from
   * @param bus           the parent device of @p child
   * @param child         the device which is requesting a release
   * @param type          the type of resource to release
   * @param rid           the resource identifier
   * @param res           the resource to release
   *
   * @retval 0            success
   * @retval non-zero     a standard unix error code indicating what
   *                      error condition prevented the operation
   */
  int
  resource_list_release(struct resource_list *rl, device_t bus, device_t child,
      int type, int rid, struct resource *res)
  {
          struct resource_list_entry *rle = NULL;
          int passthrough = (device_get_parent(child) != bus);
          int error;
  
          if (passthrough) {
                  return (BUS_RELEASE_RESOURCE(device_get_parent(bus), child,
                      type, rid, res));
          }
  
          rle = resource_list_find(rl, type, rid);
  
          if (!rle)
                  panic("resource_list_release: can't find resource");
          if (!rle->res)
                  panic("resource_list_release: resource entry is not busy");
          if (rle->flags & RLE_RESERVED) {
                  if (rle->flags & RLE_ALLOCATED) {
                          if (rman_get_flags(res) & RF_ACTIVE) {
                                  error = bus_deactivate_resource(child, type,
                                      rid, res);
                                  if (error)
                                          return (error);
                          }
                          rle->flags &= ~RLE_ALLOCATED;
                          return (0);
                  }
                  return (EINVAL);
          }
  
          error = BUS_RELEASE_RESOURCE(device_get_parent(bus), child,
              type, rid, res);
          if (error)
                  return (error);
  
          rle->res = NULL;
          return (0);
  }
  
  /**
   * @brief Release all active resources of a given type
   *
   * Release all active resources of a specified type.  This is intended
   * to be used to cleanup resources leaked by a driver after detach or
   * a failed attach.
   *
   * @param rl            the resource list which was allocated from
   * @param bus           the parent device of @p child
   * @param child         the device whose active resources are being released
   * @param type          the type of resources to release
   *
   * @retval 0            success
   * @retval EBUSY        at least one resource was active
   */
  int
  resource_list_release_active(struct resource_list *rl, device_t bus,
      device_t child, int type)
  {
          struct resource_list_entry *rle;
          int error, retval;
  
          retval = 0;
          STAILQ_FOREACH(rle, rl, link) {
                  if (rle->type != type)
                          continue;
                  if (rle->res == NULL)
                          continue;
                  if ((rle->flags & (RLE_RESERVED | RLE_ALLOCATED)) ==
                      RLE_RESERVED)
                          continue;
                  retval = EBUSY;
                  error = resource_list_release(rl, bus, child, type,
                      rman_get_rid(rle->res), rle->res);
                  if (error != 0)
                          device_printf(bus,
                              "Failed to release active resource: %d\n", error);
          }
          return (retval);
  }
  
  /**
   * @brief Fully release a reserved resource
   *
   * Fully releases a resource reserved via resource_list_reserve().
   *
   * @param rl            the resource list which was allocated from
   * @param bus           the parent device of @p child
   * @param child         the device whose reserved resource is being released
   * @param type          the type of resource to release
   * @param rid           the resource identifier
   * @param res           the resource to release
   *
   * @retval 0            success
   * @retval non-zero     a standard unix error code indicating what
   *                      error condition prevented the operation
   */
  int
  resource_list_unreserve(struct resource_list *rl, device_t bus, device_t child,
      int type, int rid)
  {
          struct resource_list_entry *rle = NULL;
          int passthrough = (device_get_parent(child) != bus);
  
          if (passthrough)
                  panic(
      "resource_list_unreserve() should only be called for direct children");
  
          rle = resource_list_find(rl, type, rid);
  
          if (!rle)
                  panic("resource_list_unreserve: can't find resource");
          if (!(rle->flags & RLE_RESERVED))
                  return (EINVAL);
          if (rle->flags & RLE_ALLOCATED)
                  return (EBUSY);
          rle->flags &= ~RLE_RESERVED;
          return (resource_list_release(rl, bus, child, type, rid, rle->res));
  }
  
  /**
   * @brief Print a description of resources in a resource list
   *
   * Print all resources of a specified type, for use in BUS_PRINT_CHILD().
   * The name is printed if at least one resource of the given type is available.
   * The format is used to print resource start and end.
   *
   * @param rl            the resource list to print
   * @param name          the name of @p type, e.g. @c "memory"
   * @param type          type type of resource entry to print
   * @param format        printf(9) format string to print resource
   *                      start and end values
   *
   * @returns             the number of characters printed
   */
  int
  resource_list_print_type(struct resource_list *rl, const char *name, int type,
      const char *format)
  {
          struct resource_list_entry *rle;
          int printed, retval;
  
          printed = 0;
          retval = 0;
          /* Yes, this is kinda cheating */
          STAILQ_FOREACH(rle, rl, link) {
                  if (rle->type == type) {
                          if (printed == 0)
                                  retval += printf(" %s ", name);
                          else
                                  retval += printf(",");
                          printed++;
                          retval += printf(format, rle->start);
                          if (rle->count > 1) {
                                  retval += printf("-");
                                  retval += printf(format, rle->start +
                                                   rle->count - 1);
                          }
                  }
          }
          return (retval);
  }
  
  /**
   * @brief Releases all the resources in a list.
   *
   * @param rl            The resource list to purge.
   *
   * @returns             nothing
   */
  void
  resource_list_purge(struct resource_list *rl)
  {
          struct resource_list_entry *rle;
  
          while ((rle = STAILQ_FIRST(rl)) != NULL) {
                  if (rle->res)
                          bus_release_resource(rman_get_device(rle->res),
                              rle->type, rle->rid, rle->res);
                  STAILQ_REMOVE_HEAD(rl, link);
                  free(rle, M_BUS);
          }
  }
  
  device_t
  bus_generic_add_child(device_t dev, u_int order, const char *name, int unit)
  {
          return (device_add_child_ordered(dev, order, name, unit));
  }
  
  /**
   * @brief Helper function for implementing DEVICE_PROBE()
   *
   * This function can be used to help implement the DEVICE_PROBE() for
   * a bus (i.e. a device which has other devices attached to it). It
   * calls the DEVICE_IDENTIFY() method of each driver in the device's
   * devclass.
   */
  int
  bus_generic_probe(device_t dev)
  {
          devclass_t dc = dev->devclass;
          driverlink_t dl;
  
          TAILQ_FOREACH(dl, &dc->drivers, link) {
                  /*
                   * If this driver's pass is too high, then ignore it.
                   * For most drivers in the default pass, this will
                   * never be true.  For early-pass drivers they will
                   * only call the identify routines of eligible drivers
                   * when this routine is called.  Drivers for later
                   * passes should have their identify routines called
                   * on early-pass buses during BUS_NEW_PASS().
                   */
                  if (dl->pass > bus_current_pass)
                          continue;
                  DEVICE_IDENTIFY(dl->driver, dev);
          }
  
          return (0);
  }
  
  /**
   * @brief Helper function for implementing DEVICE_ATTACH()
   *
   * This function can be used to help implement the DEVICE_ATTACH() for
   * a bus. It calls device_probe_and_attach() for each of the device's
   * children.
   */
  int
  bus_generic_attach(device_t dev)
  {
          device_t child;
  
          TAILQ_FOREACH(child, &dev->children, link) {
                  device_probe_and_attach(child);
          }
  
          return (0);
  }
  
  /**
   * @brief Helper function for delaying attaching children
   *
   * Many buses can't run transactions on the bus which children need to probe and
   * attach until after interrupts and/or timers are running.  This function
   * delays their attach until interrupts and timers are enabled.
   */
  int
  bus_delayed_attach_children(device_t dev)
  {
          /* Probe and attach the bus children when interrupts are available */
          config_intrhook_oneshot((ich_func_t)bus_generic_attach, dev);
  
          return (0);
  }
  
  /**
   * @brief Helper function for implementing DEVICE_DETACH()
   *
   * This function can be used to help implement the DEVICE_DETACH() for
   * a bus. It calls device_detach() for each of the device's
   * children.
   */
  int
  bus_generic_detach(device_t dev)
  {
          device_t child;
          int error;
  
          if (dev->state != DS_ATTACHED)
                  return (EBUSY);
  
          /*
           * Detach children in the reverse order.
           * See bus_generic_suspend for details.
           */
          TAILQ_FOREACH_REVERSE(child, &dev->children, device_list, link) {
                  if ((error = device_detach(child)) != 0)
                          return (error);
          }
  
          return (0);
  }
  
  /**
   * @brief Helper function for implementing DEVICE_SHUTDOWN()
   *
   * This function can be used to help implement the DEVICE_SHUTDOWN()
   * for a bus. It calls device_shutdown() for each of the device's
   * children.
   */
  int
  bus_generic_shutdown(device_t dev)
  {
          device_t child;
  
          /*
           * Shut down children in the reverse order.
           * See bus_generic_suspend for details.
           */
          TAILQ_FOREACH_REVERSE(child, &dev->children, device_list, link) {
                  device_shutdown(child);
          }
  
          return (0);
  }
  
  /**
   * @brief Default function for suspending a child device.
   *
   * This function is to be used by a bus's DEVICE_SUSPEND_CHILD().
   */
  int
  bus_generic_suspend_child(device_t dev, device_t child)
  {
          int     error;
  
          error = DEVICE_SUSPEND(child);
  
          if (error == 0)
                  child->flags |= DF_SUSPENDED;
  
          return (error);
  }
  
  /**
   * @brief Default function for resuming a child device.
   *
   * This function is to be used by a bus's DEVICE_RESUME_CHILD().
   */
  int
  bus_generic_resume_child(device_t dev, device_t child)
  {
          DEVICE_RESUME(child);
          child->flags &= ~DF_SUSPENDED;
  
          return (0);
  }
  
  /**
   * @brief Helper function for implementing DEVICE_SUSPEND()
   *
   * This function can be used to help implement the DEVICE_SUSPEND()
   * for a bus. It calls DEVICE_SUSPEND() for each of the device's
   * children. If any call to DEVICE_SUSPEND() fails, the suspend
   * operation is aborted and any devices which were suspended are
   * resumed immediately by calling their DEVICE_RESUME() methods.
   */
  int
  bus_generic_suspend(device_t dev)
  {
          int             error;
          device_t        child;
  
          /*
           * Suspend children in the reverse order.
           * For most buses all children are equal, so the order does not matter.
           * Other buses, such as acpi, carefully order their child devices to
           * express implicit dependencies between them.  For such buses it is
           * safer to bring down devices in the reverse order.
           */
          TAILQ_FOREACH_REVERSE(child, &dev->children, device_list, link) {
                  error = BUS_SUSPEND_CHILD(dev, child);
                  if (error != 0) {
                          child = TAILQ_NEXT(child, link);
                          if (child != NULL) {
                                  TAILQ_FOREACH_FROM(child, &dev->children, link)
                                          BUS_RESUME_CHILD(dev, child);
                          }
                          return (error);
                  }
          }
          return (0);
  }
  
  /**
   * @brief Helper function for implementing DEVICE_RESUME()
   *
   * This function can be used to help implement the DEVICE_RESUME() for
   * a bus. It calls DEVICE_RESUME() on each of the device's children.
   */
  int
  bus_generic_resume(device_t dev)
  {
          device_t        child;
  
          TAILQ_FOREACH(child, &dev->children, link) {
                  BUS_RESUME_CHILD(dev, child);
                  /* if resume fails, there's nothing we can usefully do... */
          }
          return (0);
  }
  
  /**
   * @brief Helper function for implementing BUS_RESET_POST
   *
   * Bus can use this function to implement common operations of
   * re-attaching or resuming the children after the bus itself was
   * reset, and after restoring bus-unique state of children.
   *
   * @param dev   The bus
   * #param flags DEVF_RESET_*
   */
  int
  bus_helper_reset_post(device_t dev, int flags)
  {
          device_t child;
          int error, error1;
  
          error = 0;
          TAILQ_FOREACH(child, &dev->children,link) {
                  BUS_RESET_POST(dev, child);
                  error1 = (flags & DEVF_RESET_DETACH) != 0 ?
                      device_probe_and_attach(child) :
                      BUS_RESUME_CHILD(dev, child);
                  if (error == 0 && error1 != 0)
                          error = error1;
          }
          return (error);
  }
  
  static void
  bus_helper_reset_prepare_rollback(device_t dev, device_t child, int flags)
  {
          child = TAILQ_NEXT(child, link);
          if (child == NULL)
                  return;
          TAILQ_FOREACH_FROM(child, &dev->children,link) {
                  BUS_RESET_POST(dev, child);
                  if ((flags & DEVF_RESET_DETACH) != 0)
                          device_probe_and_attach(child);
                  else
                          BUS_RESUME_CHILD(dev, child);
          }
  }
  
  /**
   * @brief Helper function for implementing BUS_RESET_PREPARE
   *
   * Bus can use this function to implement common operations of
   * detaching or suspending the children before the bus itself is
   * reset, and then save bus-unique state of children that must
   * persists around reset.
   *
   * @param dev   The bus
   * #param flags DEVF_RESET_*
   */
  int
  bus_helper_reset_prepare(device_t dev, int flags)
  {
          device_t child;
          int error;
  
          if (dev->state != DS_ATTACHED)
                  return (EBUSY);
  
          TAILQ_FOREACH_REVERSE(child, &dev->children, device_list, link) {
                  if ((flags & DEVF_RESET_DETACH) != 0) {
                          error = device_get_state(child) == DS_ATTACHED ?
                              device_detach(child) : 0;
                  } else {
                          error = BUS_SUSPEND_CHILD(dev, child);
                  }
                  if (error == 0) {
                          error = BUS_RESET_PREPARE(dev, child);
                          if (error != 0) {
                                  if ((flags & DEVF_RESET_DETACH) != 0)
                                          device_probe_and_attach(child);
                                  else
                                          BUS_RESUME_CHILD(dev, child);
                          }
                  }
                  if (error != 0) {
                          bus_helper_reset_prepare_rollback(dev, child, flags);
                          return (error);
                  }
          }
          return (0);
  }
  
  /**
   * @brief Helper function for implementing BUS_PRINT_CHILD().
   *
   * This function prints the first part of the ascii representation of
   * @p child, including its name, unit and description (if any - see
   * device_set_desc()).
   *
   * @returns the number of characters printed
   */
  int
  bus_print_child_header(device_t dev, device_t child)
  {
          int     retval = 0;
  
          if (device_get_desc(child)) {
                  retval += device_printf(child, "<%s>", device_get_desc(child));
          } else {
                  retval += printf("%s", device_get_nameunit(child));
          }
  
          return (retval);
  }
  
  /**
   * @brief Helper function for implementing BUS_PRINT_CHILD().
   *
   * This function prints the last part of the ascii representation of
   * @p child, which consists of the string @c " on " followed by the
   * name and unit of the @p dev.
   *
   * @returns the number of characters printed
   */
  int
  bus_print_child_footer(device_t dev, device_t child)
  {
          return (printf(" on %s\n", device_get_nameunit(dev)));
  }
  
  /**
   * @brief Helper function for implementing BUS_PRINT_CHILD().
   *
   * This function prints out the VM domain for the given device.
   *
   * @returns the number of characters printed
   */
  int
  bus_print_child_domain(device_t dev, device_t child)
  {
          int domain;
  
          /* No domain? Don't print anything */
          if (BUS_GET_DOMAIN(dev, child, &domain) != 0)
                  return (0);
  
          return (printf(" numa-domain %d", domain));
  }
  
  /**
   * @brief Helper function for implementing BUS_PRINT_CHILD().
   *
   * This function simply calls bus_print_child_header() followed by
   * bus_print_child_footer().
   *
   * @returns the number of characters printed
   */
  int
  bus_generic_print_child(device_t dev, device_t child)
  {
          int     retval = 0;
  
          retval += bus_print_child_header(dev, child);
          retval += bus_print_child_domain(dev, child);
          retval += bus_print_child_footer(dev, child);
  
          return (retval);
  }
  
  /**
   * @brief Stub function for implementing BUS_READ_IVAR().
   *
   * @returns ENOENT
   */
  int
  bus_generic_read_ivar(device_t dev, device_t child, int index,
      uintptr_t * result)
  {
          return (ENOENT);
  }
  
  /**
   * @brief Stub function for implementing BUS_WRITE_IVAR().
   *
   * @returns ENOENT
   */
  int
  bus_generic_write_ivar(device_t dev, device_t child, int index,
      uintptr_t value)
  {
          return (ENOENT);
  }
  
  /**
   * @brief Helper function for implementing BUS_GET_PROPERTY().
   *
   * This simply calls the BUS_GET_PROPERTY of the parent of dev,
   * until a non-default implementation is found.
   */
  ssize_t
  bus_generic_get_property(device_t dev, device_t child, const char *propname,
      void *propvalue, size_t size, device_property_type_t type)
  {
          if (device_get_parent(dev) != NULL)
                  return (BUS_GET_PROPERTY(device_get_parent(dev), child,
                      propname, propvalue, size, type));
  
          return (-1);
  }
  
  /**
   * @brief Stub function for implementing BUS_GET_RESOURCE_LIST().
   *
   * @returns NULL
   */
  struct resource_list *
  bus_generic_get_resource_list(device_t dev, device_t child)
  {
          return (NULL);
  }
  
  /**
   * @brief Helper function for implementing BUS_DRIVER_ADDED().
   *
   * This implementation of BUS_DRIVER_ADDED() simply calls the driver's
   * DEVICE_IDENTIFY() method to allow it to add new children to the bus
   * and then calls device_probe_and_attach() for each unattached child.
   */
  void
  bus_generic_driver_added(device_t dev, driver_t *driver)
  {
          device_t child;
  
          DEVICE_IDENTIFY(driver, dev);
          TAILQ_FOREACH(child, &dev->children, link) {
                  if (child->state == DS_NOTPRESENT)
                          device_probe_and_attach(child);
          }
  }
  
  /**
   * @brief Helper function for implementing BUS_NEW_PASS().
   *
   * This implementing of BUS_NEW_PASS() first calls the identify
   * routines for any drivers that probe at the current pass.  Then it
   * walks the list of devices for this bus.  If a device is already
   * attached, then it calls BUS_NEW_PASS() on that device.  If the
   * device is not already attached, it attempts to attach a driver to
   * it.
   */
  void
  bus_generic_new_pass(device_t dev)
  {
          driverlink_t dl;
          devclass_t dc;
          device_t child;
  
          dc = dev->devclass;
          TAILQ_FOREACH(dl, &dc->drivers, link) {
                  if (dl->pass == bus_current_pass)
                          DEVICE_IDENTIFY(dl->driver, dev);
          }
          TAILQ_FOREACH(child, &dev->children, link) {
                  if (child->state >= DS_ATTACHED)
                          BUS_NEW_PASS(child);
                  else if (child->state == DS_NOTPRESENT)
                          device_probe_and_attach(child);
          }
  }
  
  /**
   * @brief Helper function for implementing BUS_SETUP_INTR().
   *
   * This simple implementation of BUS_SETUP_INTR() simply calls the
   * BUS_SETUP_INTR() method of the parent of @p dev.
   */
  int
  bus_generic_setup_intr(device_t dev, device_t child, struct resource *irq,
      int flags, driver_filter_t *filter, driver_intr_t *intr, void *arg,
      void **cookiep)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_SETUP_INTR(dev->parent, child, irq, flags,
                      filter, intr, arg, cookiep));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_TEARDOWN_INTR().
   *
   * This simple implementation of BUS_TEARDOWN_INTR() simply calls the
   * BUS_TEARDOWN_INTR() method of the parent of @p dev.
   */
  int
  bus_generic_teardown_intr(device_t dev, device_t child, struct resource *irq,
      void *cookie)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_TEARDOWN_INTR(dev->parent, child, irq, cookie));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_SUSPEND_INTR().
   *
   * This simple implementation of BUS_SUSPEND_INTR() simply calls the
   * BUS_SUSPEND_INTR() method of the parent of @p dev.
   */
  int
  bus_generic_suspend_intr(device_t dev, device_t child, struct resource *irq)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_SUSPEND_INTR(dev->parent, child, irq));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_RESUME_INTR().
   *
   * This simple implementation of BUS_RESUME_INTR() simply calls the
   * BUS_RESUME_INTR() method of the parent of @p dev.
   */
  int
  bus_generic_resume_intr(device_t dev, device_t child, struct resource *irq)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_RESUME_INTR(dev->parent, child, irq));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_ADJUST_RESOURCE().
   *
   * This simple implementation of BUS_ADJUST_RESOURCE() simply calls the
   * BUS_ADJUST_RESOURCE() method of the parent of @p dev.
   */
  int
  bus_generic_adjust_resource(device_t dev, device_t child, int type,
      struct resource *r, rman_res_t start, rman_res_t end)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_ADJUST_RESOURCE(dev->parent, child, type, r, start,
                      end));
          return (EINVAL);
  }
  
  /*
   * @brief Helper function for implementing BUS_TRANSLATE_RESOURCE().
   *
   * This simple implementation of BUS_TRANSLATE_RESOURCE() simply calls the
   * BUS_TRANSLATE_RESOURCE() method of the parent of @p dev.  If there is no
   * parent, no translation happens.
   */
  int
  bus_generic_translate_resource(device_t dev, int type, rman_res_t start,
      rman_res_t *newstart)
  {
          if (dev->parent)
                  return (BUS_TRANSLATE_RESOURCE(dev->parent, type, start,
                      newstart));
          *newstart = start;
          return (0);
  }
  
  /**
   * @brief Helper function for implementing BUS_ALLOC_RESOURCE().
   *
   * This simple implementation of BUS_ALLOC_RESOURCE() simply calls the
   * BUS_ALLOC_RESOURCE() method of the parent of @p dev.
   */
  struct resource *
  bus_generic_alloc_resource(device_t dev, device_t child, int type, int *rid,
      rman_res_t start, rman_res_t end, rman_res_t count, u_int flags)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_ALLOC_RESOURCE(dev->parent, child, type, rid,
                      start, end, count, flags));
          return (NULL);
  }
  
  /**
   * @brief Helper function for implementing BUS_RELEASE_RESOURCE().
   *
   * This simple implementation of BUS_RELEASE_RESOURCE() simply calls the
   * BUS_RELEASE_RESOURCE() method of the parent of @p dev.
   */
  int
  bus_generic_release_resource(device_t dev, device_t child, int type, int rid,
      struct resource *r)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_RELEASE_RESOURCE(dev->parent, child, type, rid,
                      r));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_ACTIVATE_RESOURCE().
   *
   * This simple implementation of BUS_ACTIVATE_RESOURCE() simply calls the
   * BUS_ACTIVATE_RESOURCE() method of the parent of @p dev.
   */
  int
  bus_generic_activate_resource(device_t dev, device_t child, int type, int rid,
      struct resource *r)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_ACTIVATE_RESOURCE(dev->parent, child, type, rid,
                      r));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_DEACTIVATE_RESOURCE().
   *
   * This simple implementation of BUS_DEACTIVATE_RESOURCE() simply calls the
   * BUS_DEACTIVATE_RESOURCE() method of the parent of @p dev.
   */
  int
  bus_generic_deactivate_resource(device_t dev, device_t child, int type,
      int rid, struct resource *r)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_DEACTIVATE_RESOURCE(dev->parent, child, type, rid,
                      r));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_MAP_RESOURCE().
   *
   * This simple implementation of BUS_MAP_RESOURCE() simply calls the
   * BUS_MAP_RESOURCE() method of the parent of @p dev.
   */
  int
  bus_generic_map_resource(device_t dev, device_t child, int type,
      struct resource *r, struct resource_map_request *args,
      struct resource_map *map)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_MAP_RESOURCE(dev->parent, child, type, r, args,
                      map));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_UNMAP_RESOURCE().
   *
   * This simple implementation of BUS_UNMAP_RESOURCE() simply calls the
   * BUS_UNMAP_RESOURCE() method of the parent of @p dev.
   */
  int
  bus_generic_unmap_resource(device_t dev, device_t child, int type,
      struct resource *r, struct resource_map *map)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_UNMAP_RESOURCE(dev->parent, child, type, r, map));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_BIND_INTR().
   *
   * This simple implementation of BUS_BIND_INTR() simply calls the
   * BUS_BIND_INTR() method of the parent of @p dev.
   */
  int
  bus_generic_bind_intr(device_t dev, device_t child, struct resource *irq,
      int cpu)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_BIND_INTR(dev->parent, child, irq, cpu));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_CONFIG_INTR().
   *
   * This simple implementation of BUS_CONFIG_INTR() simply calls the
   * BUS_CONFIG_INTR() method of the parent of @p dev.
   */
  int
  bus_generic_config_intr(device_t dev, int irq, enum intr_trigger trig,
      enum intr_polarity pol)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_CONFIG_INTR(dev->parent, irq, trig, pol));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_DESCRIBE_INTR().
   *
   * This simple implementation of BUS_DESCRIBE_INTR() simply calls the
   * BUS_DESCRIBE_INTR() method of the parent of @p dev.
   */
  int
  bus_generic_describe_intr(device_t dev, device_t child, struct resource *irq,
      void *cookie, const char *descr)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent)
                  return (BUS_DESCRIBE_INTR(dev->parent, child, irq, cookie,
                      descr));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_GET_CPUS().
   *
   * This simple implementation of BUS_GET_CPUS() simply calls the
   * BUS_GET_CPUS() method of the parent of @p dev.
   */
  int
  bus_generic_get_cpus(device_t dev, device_t child, enum cpu_sets op,
      size_t setsize, cpuset_t *cpuset)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent != NULL)
                  return (BUS_GET_CPUS(dev->parent, child, op, setsize, cpuset));
          return (EINVAL);
  }
  
  /**
   * @brief Helper function for implementing BUS_GET_DMA_TAG().
   *
   * This simple implementation of BUS_GET_DMA_TAG() simply calls the
   * BUS_GET_DMA_TAG() method of the parent of @p dev.
   */
  bus_dma_tag_t
  bus_generic_get_dma_tag(device_t dev, device_t child)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent != NULL)
                  return (BUS_GET_DMA_TAG(dev->parent, child));
          return (NULL);
  }
  
  /**
   * @brief Helper function for implementing BUS_GET_BUS_TAG().
   *
   * This simple implementation of BUS_GET_BUS_TAG() simply calls the
   * BUS_GET_BUS_TAG() method of the parent of @p dev.
   */
  bus_space_tag_t
  bus_generic_get_bus_tag(device_t dev, device_t child)
  {
          /* Propagate up the bus hierarchy until someone handles it. */
          if (dev->parent != NULL)
                  return (BUS_GET_BUS_TAG(dev->parent, child));
          return ((bus_space_tag_t)0);
  }
  
  /**
   * @brief Helper function for implementing BUS_GET_RESOURCE().
   *
   * This implementation of BUS_GET_RESOURCE() uses the
   * resource_list_find() function to do most of the work. It calls
   * BUS_GET_RESOURCE_LIST() to find a suitable resource list to
   * search.
   */
  int
  bus_generic_rl_get_resource(device_t dev, device_t child, int type, int rid,
      rman_res_t *startp, rman_res_t *countp)
  {
          struct resource_list *          rl = NULL;
          struct resource_list_entry *    rle = NULL;
  
          rl = BUS_GET_RESOURCE_LIST(dev, child);
          if (!rl)
                  return (EINVAL);
  
          rle = resource_list_find(rl, type, rid);
          if (!rle)
                  return (ENOENT);
  
          if (startp)
                  *startp = rle->start;
          if (countp)
                  *countp = rle->count;
  
          return (0);
  }
  
  /**
   * @brief Helper function for implementing BUS_SET_RESOURCE().
   *
   * This implementation of BUS_SET_RESOURCE() uses the
   * resource_list_add() function to do most of the work. It calls
   * BUS_GET_RESOURCE_LIST() to find a suitable resource list to
   * edit.
   */
  int
  bus_generic_rl_set_resource(device_t dev, device_t child, int type, int rid,
      rman_res_t start, rman_res_t count)
  {
          struct resource_list *          rl = NULL;
  
          rl = BUS_GET_RESOURCE_LIST(dev, child);
          if (!rl)
                  return (EINVAL);
  
          resource_list_add(rl, type, rid, start, (start + count - 1), count);
  
          return (0);
  }
  
  /**
   * @brief Helper function for implementing BUS_DELETE_RESOURCE().
   *
   * This implementation of BUS_DELETE_RESOURCE() uses the
   * resource_list_delete() function to do most of the work. It calls
   * BUS_GET_RESOURCE_LIST() to find a suitable resource list to
   * edit.
   */
  void
  bus_generic_rl_delete_resource(device_t dev, device_t child, int type, int rid)
  {
          struct resource_list *          rl = NULL;
  
          rl = BUS_GET_RESOURCE_LIST(dev, child);
          if (!rl)
                  return;
  
          resource_list_delete(rl, type, rid);
  
          return;
  }
  
  /**
   * @brief Helper function for implementing BUS_RELEASE_RESOURCE().
   *
   * This implementation of BUS_RELEASE_RESOURCE() uses the
   * resource_list_release() function to do most of the work. It calls
   * BUS_GET_RESOURCE_LIST() to find a suitable resource list.
   */
  int
  bus_generic_rl_release_resource(device_t dev, device_t child, int type,
      int rid, struct resource *r)
  {
          struct resource_list *          rl = NULL;
  
          if (device_get_parent(child) != dev)
                  return (BUS_RELEASE_RESOURCE(device_get_parent(dev), child,
                      type, rid, r));
  
          rl = BUS_GET_RESOURCE_LIST(dev, child);
          if (!rl)
                  return (EINVAL);
  
          return (resource_list_release(rl, dev, child, type, rid, r));
  }
  
  /**
   * @brief Helper function for implementing BUS_ALLOC_RESOURCE().
   *
   * This implementation of BUS_ALLOC_RESOURCE() uses the
   * resource_list_alloc() function to do most of the work. It calls
   * BUS_GET_RESOURCE_LIST() to find a suitable resource list.
   */
  struct resource *
  bus_generic_rl_alloc_resource(device_t dev, device_t child, int type,
      int *rid, rman_res_t start, rman_res_t end, rman_res_t count, u_int flags)
  {
          struct resource_list *          rl = NULL;
  
          if (device_get_parent(child) != dev)
                  return (BUS_ALLOC_RESOURCE(device_get_parent(dev), child,
                      type, rid, start, end, count, flags));
  
          rl = BUS_GET_RESOURCE_LIST(dev, child);
          if (!rl)
                  return (NULL);
  
          return (resource_list_alloc(rl, dev, child, type, rid,
              start, end, count, flags));
  }
  
  /**
   * @brief Helper function for implementing BUS_CHILD_PRESENT().
   *
   * This simple implementation of BUS_CHILD_PRESENT() simply calls the
   * BUS_CHILD_PRESENT() method of the parent of @p dev.
   */
  int
  bus_generic_child_present(device_t dev, device_t child)
  {
          return (BUS_CHILD_PRESENT(device_get_parent(dev), dev));
  }
  
  int
  bus_generic_get_domain(device_t dev, device_t child, int *domain)
  {
          if (dev->parent)
                  return (BUS_GET_DOMAIN(dev->parent, dev, domain));
  
          return (ENOENT);
  }
  
  /**
   * @brief Helper function to implement normal BUS_GET_DEVICE_PATH()
   *
   * This function knows how to (a) pass the request up the tree if there's
   * a parent and (b) Knows how to supply a FreeBSD locator.
   *
   * @param bus           bus in the walk up the tree
   * @param child         leaf node to print information about
   * @param locator       BUS_LOCATOR_xxx string for locator
   * @param sb            Buffer to print information into
   */
  int
  bus_generic_get_device_path(device_t bus, device_t child, const char *locator,
      struct sbuf *sb)
  {
          int rv = 0;
          device_t parent;
  
          /*
           * We don't recurse on ACPI since either we know the handle for the
           * device or we don't. And if we're in the generic routine, we don't
           * have a ACPI override. All other locators build up a path by having
           * their parents create a path and then adding the path element for this
           * node. That's why we recurse with parent, bus rather than the typical
           * parent, child: each spot in the tree is independent of what our child
           * will do with this path.
           */
          parent = device_get_parent(bus);
          if (parent != NULL && strcmp(locator, BUS_LOCATOR_ACPI) != 0) {
                  rv = BUS_GET_DEVICE_PATH(parent, bus, locator, sb);
          }
          if (strcmp(locator, BUS_LOCATOR_FREEBSD) == 0) {
                  if (rv == 0) {
                          sbuf_printf(sb, "/%s", device_get_nameunit(child));
                  }
                  return (rv);
          }
          /*
           * Don't know what to do. So assume we do nothing. Not sure that's
           * the right thing, but keeps us from having a big list here.
           */
          return (0);
  }
  
  
  /**
   * @brief Helper function for implementing BUS_RESCAN().
   *
   * This null implementation of BUS_RESCAN() always fails to indicate
   * the bus does not support rescanning.
   */
  int
  bus_null_rescan(device_t dev)
  {
          return (ENODEV);
  }
  
  /*
   * Some convenience functions to make it easier for drivers to use the
   * resource-management functions.  All these really do is hide the
   * indirection through the parent's method table, making for slightly
   * less-wordy code.  In the future, it might make sense for this code
   * to maintain some sort of a list of resources allocated by each device.
   */
  
  int
  bus_alloc_resources(device_t dev, struct resource_spec *rs,
      struct resource **res)
  {
          int i;
  
          for (i = 0; rs[i].type != -1; i++)
                  res[i] = NULL;
          for (i = 0; rs[i].type != -1; i++) {
                  res[i] = bus_alloc_resource_any(dev,
                      rs[i].type, &rs[i].rid, rs[i].flags);
                  if (res[i] == NULL && !(rs[i].flags & RF_OPTIONAL)) {
                          bus_release_resources(dev, rs, res);
                          return (ENXIO);
                  }
          }
          return (0);
  }
  
  void
  bus_release_resources(device_t dev, const struct resource_spec *rs,
      struct resource **res)
  {
          int i;
  
          for (i = 0; rs[i].type != -1; i++)
                  if (res[i] != NULL) {
                          bus_release_resource(
                              dev, rs[i].type, rs[i].rid, res[i]);
                          res[i] = NULL;
                  }
  }
  
  /**
   * @brief Wrapper function for BUS_ALLOC_RESOURCE().
   *
   * This function simply calls the BUS_ALLOC_RESOURCE() method of the
   * parent of @p dev.
   */
  struct resource *
  bus_alloc_resource(device_t dev, int type, int *rid, rman_res_t start,
      rman_res_t end, rman_res_t count, u_int flags)
  {
          struct resource *res;
  
          if (dev->parent == NULL)
                  return (NULL);
          res = BUS_ALLOC_RESOURCE(dev->parent, dev, type, rid, start, end,
              count, flags);
          return (res);
  }
  
  /**
   * @brief Wrapper function for BUS_ADJUST_RESOURCE().
   *
   * This function simply calls the BUS_ADJUST_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_adjust_resource(device_t dev, int type, struct resource *r, rman_res_t start,
      rman_res_t end)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_ADJUST_RESOURCE(dev->parent, dev, type, r, start, end));
  }
  
  /**
   * @brief Wrapper function for BUS_TRANSLATE_RESOURCE().
   *
   * This function simply calls the BUS_TRANSLATE_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_translate_resource(device_t dev, int type, rman_res_t start,
      rman_res_t *newstart)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_TRANSLATE_RESOURCE(dev->parent, type, start, newstart));
  }
  
  /**
   * @brief Wrapper function for BUS_ACTIVATE_RESOURCE().
   *
   * This function simply calls the BUS_ACTIVATE_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_activate_resource(device_t dev, int type, int rid, struct resource *r)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_ACTIVATE_RESOURCE(dev->parent, dev, type, rid, r));
  }
  
  /**
   * @brief Wrapper function for BUS_DEACTIVATE_RESOURCE().
   *
   * This function simply calls the BUS_DEACTIVATE_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_deactivate_resource(device_t dev, int type, int rid, struct resource *r)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_DEACTIVATE_RESOURCE(dev->parent, dev, type, rid, r));
  }
  
  /**
   * @brief Wrapper function for BUS_MAP_RESOURCE().
   *
   * This function simply calls the BUS_MAP_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_map_resource(device_t dev, int type, struct resource *r,
      struct resource_map_request *args, struct resource_map *map)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_MAP_RESOURCE(dev->parent, dev, type, r, args, map));
  }
  
  /**
   * @brief Wrapper function for BUS_UNMAP_RESOURCE().
   *
   * This function simply calls the BUS_UNMAP_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_unmap_resource(device_t dev, int type, struct resource *r,
      struct resource_map *map)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_UNMAP_RESOURCE(dev->parent, dev, type, r, map));
  }
  
  /**
   * @brief Wrapper function for BUS_RELEASE_RESOURCE().
   *
   * This function simply calls the BUS_RELEASE_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_release_resource(device_t dev, int type, int rid, struct resource *r)
  {
          int rv;
  
          if (dev->parent == NULL)
                  return (EINVAL);
          rv = BUS_RELEASE_RESOURCE(dev->parent, dev, type, rid, r);
          return (rv);
  }
  
  /**
   * @brief Wrapper function for BUS_SETUP_INTR().
   *
   * This function simply calls the BUS_SETUP_INTR() method of the
   * parent of @p dev.
   */
  int
  bus_setup_intr(device_t dev, struct resource *r, int flags,
      driver_filter_t filter, driver_intr_t handler, void *arg, void **cookiep)
  {
          int error;
  
          if (dev->parent == NULL)
                  return (EINVAL);
          error = BUS_SETUP_INTR(dev->parent, dev, r, flags, filter, handler,
              arg, cookiep);
          if (error != 0)
                  return (error);
          if (handler != NULL && !(flags & INTR_MPSAFE))
                  device_printf(dev, "[GIANT-LOCKED]\n");
          return (0);
  }
  
  /**
   * @brief Wrapper function for BUS_TEARDOWN_INTR().
   *
   * This function simply calls the BUS_TEARDOWN_INTR() method of the
   * parent of @p dev.
   */
  int
  bus_teardown_intr(device_t dev, struct resource *r, void *cookie)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_TEARDOWN_INTR(dev->parent, dev, r, cookie));
  }
  
  /**
   * @brief Wrapper function for BUS_SUSPEND_INTR().
   *
   * This function simply calls the BUS_SUSPEND_INTR() method of the
   * parent of @p dev.
   */
  int
  bus_suspend_intr(device_t dev, struct resource *r)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_SUSPEND_INTR(dev->parent, dev, r));
  }
  
  /**
   * @brief Wrapper function for BUS_RESUME_INTR().
   *
   * This function simply calls the BUS_RESUME_INTR() method of the
   * parent of @p dev.
   */
  int
  bus_resume_intr(device_t dev, struct resource *r)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_RESUME_INTR(dev->parent, dev, r));
  }
  
  /**
   * @brief Wrapper function for BUS_BIND_INTR().
   *
   * This function simply calls the BUS_BIND_INTR() method of the
   * parent of @p dev.
   */
  int
  bus_bind_intr(device_t dev, struct resource *r, int cpu)
  {
          if (dev->parent == NULL)
                  return (EINVAL);
          return (BUS_BIND_INTR(dev->parent, dev, r, cpu));
  }
  
  /**
   * @brief Wrapper function for BUS_DESCRIBE_INTR().
   *
   * This function first formats the requested description into a
   * temporary buffer and then calls the BUS_DESCRIBE_INTR() method of
   * the parent of @p dev.
   */
  int
  bus_describe_intr(device_t dev, struct resource *irq, void *cookie,
      const char *fmt, ...)
  {
          va_list ap;
          char descr[MAXCOMLEN + 1];
  
          if (dev->parent == NULL)
                  return (EINVAL);
          va_start(ap, fmt);
          vsnprintf(descr, sizeof(descr), fmt, ap);
          va_end(ap);
          return (BUS_DESCRIBE_INTR(dev->parent, dev, irq, cookie, descr));
  }
  
  /**
   * @brief Wrapper function for BUS_SET_RESOURCE().
   *
   * This function simply calls the BUS_SET_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_set_resource(device_t dev, int type, int rid,
      rman_res_t start, rman_res_t count)
  {
          return (BUS_SET_RESOURCE(device_get_parent(dev), dev, type, rid,
              start, count));
  }
  
  /**
   * @brief Wrapper function for BUS_GET_RESOURCE().
   *
   * This function simply calls the BUS_GET_RESOURCE() method of the
   * parent of @p dev.
   */
  int
  bus_get_resource(device_t dev, int type, int rid,
      rman_res_t *startp, rman_res_t *countp)
  {
          return (BUS_GET_RESOURCE(device_get_parent(dev), dev, type, rid,
              startp, countp));
  }
  
  /**
   * @brief Wrapper function for BUS_GET_RESOURCE().
   *
   * This function simply calls the BUS_GET_RESOURCE() method of the
   * parent of @p dev and returns the start value.
   */
  rman_res_t
  bus_get_resource_start(device_t dev, int type, int rid)
  {
          rman_res_t start;
          rman_res_t count;
          int error;
  
          error = BUS_GET_RESOURCE(device_get_parent(dev), dev, type, rid,
              &start, &count);
          if (error)
                  return (0);
          return (start);
  }
  
  /**
   * @brief Wrapper function for BUS_GET_RESOURCE().
   *
   * This function simply calls the BUS_GET_RESOURCE() method of the
   * parent of @p dev and returns the count value.
   */
  rman_res_t
  bus_get_resource_count(device_t dev, int type, int rid)
  {
          rman_res_t start;
          rman_res_t count;
          int error;
  
          error = BUS_GET_RESOURCE(device_get_parent(dev), dev, type, rid,
              &start, &count);
          if (error)
                  return (0);
          return (count);
  }
  
  /**
   * @brief Wrapper function for BUS_DELETE_RESOURCE().
   *
   * This function simply calls the BUS_DELETE_RESOURCE() method of the
   * parent of @p dev.
   */
  void
  bus_delete_resource(device_t dev, int type, int rid)
  {
          BUS_DELETE_RESOURCE(device_get_parent(dev), dev, type, rid);
  }
  
  /**
   * @brief Wrapper function for BUS_CHILD_PRESENT().
   *
   * This function simply calls the BUS_CHILD_PRESENT() method of the
   * parent of @p dev.
   */
  int
  bus_child_present(device_t child)
  {
          return (BUS_CHILD_PRESENT(device_get_parent(child), child));
  }
  
  /**
   * @brief Wrapper function for BUS_CHILD_PNPINFO().
   *
   * This function simply calls the BUS_CHILD_PNPINFO() method of the parent of @p
   * dev.
   */
  int
  bus_child_pnpinfo(device_t child, struct sbuf *sb)
  {
          device_t parent;
  
          parent = device_get_parent(child);
          if (parent == NULL)
                  return (0);
          return (BUS_CHILD_PNPINFO(parent, child, sb));
  }
  
  /**
   * @brief Generic implementation that does nothing for bus_child_pnpinfo
   *
   * This function has the right signature and returns 0 since the sbuf is passed
   * to us to append to.
   */
  int
  bus_generic_child_pnpinfo(device_t dev, device_t child, struct sbuf *sb)
  {
          return (0);
  }
  
  /**
   * @brief Wrapper function for BUS_CHILD_LOCATION().
   *
   * This function simply calls the BUS_CHILD_LOCATION() method of the parent of
   * @p dev.
   */
  int
  bus_child_location(device_t child, struct sbuf *sb)
  {
          device_t parent;
  
          parent = device_get_parent(child);
          if (parent == NULL)
                  return (0);
          return (BUS_CHILD_LOCATION(parent, child, sb));
  }
  
  /**
   * @brief Generic implementation that does nothing for bus_child_location
   *
   * This function has the right signature and returns 0 since the sbuf is passed
   * to us to append to.
   */
  int
  bus_generic_child_location(device_t dev, device_t child, struct sbuf *sb)
  {
          return (0);
  }
  
  /**
   * @brief Wrapper function for BUS_GET_CPUS().
   *
   * This function simply calls the BUS_GET_CPUS() method of the
   * parent of @p dev.
   */
  int
  bus_get_cpus(device_t dev, enum cpu_sets op, size_t setsize, cpuset_t *cpuset)
  {
          device_t parent;
  
          parent = device_get_parent(dev);
          if (parent == NULL)
                  return (EINVAL);
          return (BUS_GET_CPUS(parent, dev, op, setsize, cpuset));
  }
  
  /**
   * @brief Wrapper function for BUS_GET_DMA_TAG().
   *
   * This function simply calls the BUS_GET_DMA_TAG() method of the
   * parent of @p dev.
   */
  bus_dma_tag_t
  bus_get_dma_tag(device_t dev)
  {
          device_t parent;
  
          parent = device_get_parent(dev);
          if (parent == NULL)
                  return (NULL);
          return (BUS_GET_DMA_TAG(parent, dev));
  }
  
  /**
   * @brief Wrapper function for BUS_GET_BUS_TAG().
   *
   * This function simply calls the BUS_GET_BUS_TAG() method of the
   * parent of @p dev.
   */
  bus_space_tag_t
  bus_get_bus_tag(device_t dev)
  {
          device_t parent;
  
          parent = device_get_parent(dev);
          if (parent == NULL)
                  return ((bus_space_tag_t)0);
          return (BUS_GET_BUS_TAG(parent, dev));
  }
  
  /**
   * @brief Wrapper function for BUS_GET_DOMAIN().
   *
   * This function simply calls the BUS_GET_DOMAIN() method of the
   * parent of @p dev.
   */
  int
  bus_get_domain(device_t dev, int *domain)
  {
          return (BUS_GET_DOMAIN(device_get_parent(dev), dev, domain));
  }
  
  /* Resume all devices and then notify userland that we're up again. */
  static int
  root_resume(device_t dev)
  {
          int error;
  
          error = bus_generic_resume(dev);
          if (error == 0) {
                  devctl_notify("kernel", "power", "resume", NULL);
          }
          return (error);
  }
  
  static int
  root_print_child(device_t dev, device_t child)
  {
          int     retval = 0;
  
          retval += bus_print_child_header(dev, child);
          retval += printf("\n");
  
          return (retval);
  }
  
  static int
  root_setup_intr(device_t dev, device_t child, struct resource *irq, int flags,
      driver_filter_t *filter, driver_intr_t *intr, void *arg, void **cookiep)
  {
          /*
           * If an interrupt mapping gets to here something bad has happened.
           */
          panic("root_setup_intr");
  }
  
  /*
   * If we get here, assume that the device is permanent and really is
   * present in the system.  Removable bus drivers are expected to intercept
   * this call long before it gets here.  We return -1 so that drivers that
   * really care can check vs -1 or some ERRNO returned higher in the food
   * chain.
   */
  static int
  root_child_present(device_t dev, device_t child)
  {
          return (-1);
  }
  
  static int
  root_get_cpus(device_t dev, device_t child, enum cpu_sets op, size_t setsize,
      cpuset_t *cpuset)
  {
          switch (op) {
          case INTR_CPUS:
                  /* Default to returning the set of all CPUs. */
                  if (setsize != sizeof(cpuset_t))
                          return (EINVAL);
                  *cpuset = all_cpus;
                  return (0);
          default:
                  return (EINVAL);
          }
  }
  
  static kobj_method_t root_methods[] = {
          /* Device interface */
          KOBJMETHOD(device_shutdown,     bus_generic_shutdown),
          KOBJMETHOD(device_suspend,      bus_generic_suspend),
          KOBJMETHOD(device_resume,       root_resume),
  
          /* Bus interface */
          KOBJMETHOD(bus_print_child,     root_print_child),
          KOBJMETHOD(bus_read_ivar,       bus_generic_read_ivar),
          KOBJMETHOD(bus_write_ivar,      bus_generic_write_ivar),
          KOBJMETHOD(bus_setup_intr,      root_setup_intr),
          KOBJMETHOD(bus_child_present,   root_child_present),
          KOBJMETHOD(bus_get_cpus,        root_get_cpus),
  
          KOBJMETHOD_END
  };
  
  static driver_t root_driver = {
          "root",
          root_methods,
          1,                      /* no softc */
  };
  
  device_t        root_bus;
  devclass_t      root_devclass;
  
  static int
  root_bus_module_handler(module_t mod, int what, void* arg)
  {
          switch (what) {
          case MOD_LOAD:
                  TAILQ_INIT(&bus_data_devices);
                  kobj_class_compile((kobj_class_t) &root_driver);
                  root_bus = make_device(NULL, "root", 0);
                  root_bus->desc = "System root bus";
                  kobj_init((kobj_t) root_bus, (kobj_class_t) &root_driver);
                  root_bus->driver = &root_driver;
                  root_bus->state = DS_ATTACHED;
                  root_devclass = devclass_find_internal("root", NULL, FALSE);
                  devctl2_init();
                  return (0);
  
          case MOD_SHUTDOWN:
                  device_shutdown(root_bus);
                  return (0);
          default:
                  return (EOPNOTSUPP);
          }
  
          return (0);
  }
  
  static moduledata_t root_bus_mod = {
          "rootbus",
          root_bus_module_handler,
          NULL
  };
  DECLARE_MODULE(rootbus, root_bus_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST);
  
  /**
   * @brief Automatically configure devices
   *
   * This function begins the autoconfiguration process by calling
   * device_probe_and_attach() for each child of the @c root0 device.
   */
  void
  root_bus_configure(void)
  {
          PDEBUG(("."));
  
          /* Eventually this will be split up, but this is sufficient for now. */
          bus_set_pass(BUS_PASS_DEFAULT);
  }
  
  /**
   * @brief Module handler for registering device drivers
   *
   * This module handler is used to automatically register device
   * drivers when modules are loaded. If @p what is MOD_LOAD, it calls
   * devclass_add_driver() for the driver described by the
   * driver_module_data structure pointed to by @p arg
   */
  int
  driver_module_handler(module_t mod, int what, void *arg)
  {
          struct driver_module_data *dmd;
          devclass_t bus_devclass;
          kobj_class_t driver;
          int error, pass;
  
          dmd = (struct driver_module_data *)arg;
          bus_devclass = devclass_find_internal(dmd->dmd_busname, NULL, TRUE);
          error = 0;
  
          switch (what) {
          case MOD_LOAD:
                  if (dmd->dmd_chainevh)
                          error = dmd->dmd_chainevh(mod,what,dmd->dmd_chainarg);
  
                  pass = dmd->dmd_pass;
                  driver = dmd->dmd_driver;
                  PDEBUG(("Loading module: driver %s on bus %s (pass %d)",
                      DRIVERNAME(driver), dmd->dmd_busname, pass));
                  error = devclass_add_driver(bus_devclass, driver, pass,
                      dmd->dmd_devclass);
                  break;
  
          case MOD_UNLOAD:
                  PDEBUG(("Unloading module: driver %s from bus %s",
                      DRIVERNAME(dmd->dmd_driver),
                      dmd->dmd_busname));
                  error = devclass_delete_driver(bus_devclass,
                      dmd->dmd_driver);
  
                  if (!error && dmd->dmd_chainevh)
                          error = dmd->dmd_chainevh(mod,what,dmd->dmd_chainarg);
                  break;
          case MOD_QUIESCE:
                  PDEBUG(("Quiesce module: driver %s from bus %s",
                      DRIVERNAME(dmd->dmd_driver),
                      dmd->dmd_busname));
                  error = devclass_quiesce_driver(bus_devclass,
                      dmd->dmd_driver);
  
                  if (!error && dmd->dmd_chainevh)
                          error = dmd->dmd_chainevh(mod,what,dmd->dmd_chainarg);
                  break;
          default:
                  error = EOPNOTSUPP;
                  break;
          }
  
          return (error);
  }
  
  /**
   * @brief Enumerate all hinted devices for this bus.
   *
   * Walks through the hints for this bus and calls the bus_hinted_child
   * routine for each one it fines.  It searches first for the specific
   * bus that's being probed for hinted children (eg isa0), and then for
   * generic children (eg isa).
   *
   * @param       dev     bus device to enumerate
   */
  void
  bus_enumerate_hinted_children(device_t bus)
  {
          int i;
          const char *dname, *busname;
          int dunit;
  
          /*
           * enumerate all devices on the specific bus
           */
          busname = device_get_nameunit(bus);
          i = 0;
          while (resource_find_match(&i, &dname, &dunit, "at", busname) == 0)
                  BUS_HINTED_CHILD(bus, dname, dunit);
  
          /*
           * and all the generic ones.
           */
          busname = device_get_name(bus);
          i = 0;
          while (resource_find_match(&i, &dname, &dunit, "at", busname) == 0)
                  BUS_HINTED_CHILD(bus, dname, dunit);
  }
  
  #ifdef BUS_DEBUG
  
  /* the _short versions avoid iteration by not calling anything that prints
   * more than oneliners. I love oneliners.
   */
  
  static void
  print_device_short(device_t dev, int indent)
  {
          if (!dev)
                  return;
  
          indentprintf(("device %d: <%s> %sparent,%schildren,%s%s%s%s%s,%sivars,%ssoftc,busy=%d\n",
              dev->unit, dev->desc,
              (dev->parent? "":"no "),
              (TAILQ_EMPTY(&dev->children)? "no ":""),
              (dev->flags&DF_ENABLED? "enabled,":"disabled,"),
              (dev->flags&DF_FIXEDCLASS? "fixed,":""),
              (dev->flags&DF_WILDCARD? "wildcard,":""),
              (dev->flags&DF_DESCMALLOCED? "descmalloced,":""),
              (dev->flags&DF_SUSPENDED? "suspended,":""),
              (dev->ivars? "":"no "),
              (dev->softc? "":"no "),
              dev->busy));
  }
  
  static void
  print_device(device_t dev, int indent)
  {
          if (!dev)
                  return;
  
          print_device_short(dev, indent);
  
          indentprintf(("Parent:\n"));
          print_device_short(dev->parent, indent+1);
          indentprintf(("Driver:\n"));
          print_driver_short(dev->driver, indent+1);
          indentprintf(("Devclass:\n"));
          print_devclass_short(dev->devclass, indent+1);
  }
  
  void
  print_device_tree_short(device_t dev, int indent)
  /* print the device and all its children (indented) */
  {
          device_t child;
  
          if (!dev)
                  return;
  
          print_device_short(dev, indent);
  
          TAILQ_FOREACH(child, &dev->children, link) {
                  print_device_tree_short(child, indent+1);
          }
  }
  
  void
  print_device_tree(device_t dev, int indent)
  /* print the device and all its children (indented) */
  {
          device_t child;
  
          if (!dev)
                  return;
  
          print_device(dev, indent);
  
          TAILQ_FOREACH(child, &dev->children, link) {
                  print_device_tree(child, indent+1);
          }
  }
  
  static void
  print_driver_short(driver_t *driver, int indent)
  {
          if (!driver)
                  return;
  
          indentprintf(("driver %s: softc size = %zd\n",
              driver->name, driver->size));
  }
  
  static void
  print_driver(driver_t *driver, int indent)
  {
          if (!driver)
                  return;
  
          print_driver_short(driver, indent);
  }
  
  static void
  print_driver_list(driver_list_t drivers, int indent)
  {
          driverlink_t driver;
  
          TAILQ_FOREACH(driver, &drivers, link) {
                  print_driver(driver->driver, indent);
          }
  }
  
  static void
  print_devclass_short(devclass_t dc, int indent)
  {
          if ( !dc )
                  return;
  
          indentprintf(("devclass %s: max units = %d\n", dc->name, dc->maxunit));
  }
  
  static void
  print_devclass(devclass_t dc, int indent)
  {
          int i;
  
          if ( !dc )
                  return;
  
          print_devclass_short(dc, indent);
          indentprintf(("Drivers:\n"));
          print_driver_list(dc->drivers, indent+1);
  
          indentprintf(("Devices:\n"));
          for (i = 0; i < dc->maxunit; i++)
                  if (dc->devices[i])
                          print_device(dc->devices[i], indent+1);
  }
  
  void
  print_devclass_list_short(void)
  {
          devclass_t dc;
  
          printf("Short listing of devclasses, drivers & devices:\n");
          TAILQ_FOREACH(dc, &devclasses, link) {
                  print_devclass_short(dc, 0);
          }
  }
  
  void
  print_devclass_list(void)
  {
          devclass_t dc;
  
          printf("Full listing of devclasses, drivers & devices:\n");
          TAILQ_FOREACH(dc, &devclasses, link) {
                  print_devclass(dc, 0);
          }
  }
  
  #endif
  
  /*
   * User-space access to the device tree.
   *
   * We implement a small set of nodes:
   *
   * hw.bus                       Single integer read method to obtain the
   *                              current generation count.
   * hw.bus.devices               Reads the entire device tree in flat space.
   * hw.bus.rman                  Resource manager interface
   *
   * We might like to add the ability to scan devclasses and/or drivers to
   * determine what else is currently loaded/available.
   */
  
  static int
  sysctl_bus_info(SYSCTL_HANDLER_ARGS)
  {
          struct u_businfo        ubus;
  
          ubus.ub_version = BUS_USER_VERSION;
          ubus.ub_generation = bus_data_generation;
  
          return (SYSCTL_OUT(req, &ubus, sizeof(ubus)));
  }
  SYSCTL_PROC(_hw_bus, OID_AUTO, info, CTLTYPE_STRUCT | CTLFLAG_RD |
      CTLFLAG_MPSAFE, NULL, 0, sysctl_bus_info, "S,u_businfo",
      "bus-related data");
  
  static int
  sysctl_devices(SYSCTL_HANDLER_ARGS)
  {
          struct sbuf             sb;
          int                     *name = (int *)arg1;
          u_int                   namelen = arg2;
          int                     index;
          device_t                dev;
          struct u_device         *udev;
          int                     error;
  
          if (namelen != 2)
                  return (EINVAL);
  
          if (bus_data_generation_check(name[0]))
                  return (EINVAL);
  
          index = name[1];
  
          /*
           * Scan the list of devices, looking for the requested index.
           */
          TAILQ_FOREACH(dev, &bus_data_devices, devlink) {
                  if (index-- == 0)
                          break;
          }
          if (dev == NULL)
                  return (ENOENT);
  
          /*
           * Populate the return item, careful not to overflow the buffer.
           */
          udev = malloc(sizeof(*udev), M_BUS, M_WAITOK | M_ZERO);
          if (udev == NULL)
                  return (ENOMEM);
          udev->dv_handle = (uintptr_t)dev;
          udev->dv_parent = (uintptr_t)dev->parent;
          udev->dv_devflags = dev->devflags;
          udev->dv_flags = dev->flags;
          udev->dv_state = dev->state;
          sbuf_new(&sb, udev->dv_fields, sizeof(udev->dv_fields), SBUF_FIXEDLEN);
          if (dev->nameunit != NULL)
                  sbuf_cat(&sb, dev->nameunit);
          sbuf_putc(&sb, '\0');
          if (dev->desc != NULL)
                  sbuf_cat(&sb, dev->desc);
          sbuf_putc(&sb, '\0');
          if (dev->driver != NULL)
                  sbuf_cat(&sb, dev->driver->name);
          sbuf_putc(&sb, '\0');
          bus_child_pnpinfo(dev, &sb);
          sbuf_putc(&sb, '\0');
          bus_child_location(dev, &sb);
          sbuf_putc(&sb, '\0');
          error = sbuf_finish(&sb);
          if (error == 0)
                  error = SYSCTL_OUT(req, udev, sizeof(*udev));
          sbuf_delete(&sb);
          free(udev, M_BUS);
          return (error);
  }
  
  SYSCTL_NODE(_hw_bus, OID_AUTO, devices,
      CTLFLAG_RD | CTLFLAG_NEEDGIANT, sysctl_devices,
      "system device tree");
  
  int
  bus_data_generation_check(int generation)
  {
          if (generation != bus_data_generation)
                  return (1);
  
          /* XXX generate optimised lists here? */
          return (0);
  }
  
  void
  bus_data_generation_update(void)
  {
          atomic_add_int(&bus_data_generation, 1);
  }
  
  int
  bus_free_resource(device_t dev, int type, struct resource *r)
  {
          if (r == NULL)
                  return (0);
          return (bus_release_resource(dev, type, rman_get_rid(r), r));
  }
  
  device_t
  device_lookup_by_name(const char *name)
  {
          device_t dev;
  
          TAILQ_FOREACH(dev, &bus_data_devices, devlink) {
                  if (dev->nameunit != NULL && strcmp(dev->nameunit, name) == 0)
                          return (dev);
          }
          return (NULL);
  }
  
  /*
   * /dev/devctl2 implementation.  The existing /dev/devctl device has
   * implicit semantics on open, so it could not be reused for this.
   * Another option would be to call this /dev/bus?
   */
  static int
  find_device(struct devreq *req, device_t *devp)
  {
          device_t dev;
  
          /*
           * First, ensure that the name is nul terminated.
           */
          if (memchr(req->dr_name, '\0', sizeof(req->dr_name)) == NULL)
                  return (EINVAL);
  
          /*
           * Second, try to find an attached device whose name matches
           * 'name'.
           */
          dev = device_lookup_by_name(req->dr_name);
          if (dev != NULL) {
                  *devp = dev;
                  return (0);
          }
  
          /* Finally, give device enumerators a chance. */
          dev = NULL;
          EVENTHANDLER_DIRECT_INVOKE(dev_lookup, req->dr_name, &dev);
          if (dev == NULL)
                  return (ENOENT);
          *devp = dev;
          return (0);
  }
  
  static bool
  driver_exists(device_t bus, const char *driver)
  {
          devclass_t dc;
  
          for (dc = bus->devclass; dc != NULL; dc = dc->parent) {
                  if (devclass_find_driver_internal(dc, driver) != NULL)
                          return (true);
          }
          return (false);
  }
  
  static void
  device_gen_nomatch(device_t dev)
  {
          device_t child;
  
          if (dev->flags & DF_NEEDNOMATCH &&
              dev->state == DS_NOTPRESENT) {
                  device_handle_nomatch(dev);
          }
          dev->flags &= ~DF_NEEDNOMATCH;
          TAILQ_FOREACH(child, &dev->children, link) {
                  device_gen_nomatch(child);
          }
  }
  
  static void
  device_do_deferred_actions(void)
  {
          devclass_t dc;
          driverlink_t dl;
  
          /*
           * Walk through the devclasses to find all the drivers we've tagged as
           * deferred during the freeze and call the driver added routines. They
           * have already been added to the lists in the background, so the driver
           * added routines that trigger a probe will have all the right bidders
           * for the probe auction.
           */
          TAILQ_FOREACH(dc, &devclasses, link) {
                  TAILQ_FOREACH(dl, &dc->drivers, link) {
                          if (dl->flags & DL_DEFERRED_PROBE) {
                                  devclass_driver_added(dc, dl->driver);
                                  dl->flags &= ~DL_DEFERRED_PROBE;
                          }
                  }
          }
  
          /*
           * We also defer no-match events during a freeze. Walk the tree and
           * generate all the pent-up events that are still relevant.
           */
          device_gen_nomatch(root_bus);
          bus_data_generation_update();
  }
  
  static int
  device_get_path(device_t dev, const char *locator, struct sbuf *sb)
  {
          device_t parent;
          int error;
  
          KASSERT(sb != NULL, ("sb is NULL"));
          parent = device_get_parent(dev);
          if (parent == NULL) {
                  error = sbuf_printf(sb, "/");
          } else {
                  error = BUS_GET_DEVICE_PATH(parent, dev, locator, sb);
                  if (error == 0) {
                          error = sbuf_error(sb);
                          if (error == 0 && sbuf_len(sb) <= 1)
                                  error = EIO;
                  }
          }
          sbuf_finish(sb);
          return (error);
  }
  
  static int
  devctl2_ioctl(struct cdev *cdev, u_long cmd, caddr_t data, int fflag,
      struct thread *td)
  {
          struct devreq *req;
          device_t dev;
          int error, old;
  
          /* Locate the device to control. */
          bus_topo_lock();
          req = (struct devreq *)data;
          switch (cmd) {
          case DEV_ATTACH:
          case DEV_DETACH:
          case DEV_ENABLE:
          case DEV_DISABLE:
          case DEV_SUSPEND:
          case DEV_RESUME:
          case DEV_SET_DRIVER:
          case DEV_CLEAR_DRIVER:
          case DEV_RESCAN:
          case DEV_DELETE:
          case DEV_RESET:
                  error = priv_check(td, PRIV_DRIVER);
                  if (error == 0)
                          error = find_device(req, &dev);
                  break;
          case DEV_FREEZE:
          case DEV_THAW:
                  error = priv_check(td, PRIV_DRIVER);
                  break;
          case DEV_GET_PATH:
                  error = find_device(req, &dev);
                  break;
          default:
                  error = ENOTTY;
                  break;
          }
          if (error) {
                  bus_topo_unlock();
                  return (error);
          }
  
          /* Perform the requested operation. */
          switch (cmd) {
          case DEV_ATTACH:
                  if (device_is_attached(dev))
                          error = EBUSY;
                  else if (!device_is_enabled(dev))
                          error = ENXIO;
                  else
                          error = device_probe_and_attach(dev);
                  break;
          case DEV_DETACH:
                  if (!device_is_attached(dev)) {
                          error = ENXIO;
                          break;
                  }
                  if (!(req->dr_flags & DEVF_FORCE_DETACH)) {
                          error = device_quiesce(dev);
                          if (error)
                                  break;
                  }
                  error = device_detach(dev);
                  break;
          case DEV_ENABLE:
                  if (device_is_enabled(dev)) {
                          error = EBUSY;
                          break;
                  }
  
                  /*
                   * If the device has been probed but not attached (e.g.
                   * when it has been disabled by a loader hint), just
                   * attach the device rather than doing a full probe.
                   */
                  device_enable(dev);
                  if (device_is_alive(dev)) {
                          /*
                           * If the device was disabled via a hint, clear
                           * the hint.
                           */
                          if (resource_disabled(dev->driver->name, dev->unit))
                                  resource_unset_value(dev->driver->name,
                                      dev->unit, "disabled");
                          error = device_attach(dev);
                  } else
                          error = device_probe_and_attach(dev);
                  break;
          case DEV_DISABLE:
                  if (!device_is_enabled(dev)) {
                          error = ENXIO;
                          break;
                  }
  
                  if (!(req->dr_flags & DEVF_FORCE_DETACH)) {
                          error = device_quiesce(dev);
                          if (error)
                                  break;
                  }
  
                  /*
                   * Force DF_FIXEDCLASS on around detach to preserve
                   * the existing name.
                   */
                  old = dev->flags;
                  dev->flags |= DF_FIXEDCLASS;
                  error = device_detach(dev);
                  if (!(old & DF_FIXEDCLASS))
                          dev->flags &= ~DF_FIXEDCLASS;
                  if (error == 0)
                          device_disable(dev);
                  break;
          case DEV_SUSPEND:
                  if (device_is_suspended(dev)) {
                          error = EBUSY;
                          break;
                  }
                  if (device_get_parent(dev) == NULL) {
                          error = EINVAL;
                          break;
                  }
                  error = BUS_SUSPEND_CHILD(device_get_parent(dev), dev);
                  break;
          case DEV_RESUME:
                  if (!device_is_suspended(dev)) {
                          error = EINVAL;
                          break;
                  }
                  if (device_get_parent(dev) == NULL) {
                          error = EINVAL;
                          break;
                  }
                  error = BUS_RESUME_CHILD(device_get_parent(dev), dev);
                  break;
          case DEV_SET_DRIVER: {
                  devclass_t dc;
                  char driver[128];
  
                  error = copyinstr(req->dr_data, driver, sizeof(driver), NULL);
                  if (error)
                          break;
                  if (driver[0] == '\0') {
                          error = EINVAL;
                          break;
                  }
                  if (dev->devclass != NULL &&
                      strcmp(driver, dev->devclass->name) == 0)
                          /* XXX: Could possibly force DF_FIXEDCLASS on? */
                          break;
  
                  /*
                   * Scan drivers for this device's bus looking for at
                   * least one matching driver.
                   */
                  if (dev->parent == NULL) {
                          error = EINVAL;
                          break;
                  }
                  if (!driver_exists(dev->parent, driver)) {
                          error = ENOENT;
                          break;
                  }
                  dc = devclass_create(driver);
                  if (dc == NULL) {
                          error = ENOMEM;
                          break;
                  }
  
                  /* Detach device if necessary. */
                  if (device_is_attached(dev)) {
                          if (req->dr_flags & DEVF_SET_DRIVER_DETACH)
                                  error = device_detach(dev);
                          else
                                  error = EBUSY;
                          if (error)
                                  break;
                  }
  
                  /* Clear any previously-fixed device class and unit. */
                  if (dev->flags & DF_FIXEDCLASS)
                          devclass_delete_device(dev->devclass, dev);
                  dev->flags |= DF_WILDCARD;
                  dev->unit = -1;
  
                  /* Force the new device class. */
                  error = devclass_add_device(dc, dev);
                  if (error)
                          break;
                  dev->flags |= DF_FIXEDCLASS;
                  error = device_probe_and_attach(dev);
                  break;
          }
          case DEV_CLEAR_DRIVER:
                  if (!(dev->flags & DF_FIXEDCLASS)) {
                          error = 0;
                          break;
                  }
                  if (device_is_attached(dev)) {
                          if (req->dr_flags & DEVF_CLEAR_DRIVER_DETACH)
                                  error = device_detach(dev);
                          else
                                  error = EBUSY;
                          if (error)
                                  break;
                  }
  
                  dev->flags &= ~DF_FIXEDCLASS;
                  dev->flags |= DF_WILDCARD;
                  devclass_delete_device(dev->devclass, dev);
                  error = device_probe_and_attach(dev);
                  break;
          case DEV_RESCAN:
                  if (!device_is_attached(dev)) {
                          error = ENXIO;
                          break;
                  }
                  error = BUS_RESCAN(dev);
                  break;
          case DEV_DELETE: {
                  device_t parent;
  
                  parent = device_get_parent(dev);
                  if (parent == NULL) {
                          error = EINVAL;
                          break;
                  }
                  if (!(req->dr_flags & DEVF_FORCE_DELETE)) {
                          if (bus_child_present(dev) != 0) {
                                  error = EBUSY;
                                  break;
                          }
                  }
                  
                  error = device_delete_child(parent, dev);
                  break;
          }
          case DEV_FREEZE:
                  if (device_frozen)
                          error = EBUSY;
                  else
                          device_frozen = true;
                  break;
          case DEV_THAW:
                  if (!device_frozen)
                          error = EBUSY;
                  else {
                          device_do_deferred_actions();
                          device_frozen = false;
                  }
                  break;
          case DEV_RESET:
                  if ((req->dr_flags & ~(DEVF_RESET_DETACH)) != 0) {
                          error = EINVAL;
                          break;
                  }
                  error = BUS_RESET_CHILD(device_get_parent(dev), dev,
                      req->dr_flags);
                  break;
          case DEV_GET_PATH: {
                  struct sbuf *sb;
                  char locator[64];
                  ssize_t len;
  
                  error = copyinstr(req->dr_buffer.buffer, locator,
                      sizeof(locator), NULL);
                  if (error != 0)
                          break;
                  sb = sbuf_new(NULL, NULL, 0, SBUF_AUTOEXTEND |
                      SBUF_INCLUDENUL /* | SBUF_WAITOK */);
                  error = device_get_path(dev, locator, sb);
                  if (error == 0) {
                          len = sbuf_len(sb);
                          if (req->dr_buffer.length < len) {
                                  error = ENAMETOOLONG;
                          } else {
                                  error = copyout(sbuf_data(sb),
                                      req->dr_buffer.buffer, len);
                          }
                          req->dr_buffer.length = len;
                  }
                  sbuf_delete(sb);
                  break;
          }
          }
          bus_topo_unlock();
          return (error);
  }
  
  static struct cdevsw devctl2_cdevsw = {
          .d_version =    D_VERSION,
          .d_ioctl =      devctl2_ioctl,
          .d_name =       "devctl2",
  };
  
  static void
  devctl2_init(void)
  {
          make_dev_credf(MAKEDEV_ETERNAL, &devctl2_cdevsw, 0, NULL,
              UID_ROOT, GID_WHEEL, 0644, "devctl2");
  }
  
  /*
   * For maintaining device 'at' location info to avoid recomputing it
   */
  struct device_location_node {
          const char *dln_locator;
          const char *dln_path;
          TAILQ_ENTRY(device_location_node) dln_link;
  };
  typedef TAILQ_HEAD(device_location_list, device_location_node) device_location_list_t;
  
  struct device_location_cache {
          device_location_list_t dlc_list;
  };
  
  
  /*
   * Location cache for wired devices.
   */
  device_location_cache_t *
  dev_wired_cache_init(void)
  {
          device_location_cache_t *dcp;
  
          dcp = malloc(sizeof(*dcp), M_BUS, M_WAITOK | M_ZERO);
          TAILQ_INIT(&dcp->dlc_list);
  
          return (dcp);
  }
  
  void
  dev_wired_cache_fini(device_location_cache_t *dcp)
  {
          struct device_location_node *dln, *tdln;
  
          TAILQ_FOREACH_SAFE(dln, &dcp->dlc_list, dln_link, tdln) {
                  free(dln, M_BUS);
          }
          free(dcp, M_BUS);
  }
  
  static struct device_location_node *
  dev_wired_cache_lookup(device_location_cache_t *dcp, const char *locator)
  {
          struct device_location_node *dln;
  
          TAILQ_FOREACH(dln, &dcp->dlc_list, dln_link) {
                  if (strcmp(locator, dln->dln_locator) == 0)
                          return (dln);
          }
  
          return (NULL);
  }
  
  static struct device_location_node *
  dev_wired_cache_add(device_location_cache_t *dcp, const char *locator, const char *path)
  {
          struct device_location_node *dln;
          size_t loclen, pathlen;
  
          loclen = strlen(locator) + 1;
          pathlen = strlen(path) + 1;
          dln = malloc(sizeof(*dln) + loclen + pathlen, M_BUS, M_WAITOK | M_ZERO);
          dln->dln_locator = (char *)(dln + 1);
          memcpy(__DECONST(char *, dln->dln_locator), locator, loclen);
          dln->dln_path = dln->dln_locator + loclen;
          memcpy(__DECONST(char *, dln->dln_path), path, pathlen);
          TAILQ_INSERT_HEAD(&dcp->dlc_list, dln, dln_link);
  
          return (dln);
  }
  
  bool
  dev_wired_cache_match(device_location_cache_t *dcp, device_t dev,
      const char *at)
  {
          struct sbuf *sb;
          const char *cp;
          char locator[32];
          int error, len;
          struct device_location_node *res;
  
          cp = strchr(at, ':');
          if (cp == NULL)
                  return (false);
          len = cp - at;
          if (len > sizeof(locator) - 1)  /* Skip too long locator */
                  return (false);
          memcpy(locator, at, len);
          locator[len] = '\0';
          cp++;
  
          error = 0;
          /* maybe cache this inside device_t and look that up, but not yet */
          res = dev_wired_cache_lookup(dcp, locator);
          if (res == NULL) {
                  sb = sbuf_new(NULL, NULL, 0, SBUF_AUTOEXTEND |
                      SBUF_INCLUDENUL | SBUF_NOWAIT);
                  if (sb != NULL) {
                          error = device_get_path(dev, locator, sb);
                          if (error == 0) {
                                  res = dev_wired_cache_add(dcp, locator,
                                      sbuf_data(sb));
                          }
                          sbuf_delete(sb);
                  }
          }
          if (error != 0 || res == NULL || res->dln_path == NULL)
                  return (false);
  
          return (strcmp(res->dln_path, cp) == 0);
  }
  
  /*
   * APIs to manage deprecation and obsolescence.
   */
  static int obsolete_panic = 0;
  SYSCTL_INT(_debug, OID_AUTO, obsolete_panic, CTLFLAG_RWTUN, &obsolete_panic, 0,
      "Panic when obsolete features are used (0 = never, 1 = if obsolete, "
      "2 = if deprecated)");
  
  static void
  gone_panic(int major, int running, const char *msg)
  {
          switch (obsolete_panic)
          {
          case 0:
                  return;
          case 1:
                  if (running < major)
                          return;
                  /* FALLTHROUGH */
          default:
                  panic("%s", msg);
          }
  }
  
  void
  _gone_in(int major, const char *msg)
  {
          gone_panic(major, P_OSREL_MAJOR(__FreeBSD_version), msg);
          if (P_OSREL_MAJOR(__FreeBSD_version) >= major)
                  printf("Obsolete code will be removed soon: %s\n", msg);
          else
                  printf("Deprecated code (to be removed in FreeBSD %d): %s\n",
                      major, msg);
  }
  
  void
  _gone_in_dev(device_t dev, int major, const char *msg)
  {
          gone_panic(major, P_OSREL_MAJOR(__FreeBSD_version), msg);
          if (P_OSREL_MAJOR(__FreeBSD_version) >= major)
                  device_printf(dev,
                      "Obsolete code will be removed soon: %s\n", msg);
          else
                  device_printf(dev,
                      "Deprecated code (to be removed in FreeBSD %d): %s\n",
                      major, msg);
  }
  
  #ifdef DDB
  DB_SHOW_COMMAND(device, db_show_device)
  {
          device_t dev;
  
          if (!have_addr)
                  return;
  
          dev = (device_t)addr;
  
          db_printf("name:    %s\n", device_get_nameunit(dev));
          db_printf("  driver:  %s\n", DRIVERNAME(dev->driver));
          db_printf("  class:   %s\n", DEVCLANAME(dev->devclass));
          db_printf("  addr:    %p\n", dev);
          db_printf("  parent:  %p\n", dev->parent);
          db_printf("  softc:   %p\n", dev->softc);
          db_printf("  ivars:   %p\n", dev->ivars);
  }
  
  DB_SHOW_ALL_COMMAND(devices, db_show_all_devices)
  {
          device_t dev;
  
          TAILQ_FOREACH(dev, &bus_data_devices, devlink) {
                  db_show_device((db_expr_t)dev, true, count, modif);
          }
  }
  #endif