FreeBSD/Linux Kernel Cross Reference
sys/kern/bus_if.m

     #-
     # Copyright (c) 1998-2004 Doug Rabson
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     #
     # Redistribution and use in source and binary forms, with or without
     # modification, are permitted provided that the following conditions
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     # 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
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    #
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    # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    # ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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    # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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    # $FreeBSD$
    #
    
    #include <sys/types.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    
    /**
     * @defgroup BUS bus - KObj methods for drivers of devices with children
     * @brief A set of methods required device drivers that support
     * child devices.
     * @{
     */
    INTERFACE bus;
    
    #
    # Default implementations of some methods.
    #
    CODE {
            static struct resource *
            null_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)
            {
                return (0);
            }
    
            static int
            null_remap_intr(device_t bus, device_t dev, u_int irq)
            {
    
                    if (dev != NULL)
                            return (BUS_REMAP_INTR(dev, NULL, irq));
                    return (ENXIO);
            }
    
            static device_t
            null_add_child(device_t bus, int order, const char *name,
                int unit)
            {
    
                    panic("bus_add_child is not implemented");
            }
    
            static int null_reset_post(device_t bus, device_t dev)
            {
                    return (0);
            }
    
            static int null_reset_prepare(device_t bus, device_t dev)
            {
                    return (0);
            }
    };
    
    /**
     * @brief Print a description of a child device
     *
     * This is called from system code which prints out a description of a
     * device. It should describe the attachment that the child has with
     * the parent. For instance the TurboLaser bus prints which node the
     * device is attached to. See bus_generic_print_child() for more 
     * information.
     *
     * @param _dev          the device whose child is being printed
     * @param _child        the child device to describe
     *
     * @returns             the number of characters output.
     */
    METHOD int print_child {
            device_t _dev;
            device_t _child;
    } DEFAULT bus_generic_print_child;
    
   /**
    * @brief Print a notification about an unprobed child device.
    *
    * Called for each child device that did not succeed in probing for a
    * driver.
    *
    * @param _dev          the device whose child was being probed
    * @param _child        the child device which failed to probe
    */   
   METHOD void probe_nomatch {
           device_t _dev;
           device_t _child;
   };
   
   /**
    * @brief Read the value of a bus-specific attribute of a device
    *
    * This method, along with BUS_WRITE_IVAR() manages a bus-specific set
    * of instance variables of a child device.  The intention is that
    * each different type of bus defines a set of appropriate instance
    * variables (such as ports and irqs for ISA bus etc.)
    *
    * This information could be given to the child device as a struct but
    * that makes it hard for a bus to add or remove variables without
    * forcing an edit and recompile for all drivers which may not be
    * possible for vendor supplied binary drivers.
    *
    * This method copies the value of an instance variable to the
    * location specified by @p *_result.
    * 
    * @param _dev          the device whose child was being examined
    * @param _child        the child device whose instance variable is
    *                      being read
    * @param _index        the instance variable to read
    * @param _result       a location to receive the instance variable
    *                      value
    * 
    * @retval 0            success
    * @retval ENOENT       no such instance variable is supported by @p
    *                      _dev 
    */
   METHOD int read_ivar {
           device_t _dev;
           device_t _child;
           int _index;
           uintptr_t *_result;
   };
   
   /**
    * @brief Write the value of a bus-specific attribute of a device
    * 
    * This method sets the value of an instance variable to @p _value.
    * 
    * @param _dev          the device whose child was being updated
    * @param _child        the child device whose instance variable is
    *                      being written
    * @param _index        the instance variable to write
    * @param _value        the value to write to that instance variable
    * 
    * @retval 0            success
    * @retval ENOENT       no such instance variable is supported by @p
    *                      _dev 
    * @retval EINVAL       the instance variable was recognised but
    *                      contains a read-only value
    */
   METHOD int write_ivar {
           device_t _dev;
           device_t _child;
           int _indx;
           uintptr_t _value;
   };
   
   /**
    * @brief Notify a bus that a child was deleted
    *
    * Called at the beginning of device_delete_child() to allow the parent
    * to teardown any bus-specific state for the child.
    * 
    * @param _dev          the device whose child is being deleted
    * @param _child        the child device which is being deleted
    */
   METHOD void child_deleted {
           device_t _dev;
           device_t _child;
   };
   
   /**
    * @brief Notify a bus that a child was detached
    *
    * Called after the child's DEVICE_DETACH() method to allow the parent
    * to reclaim any resources allocated on behalf of the child.
    * 
    * @param _dev          the device whose child changed state
    * @param _child        the child device which changed state
    */
   METHOD void child_detached {
           device_t _dev;
           device_t _child;
   };
   
   /**
    * @brief Notify a bus that a new driver was added
    * 
    * Called when a new driver is added to the devclass which owns this
    * bus. The generic implementation of this method attempts to probe and
    * attach any un-matched children of the bus.
    * 
    * @param _dev          the device whose devclass had a new driver
    *                      added to it
    * @param _driver       the new driver which was added
    */
   METHOD void driver_added {
           device_t _dev;
           driver_t *_driver;
   } DEFAULT bus_generic_driver_added;
   
   /**
    * @brief Create a new child device
    *
    * For busses which use use drivers supporting DEVICE_IDENTIFY() to
    * enumerate their devices, this method is used to create new
    * device instances. The new device will be added after the last
    * existing child with the same order. Implementations of bus_add_child
    * call device_add_child_ordered to add the child and often add
    * a suitable ivar to the device specific to that bus.
    * 
    * @param _dev          the bus 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
    */
   METHOD device_t add_child {
           device_t _dev;
           u_int _order;
           const char *_name;
           int _unit;
   } DEFAULT null_add_child;
   
   /**
    * @brief Rescan the bus
    *
    * This method is called by a parent bridge or devctl to trigger a bus
    * rescan.  The rescan should delete devices no longer present and
    * enumerate devices that have newly arrived.
    *
    * @param _dev          the bus device
    */
   METHOD int rescan {
           device_t _dev;
   }
   
   /**
    * @brief Allocate a system resource
    *
    * This method is called by child devices of a bus to allocate resources.
    * The types are defined in <machine/resource.h>; the meaning of the
    * resource-ID field varies from bus to bus (but @p *rid == 0 is always
    * valid if the resource type is). If a resource was allocated and the
    * caller did not use the RF_ACTIVE to specify that it should be
    * activated immediately, the caller is responsible for calling
    * BUS_ACTIVATE_RESOURCE() when it actually uses the resource.
    *
    * @param _dev          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
    */
   METHOD struct resource * 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;
   } DEFAULT null_alloc_resource;
   
   /**
    * @brief Activate a resource
    *
    * Activate a resource previously allocated with
    * BUS_ALLOC_RESOURCE().  This may enable decoding of this resource in a
    * device for instance.  It will also establish a mapping for the resource
    * unless RF_UNMAPPED was set when allocating the resource.
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _type         the type of resource
    * @param _rid          the resource identifier
    * @param _r            the resource to activate
    */
   METHOD int activate_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           int             _rid;
           struct resource *_r;
   };
   
   
   /**
    * @brief Map a resource
    *
    * Allocate a mapping for a range of an active resource.  The mapping
    * is described by a struct resource_map object.  This may for instance
    * map a memory region into the kernel's virtual address space.
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _type         the type of resource
    * @param _r            the resource to map
    * @param _args         optional attributes of the mapping
    * @param _map          the mapping
    */
   METHOD int map_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           struct resource *_r;
           struct resource_map_request *_args;
           struct resource_map *_map;
   } DEFAULT bus_generic_map_resource;
   
   
   /**
    * @brief Unmap a resource
    *
    * Release a mapping previously allocated with
    * BUS_MAP_RESOURCE(). This may for instance unmap a memory region
    * from the kernel's virtual address space.
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _type         the type of resource
    * @param _r            the resource
    * @param _map          the mapping to release
    */
   METHOD int unmap_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           struct resource *_r;
           struct resource_map *_map;
   } DEFAULT bus_generic_unmap_resource;
   
   
   /**
    * @brief Deactivate a resource
    *
    * Deactivate a resource previously allocated with
    * BUS_ALLOC_RESOURCE(). 
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _type         the type of resource
    * @param _rid          the resource identifier
    * @param _r            the resource to deactivate
    */
   METHOD int deactivate_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           int             _rid;
           struct resource *_r;
   };
   
   /**
    * @brief Adjust a resource
    *
    * Adjust the start and/or end of a resource allocated by
    * BUS_ALLOC_RESOURCE.  At least part of the new address range must overlap
    * with the existing address range.  If the successful, the resource's range
    * will be adjusted to [start, end] on return.
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _type         the type of resource
    * @param _res          the resource to adjust
    * @param _start        the new starting address of the resource range
    * @param _end          the new ending address of the resource range
    */
   METHOD int adjust_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           struct resource *_res;
           rman_res_t      _start;
           rman_res_t      _end;
   };
   
   /**
    * @brief Release a resource
    *
    * Free a resource allocated by the BUS_ALLOC_RESOURCE.  The @p _rid
    * value must be the same as the one returned by BUS_ALLOC_RESOURCE()
    * (which is not necessarily the same as the one the client passed).
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _type         the type of resource
    * @param _rid          the resource identifier
    * @param _r            the resource to release
    */
   METHOD int release_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           int             _rid;
           struct resource *_res;
   };
   
   /**
    * @brief Install an interrupt handler
    *
    * This method is used to associate an interrupt handler function with
    * an irq resource. When the interrupt triggers, the function @p _intr
    * will be called with the value of @p _arg as its single
    * argument. The value returned in @p *_cookiep is used to cancel the
    * interrupt handler - the caller should save this value to use in a
    * future call to BUS_TEARDOWN_INTR().
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _irq          the resource representing the interrupt
    * @param _flags        a set of bits from enum intr_type specifying
    *                      the class of interrupt
    * @param _intr         the function to call when the interrupt
    *                      triggers
    * @param _arg          a value to use as the single argument in calls
    *                      to @p _intr
    * @param _cookiep      a pointer to a location to receive a cookie
    *                      value that may be used to remove the interrupt
    *                      handler
    */
   METHOD int 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;
   };
   
   /**
    * @brief Uninstall an interrupt handler
    *
    * This method is used to disassociate an interrupt handler function
    * with an irq resource. The value of @p _cookie must be the value
    * returned from a previous call to BUS_SETUP_INTR().
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _irq          the resource representing the interrupt
    * @param _cookie       the cookie value returned when the interrupt
    *                      was originally registered
    */
   METHOD int teardown_intr {
           device_t        _dev;
           device_t        _child;
           struct resource *_irq;
           void            *_cookie;
   };
   
   /**
    * @brief Define a resource which can be allocated with
    * BUS_ALLOC_RESOURCE().
    *
    * This method is used by some busses (typically ISA) to allow a
    * driver to describe a resource range that it would like to
    * allocate. The resource defined by @p _type and @p _rid is defined
    * to start at @p _start and to include @p _count indices in its
    * range.
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which owns the resource
    * @param _type         the type of resource
    * @param _rid          the resource identifier
    * @param _start        the start of the resource range
    * @param _count        the size of the resource range
    */
   METHOD int set_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           int             _rid;
           rman_res_t      _start;
           rman_res_t      _count;
   };
   
   /**
    * @brief Describe a resource
    *
    * This method allows a driver to examine the range used for a given
    * resource without actually allocating it.
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which owns the resource
    * @param _type         the type of resource
    * @param _rid          the resource identifier
    * @param _start        the address of a location to receive the start
    *                      index of the resource range
    * @param _count        the address of a location to receive the size
    *                      of the resource range
    */
   METHOD int get_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           int             _rid;
           rman_res_t      *_startp;
           rman_res_t      *_countp;
   };
   
   /**
    * @brief Delete a resource.
    * 
    * Use this to delete a resource (possibly one previously added with
    * BUS_SET_RESOURCE()).
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which owns the resource
    * @param _type         the type of resource
    * @param _rid          the resource identifier
    */
   METHOD void delete_resource {
           device_t        _dev;
           device_t        _child;
           int             _type;
           int             _rid;
   };
   
   /**
    * @brief Return a struct resource_list.
    *
    * Used by drivers which use bus_generic_rl_alloc_resource() etc. to
    * implement their resource handling. It should return the resource
    * list of the given child device.
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which owns the resource list
    */
   METHOD struct resource_list * get_resource_list {
           device_t        _dev;
           device_t        _child;
   } DEFAULT bus_generic_get_resource_list;
   
   /**
    * @brief Is the hardware described by @p _child still attached to the
    * system?
    *
    * This method should return 0 if the device is not present.  It
    * should return -1 if it is present.  Any errors in determining
    * should be returned as a normal errno value.  Client drivers are to
    * assume that the device is present, even if there is an error
    * determining if it is there.  Busses are to try to avoid returning
    * errors, but newcard will return an error if the device fails to
    * implement this method.
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which is being examined
    */
   METHOD int child_present {
           device_t        _dev;
           device_t        _child;
   } DEFAULT bus_generic_child_present;
   
   /**
    * @brief Returns the pnp info for this device.
    *
    * Return it as a string.  If the storage is insufficient for the
    * string, then return EOVERFLOW.
    *
    * The string must be formatted as a space-separated list of
    * name=value pairs.  Names may only contain alphanumeric characters,
    * underscores ('_') and hyphens ('-').  Values can contain any
    * non-whitespace characters.  Values containing whitespace can be
    * quoted with double quotes ('"').  Double quotes and backslashes in
    * quoted values can be escaped with backslashes ('\').
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which is being examined
    * @param _buf          the address of a buffer to receive the pnp
    *                      string
    * @param _buflen       the size of the buffer pointed to by @p _buf
    */
   METHOD int child_pnpinfo_str {
           device_t        _dev;
           device_t        _child;
           char            *_buf;
           size_t          _buflen;
   };
   
   /**
    * @brief Returns the location for this device.
    *
    * Return it as a string.  If the storage is insufficient for the
    * string, then return EOVERFLOW.
    *
    * The string must be formatted as a space-separated list of
    * name=value pairs.  Names may only contain alphanumeric characters,
    * underscores ('_') and hyphens ('-').  Values can contain any
    * non-whitespace characters.  Values containing whitespace can be
    * quoted with double quotes ('"').  Double quotes and backslashes in
    * quoted values can be escaped with backslashes ('\').
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device which is being examined
    * @param _buf          the address of a buffer to receive the location
    *                      string
    * @param _buflen       the size of the buffer pointed to by @p _buf
    */
   METHOD int child_location_str {
           device_t        _dev;
           device_t        _child;
           char            *_buf;
           size_t          _buflen;
   };
   
   /**
    * @brief Allow drivers to request that an interrupt be bound to a specific
    * CPU.
    * 
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _irq          the resource representing the interrupt
    * @param _cpu          the CPU to bind the interrupt to
    */
   METHOD int bind_intr {
           device_t        _dev;
           device_t        _child;
           struct resource *_irq;
           int             _cpu;
   } DEFAULT bus_generic_bind_intr;
   
   /**
    * @brief Allow (bus) drivers to specify the trigger mode and polarity
    * of the specified interrupt.
    * 
    * @param _dev          the bus device
    * @param _irq          the interrupt number to modify
    * @param _trig         the trigger mode required
    * @param _pol          the interrupt polarity required
    */
   METHOD int config_intr {
           device_t        _dev;
           int             _irq;
           enum intr_trigger _trig;
           enum intr_polarity _pol;
   } DEFAULT bus_generic_config_intr;
   
   /**
    * @brief Allow drivers to associate a description with an active
    * interrupt handler.
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device which allocated the resource
    * @param _irq          the resource representing the interrupt
    * @param _cookie       the cookie value returned when the interrupt
    *                      was originally registered
    * @param _descr        the description to associate with the interrupt
    */
   METHOD int describe_intr {
           device_t        _dev;
           device_t        _child;
           struct resource *_irq;
           void            *_cookie;
           const char      *_descr;
   } DEFAULT bus_generic_describe_intr;
   
   /**
    * @brief Notify a (bus) driver about a child that the hints mechanism
    * believes it has discovered.
    *
    * The bus is responsible for then adding the child in the right order
    * and discovering other things about the child.  The bus driver is
    * free to ignore this hint, to do special things, etc.  It is all up
    * to the bus driver to interpret.
    *
    * This method is only called in response to the parent bus asking for
    * hinted devices to be enumerated.
    *
    * @param _dev          the bus device
    * @param _dname        the name of the device w/o unit numbers
    * @param _dunit        the unit number of the device
    */
   METHOD void hinted_child {
           device_t        _dev;
           const char      *_dname;
           int             _dunit;
   };
   
   /**
    * @brief Returns bus_dma_tag_t for use w/ devices on the bus.
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device to which the tag will belong
    */
   METHOD bus_dma_tag_t get_dma_tag {
           device_t        _dev;
           device_t        _child;
   } DEFAULT bus_generic_get_dma_tag;
   
   /**
    * @brief Returns bus_space_tag_t for use w/ devices on the bus.
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device to which the tag will belong
    */
   METHOD bus_space_tag_t get_bus_tag {
           device_t        _dev;
           device_t        _child;
   } DEFAULT bus_generic_get_bus_tag;
   
   /**
    * @brief Allow the bus to determine the unit number of a device.
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device whose unit is to be wired
    * @param _name         the name of the device's new devclass
    * @param _unitp        a pointer to the device's new unit value
    */
   METHOD void hint_device_unit {
           device_t        _dev;
           device_t        _child;
           const char      *_name;
           int             *_unitp;
   };
   
   /**
    * @brief Notify a bus that the bus pass level has been changed
    *
    * @param _dev          the bus device
    */
   METHOD void new_pass {
           device_t        _dev;
   } DEFAULT bus_generic_new_pass;
   
   /**
    * @brief Notify a bus that specified child's IRQ should be remapped.
    *
    * @param _dev          the bus device
    * @param _child        the child device
    * @param _irq          the irq number
    */
   METHOD int remap_intr {
           device_t        _dev;
           device_t        _child;
           u_int           _irq;
   } DEFAULT null_remap_intr;
   
   /**
    * @brief Suspend a given child
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device to suspend
    */
   METHOD int suspend_child {
           device_t        _dev;
           device_t        _child;
   } DEFAULT bus_generic_suspend_child;
   
   /**
    * @brief Resume a given child
    *
    * @param _dev          the parent device of @p _child
    * @param _child        the device to resume
    */
   METHOD int resume_child {
           device_t        _dev;
           device_t        _child;
   } DEFAULT bus_generic_resume_child;
   
   /**
    * @brief Get the VM domain handle for the given bus and child.
    *
    * @param _dev          the bus device
    * @param _child        the child device
    * @param _domain       a pointer to the bus's domain handle identifier
    */
   METHOD int get_domain {
           device_t        _dev;
           device_t        _child;
           int             *_domain;
   } DEFAULT bus_generic_get_domain;
   
   /**
    * @brief Request a set of CPUs
    *
    * @param _dev          the bus device
    * @param _child        the child device
    * @param _op           type of CPUs to request
    * @param _setsize      the size of the set passed in _cpuset
    * @param _cpuset       a pointer to a cpuset to receive the requested
    *                      set of CPUs
    */
   METHOD int get_cpus {
           device_t        _dev;
           device_t        _child;
           enum cpu_sets   _op;
           size_t          _setsize;
           cpuset_t        *_cpuset;
   } DEFAULT bus_generic_get_cpus;
   
   /**
    * @brief Prepares the given child of the bus for reset
    *
    * Typically bus detaches or suspends children' drivers, and then
    * calls this method to save bus-specific information, for instance,
    * PCI config space, which is damaged by reset.
    *
    * The bus_helper_reset_prepare() helper is provided to ease
    * implementing bus reset methods.
    *
    * @param _dev          the bus device
    * @param _child        the child device
    */
   METHOD int reset_prepare {
           device_t _dev;
           device_t _child;
   } DEFAULT null_reset_prepare;
   
   /**
    * @brief Restores the child operations after the reset
    *
    * The bus_helper_reset_post() helper is provided to ease
    * implementing bus reset methods.
    *
    * @param _dev          the bus device
    * @param _child        the child device
    */
   METHOD int reset_post {
           device_t _dev;
           device_t _child;
   } DEFAULT null_reset_post;
   
   /**
    * @brief Performs reset of the child
    *
    * @param _dev          the bus device
    * @param _child        the child device
    * @param _flags        DEVF_RESET_ flags
    */
   METHOD int reset_child {
           device_t _dev;
           device_t _child;
           int _flags;
   };

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