FreeBSD/Linux Kernel Cross Reference
sys/dev/acpica/acpi_powerres.c

     /*-
      * Copyright (c) 2001 Michael Smith
      * 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.
     *
     *      $FreeBSD: releng/5.1/sys/dev/acpica/acpi_powerres.c 105282 2002-10-16 17:28:53Z jhb $
     */
    
    #include "opt_acpi.h"           /* XXX trim includes */
    #include <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/proc.h>
    #include <sys/malloc.h>
    #include <sys/bus.h>
    #include <sys/conf.h>
    #include <sys/ioccom.h>
    #include <sys/reboot.h>
    #include <sys/sysctl.h>
    #include <sys/systm.h>
    #include <sys/ctype.h>
    
    #include <machine/clock.h>
    
    #include <machine/resource.h>
    
    #include "acpi.h"
    
    #include <dev/acpica/acpivar.h>
    #include <dev/acpica/acpiio.h>
    
    /*
     * ACPI power resource management.
     *
     * Power resource behaviour is slightly complicated by the fact that
     * a single power resource may provide power for more than one device.
     * Thus, we must track the device(s) being powered by a given power
     * resource, and only deactivate it when there are no powered devices.
     *
     * Note that this only manages resources for known devices.  There is an
     * ugly case where we may turn of power to a device which is in use because
     * we don't know that it depends on a given resource.  We should perhaps
     * try to be smarter about this, but a more complete solution would involve
     * scanning all of the ACPI namespace to find devices we're not currently
     * aware of, and this raises questions about whether they should be left 
     * on, turned off, etc.
     *
     * XXX locking
     */
    
    MALLOC_DEFINE(M_ACPIPWR, "acpipwr", "ACPI power resources");
    
    /*
     * Hooks for the ACPI CA debugging infrastructure
     */
    #define _COMPONENT      ACPI_POWER
    ACPI_MODULE_NAME("POWERRES")
    
    /* return values from _STA on a power resource */
    #define ACPI_PWR_OFF    0
    #define ACPI_PWR_ON     1
    
    /*
     * A relationship between a power resource and a consumer.
     */
    struct acpi_powerreference {
        struct acpi_powerconsumer   *ar_consumer;
        struct acpi_powerresource   *ar_resource;
        TAILQ_ENTRY(acpi_powerreference) ar_rlink;  /* link on resource list */
        TAILQ_ENTRY(acpi_powerreference) ar_clink;  /* link on consumer */
    };
        
    /*
     * A power-managed device.
     */
    struct acpi_powerconsumer {
        ACPI_HANDLE         ac_consumer;            /* device which is powered */
        int                 ac_state;
        TAILQ_ENTRY(acpi_powerconsumer) ac_link;
        TAILQ_HEAD(,acpi_powerreference) ac_references;
   };
   
   /*
    * A power resource.
    */
   struct acpi_powerresource {
       TAILQ_ENTRY(acpi_powerresource) ap_link;
       TAILQ_HEAD(,acpi_powerreference) ap_references;
       ACPI_HANDLE         ap_resource;            /* the resource's handle */
       ACPI_INTEGER        ap_systemlevel;
       ACPI_INTEGER        ap_order;
   };
   
   static TAILQ_HEAD(acpi_powerresource_list, acpi_powerresource)  acpi_powerresources;
   static TAILQ_HEAD(acpi_powerconsumer_list, acpi_powerconsumer)  acpi_powerconsumers;
   
   static ACPI_STATUS              acpi_pwr_register_consumer(ACPI_HANDLE consumer);
   static ACPI_STATUS              acpi_pwr_deregister_consumer(ACPI_HANDLE consumer);
   static ACPI_STATUS              acpi_pwr_register_resource(ACPI_HANDLE res);
   static ACPI_STATUS              acpi_pwr_deregister_resource(ACPI_HANDLE res);
   static void                     acpi_pwr_reference_resource(ACPI_OBJECT *obj, void *arg);
   static ACPI_STATUS              acpi_pwr_switch_power(void);
   static struct acpi_powerresource *acpi_pwr_find_resource(ACPI_HANDLE res);
   static struct acpi_powerconsumer *acpi_pwr_find_consumer(ACPI_HANDLE consumer);
   
   /*
    * Initialise our lists.
    */    
   static void
   acpi_pwr_init(void *junk)
   {
       TAILQ_INIT(&acpi_powerresources);
       TAILQ_INIT(&acpi_powerconsumers);
   }
   SYSINIT(acpi_powerresource, SI_SUB_TUNABLES, SI_ORDER_ANY, acpi_pwr_init, NULL);
   
   /*
    * Register a power resource.
    *
    * It's OK to call this if we already know about the resource.
    */
   static ACPI_STATUS
   acpi_pwr_register_resource(ACPI_HANDLE res)
   {
       ACPI_STATUS                 status;
       ACPI_BUFFER                 buf;
       ACPI_OBJECT                 *obj;
       struct acpi_powerresource   *rp, *srp;
   
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       rp = NULL;
       buf.Pointer = NULL;
       
       /* look to see if we know about this resource */
       if (acpi_pwr_find_resource(res) != NULL)
           return_ACPI_STATUS(AE_OK);              /* already know about it */
   
       /* allocate a new resource */
       if ((rp = malloc(sizeof(*rp), M_ACPIPWR, M_NOWAIT | M_ZERO)) == NULL) {
           status = AE_NO_MEMORY;
           goto out;
       }
       TAILQ_INIT(&rp->ap_references);
       rp->ap_resource = res;
   
       /* get the Power Resource object */
       buf.Length = ACPI_ALLOCATE_BUFFER;
       if (ACPI_FAILURE(status = AcpiEvaluateObject(res, NULL, NULL, &buf))) {
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "no power resource object\n"));
           goto out;
       }
       obj = buf.Pointer;
       if (obj->Type != ACPI_TYPE_POWER) {
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "questionable power resource object %s\n", acpi_name(res)));
           status = AE_TYPE;
           goto out;
       }
       rp->ap_systemlevel = obj->PowerResource.SystemLevel;
       rp->ap_order = obj->PowerResource.ResourceOrder;
       
       /* sort the resource into the list */
       status = AE_OK;
       srp = TAILQ_FIRST(&acpi_powerresources);
       if ((srp == NULL) || (rp->ap_order < srp->ap_order)) {
           TAILQ_INSERT_HEAD(&acpi_powerresources, rp, ap_link);
           goto done;
       }
       TAILQ_FOREACH(srp, &acpi_powerresources, ap_link)
           if (rp->ap_order < srp->ap_order) {
               TAILQ_INSERT_BEFORE(srp, rp, ap_link);
               goto done;
           }
       TAILQ_INSERT_TAIL(&acpi_powerresources, rp, ap_link);
   
    done:
       ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "registered power resource %s\n", acpi_name(res)));
    out:
       if (buf.Pointer != NULL)
           AcpiOsFree(buf.Pointer);
       if (ACPI_FAILURE(status) && (rp != NULL))
           free(rp, M_ACPIPWR);
       return_ACPI_STATUS(status);
   }
   
   /*
    * Deregister a power resource.
    */
   static ACPI_STATUS
   acpi_pwr_deregister_resource(ACPI_HANDLE res)
   {
       struct acpi_powerresource   *rp;
   
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       rp = NULL;
       
       /* find the resource */
       if ((rp = acpi_pwr_find_resource(res)) == NULL)
           return_ACPI_STATUS(AE_BAD_PARAMETER);
   
       /* check that there are no consumers referencing this resource */
       if (TAILQ_FIRST(&rp->ap_references) != NULL)
           return_ACPI_STATUS(AE_BAD_PARAMETER);
   
       /* pull it off the list and free it */
       TAILQ_REMOVE(&acpi_powerresources, rp, ap_link);
       free(rp, M_ACPIPWR);
   
       ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "deregistered power resource %s\n", acpi_name(res)));
   
       return_ACPI_STATUS(AE_OK);
   }
   
   /*
    * Register a power consumer.  
    *
    * It's OK to call this if we already know about the consumer.
    */
   static ACPI_STATUS
   acpi_pwr_register_consumer(ACPI_HANDLE consumer)
   {
       struct acpi_powerconsumer   *pc;
       
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       /* check to see whether we know about this consumer already */
       if ((pc = acpi_pwr_find_consumer(consumer)) != NULL)
           return_ACPI_STATUS(AE_OK);
       
       /* allocate a new power consumer */
       if ((pc = malloc(sizeof(*pc), M_ACPIPWR, M_NOWAIT)) == NULL)
           return_ACPI_STATUS(AE_NO_MEMORY);
       TAILQ_INSERT_HEAD(&acpi_powerconsumers, pc, ac_link);
       TAILQ_INIT(&pc->ac_references);
       pc->ac_consumer = consumer;
   
       pc->ac_state = ACPI_STATE_UNKNOWN;  /* XXX we should try to find its current state */
   
       ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "registered power consumer %s\n", acpi_name(consumer)));
       
       return_ACPI_STATUS(AE_OK);
   }
   
   /*
    * Deregister a power consumer.
    *
    * This should only be done once the consumer has been powered off.
    * (XXX is this correct?  Check once implemented)
    */
   static ACPI_STATUS
   acpi_pwr_deregister_consumer(ACPI_HANDLE consumer)
   {
       struct acpi_powerconsumer   *pc;
       
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       /* find the consumer */
       if ((pc = acpi_pwr_find_consumer(consumer)) == NULL)
           return_ACPI_STATUS(AE_BAD_PARAMETER);
       
       /* make sure the consumer's not referencing anything right now */
       if (TAILQ_FIRST(&pc->ac_references) != NULL)
           return_ACPI_STATUS(AE_BAD_PARAMETER);
   
       /* pull the consumer off the list and free it */
       TAILQ_REMOVE(&acpi_powerconsumers, pc, ac_link);
   
       ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "deregistered power consumer %s\n", acpi_name(consumer)));
   
       return_ACPI_STATUS(AE_OK);
   }
   
   /*
    * Set a power consumer to a particular power state.
    */
   ACPI_STATUS
   acpi_pwr_switch_consumer(ACPI_HANDLE consumer, int state)
   {
       struct acpi_powerconsumer   *pc;
       struct acpi_powerreference  *pr;
       ACPI_HANDLE                 method_handle, reslist_handle, pr0_handle;
       ACPI_BUFFER                 reslist_buffer;
       ACPI_OBJECT                 *reslist_object;
       ACPI_STATUS                 status;
       char                        *method_name, *reslist_name;
       int                         res_changed;
   
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       /* find the consumer */
       if ((pc = acpi_pwr_find_consumer(consumer)) == NULL) {
           if (ACPI_FAILURE(status = acpi_pwr_register_consumer(consumer)))
               return_ACPI_STATUS(status);
           if ((pc = acpi_pwr_find_consumer(consumer)) == NULL) {
               return_ACPI_STATUS(AE_ERROR);       /* something very wrong */
           }
       }
   
       /* check for valid transitions */
       if ((pc->ac_state == ACPI_STATE_D3) && (state != ACPI_STATE_D0))
           return_ACPI_STATUS(AE_BAD_PARAMETER);   /* can only go to D0 from D3 */
   
       /* find transition mechanism(s) */
       switch(state) {
       case ACPI_STATE_D0:
           method_name = "_PS0";
           reslist_name = "_PR0";
           break;
       case ACPI_STATE_D1:
           method_name = "_PS1";
           reslist_name = "_PR1";
           break;
       case ACPI_STATE_D2:
           method_name = "_PS2";
           reslist_name = "_PR2";
           break;
       case ACPI_STATE_D3:
           method_name = "_PS3";
           reslist_name = "_PR3";
           break;
       default:
           return_ACPI_STATUS(AE_BAD_PARAMETER);
       }
       ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "setup to switch %s D%d -> D%d\n",
                         acpi_name(consumer), pc->ac_state, state));
   
       /*
        * Verify that this state is supported, ie. one of method or
        * reslist must be present.  We need to do this before we go 
        * dereferencing resources (since we might be trying to go to
        * a state we don't support).
        *
        * Note that if any states are supported, the device has to
        * support D0 and D3.  It's never an error to try to go to
        * D0.
        */
       reslist_buffer.Pointer = NULL;
       reslist_object = NULL;
       if (ACPI_FAILURE(AcpiGetHandle(consumer, method_name, &method_handle)))
           method_handle = NULL;
       if (ACPI_FAILURE(AcpiGetHandle(consumer, reslist_name, &reslist_handle)))
           reslist_handle = NULL;
       if ((reslist_handle == NULL) && (method_handle == NULL)) {
           if (state == ACPI_STATE_D0) {
               pc->ac_state = ACPI_STATE_D0;
               return_ACPI_STATUS(AE_OK);
           }
           if (state != ACPI_STATE_D3) {
               goto bad;
           }
   
           /* turn off the resources listed in _PR0 to go to D3. */
           if (ACPI_FAILURE(AcpiGetHandle(consumer, "_PR0", &pr0_handle))) {
               goto bad;
           }
           reslist_buffer.Length = ACPI_ALLOCATE_BUFFER;
           if (ACPI_FAILURE(status = AcpiEvaluateObject(pr0_handle, NULL, NULL, &reslist_buffer))) {
               goto bad;
           }
           reslist_object = (ACPI_OBJECT *)reslist_buffer.Pointer;
           if ((reslist_object->Type != ACPI_TYPE_PACKAGE) ||
               (reslist_object->Package.Count == 0)) {
               goto bad;
           }
           AcpiOsFree(reslist_buffer.Pointer);
           reslist_buffer.Pointer = NULL;
           reslist_object = NULL;
       }
   
       /*
        * Check that we can actually fetch the list of power resources
        */
       if (reslist_handle != NULL) {
           reslist_buffer.Length = ACPI_ALLOCATE_BUFFER;
           if (ACPI_FAILURE(status = AcpiEvaluateObject(reslist_handle, NULL, NULL, &reslist_buffer))) {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "can't evaluate resource list %s\n",
                                 acpi_name(reslist_handle)));
               goto out;
           }
           reslist_object = (ACPI_OBJECT *)reslist_buffer.Pointer;
           if (reslist_object->Type != ACPI_TYPE_PACKAGE) {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "resource list is not ACPI_TYPE_PACKAGE (%d)\n",
                                 reslist_object->Type));
               status = AE_TYPE;
               goto out;
           }
       }
   
       /*
        * Now we are ready to switch, so  kill off any current power resource references.
        */
       res_changed = 0;
       while((pr = TAILQ_FIRST(&pc->ac_references)) != NULL) {
           res_changed = 1;
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "removing reference to %s\n", acpi_name(pr->ar_resource->ap_resource)));
           TAILQ_REMOVE(&pr->ar_resource->ap_references, pr, ar_rlink);
           TAILQ_REMOVE(&pc->ac_references, pr, ar_clink);
           free(pr, M_ACPIPWR);
       }
   
       /*
        * Add new power resource references, if we have any.  Traverse the
        * package that we got from evaluating reslist_handle, and look up each
        * of the resources that are referenced.
        */
       if (reslist_object != NULL) {
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "referencing %d new resources\n", 
                             reslist_object->Package.Count));
           acpi_ForeachPackageObject(reslist_object, acpi_pwr_reference_resource, pc);
           res_changed = 1;
       }
   
       /*
        * If we changed anything in the resource list, we need to run a switch
        * pass now.
        */
       if (ACPI_FAILURE(status = acpi_pwr_switch_power())) {
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "failed to correctly switch resources to move %s to D%d\n",
                             acpi_name(consumer), state));
           goto out;               /* XXX is this appropriate?  Should we return to previous state? */
       }
   
       /* invoke power state switch method (if present) */
       if (method_handle != NULL) {
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "invoking state transition method %s\n",
                             acpi_name(method_handle)));
           if (ACPI_FAILURE(status = AcpiEvaluateObject(method_handle, NULL, NULL, NULL))) {
                   ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "failed to set state - %s\n",
                                     AcpiFormatException(status)));
                   pc->ac_state = ACPI_STATE_UNKNOWN;
                   goto out;       /* XXX Should we return to previous state? */
           }
       }
           
       /* transition was successful */
       pc->ac_state = state;
       return_ACPI_STATUS(AE_OK);
   
    bad:
       ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "attempt to set unsupported state D%d\n", 
                         state));
       status = AE_BAD_PARAMETER;
   
    out:
       if (reslist_buffer.Pointer != NULL)
           AcpiOsFree(reslist_buffer.Pointer);
       return_ACPI_STATUS(status);
   }
   
   /*
    * Called to create a reference between a power consumer and a power resource
    * identified in the object.
    */
   static void
   acpi_pwr_reference_resource(ACPI_OBJECT *obj, void *arg)
   {
       struct acpi_powerconsumer   *pc = (struct acpi_powerconsumer *)arg;
       struct acpi_powerreference  *pr;
       struct acpi_powerresource   *rp;
       ACPI_HANDLE                 res;
       ACPI_STATUS                 status;
   
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       /* check the object type */
       switch (obj->Type) {
       case ACPI_TYPE_ANY:
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "building reference from %s to %s\n",
                             acpi_name(pc->ac_consumer), acpi_name(obj->Reference.Handle)));
   
           res = obj->Reference.Handle;
           break;
   
       case ACPI_TYPE_STRING:
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "building reference from %s to %s\n",
                             acpi_name(pc->ac_consumer), obj->String.Pointer));
   
           /* get the handle of the resource */
           if (ACPI_FAILURE(status = AcpiGetHandle(NULL, obj->String.Pointer, &res))) {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "couldn't find power resource %s\n", 
                                 obj->String.Pointer));
               return_VOID;
           }
           break;
   
       default:
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "don't know how to create a power reference to object type %d\n", 
                             obj->Type));
           return_VOID;
       }
   
       /* create/look up the resource */
       if (ACPI_FAILURE(status = acpi_pwr_register_resource(res))) {
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "couldn't register power resource %s - %s\n",
                             obj->String.Pointer, AcpiFormatException(status)));
           return_VOID;
       }
       if ((rp = acpi_pwr_find_resource(res)) == NULL) {
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "power resource list corrupted\n"));
           return_VOID;
       }
       ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "found power resource %s\n", acpi_name(rp->ap_resource)));
   
       /* create a reference between the consumer and resource */
       if ((pr = malloc(sizeof(*pr), M_ACPIPWR, M_NOWAIT | M_ZERO)) == NULL) {
           ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "couldn't allocate memory for a power consumer reference\n"));
           return_VOID;
       }
       pr->ar_consumer = pc;
       pr->ar_resource = rp;
       TAILQ_INSERT_TAIL(&pc->ac_references, pr, ar_clink);
       TAILQ_INSERT_TAIL(&rp->ap_references, pr, ar_rlink);
       
       return_VOID;
   }
   
   
   /*
    * Switch power resources to conform to the desired state.
    *
    * Consumers may have modified the power resource list in an arbitrary
    * fashion; we sweep it in sequence order.
    */
   static ACPI_STATUS
   acpi_pwr_switch_power(void)
   {
       struct acpi_powerresource   *rp;
       ACPI_STATUS                 status;
       int                         cur;
   
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       /*
        * Sweep the list forwards turning things on.
        */
       TAILQ_FOREACH(rp, &acpi_powerresources, ap_link) {
           if (TAILQ_FIRST(&rp->ap_references) == NULL) {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "%s has no references, not turning on\n",
                                 acpi_name(rp->ap_resource)));
               continue;
           }
   
           /* we could cache this if we trusted it not to change under us */
           if (ACPI_FAILURE(status = acpi_EvaluateInteger(rp->ap_resource, "_STA", &cur))) {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "can't get status of %s - %d\n",
                                 acpi_name(rp->ap_resource), status));
               continue;   /* XXX is this correct?  Always switch if in doubt? */
           }
   
           /*
            * Switch if required.  Note that we ignore the result of the switch
            * effort; we don't know what to do if it fails, so checking wouldn't
            * help much.
            */
           if (cur != ACPI_PWR_ON) {
               if (ACPI_FAILURE(status = AcpiEvaluateObject(rp->ap_resource, "_ON", NULL, NULL))) {
                   ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "failed to switch %s on - %s\n", 
                                     acpi_name(rp->ap_resource), AcpiFormatException(status)));
               } else {
                   ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "switched %s on\n", acpi_name(rp->ap_resource)));
               }
           } else {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "%s is already on\n", acpi_name(rp->ap_resource)));
           }
       }
       
       /*
        * Sweep the list backwards turning things off.
        */
       TAILQ_FOREACH_REVERSE(rp, &acpi_powerresources, acpi_powerresource_list, ap_link) {
           if (TAILQ_FIRST(&rp->ap_references) != NULL) {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "%s has references, not turning off\n",
                                 acpi_name(rp->ap_resource)));
               continue;
           }
   
           /* we could cache this if we trusted it not to change under us */
           if (ACPI_FAILURE(status = acpi_EvaluateInteger(rp->ap_resource, "_STA", &cur))) {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "can't get status of %s - %d\n",
                                 acpi_name(rp->ap_resource), status));
               continue;   /* XXX is this correct?  Always switch if in doubt? */
           }
   
           /*
            * Switch if required.  Note that we ignore the result of the switch
            * effort; we don't know what to do if it fails, so checking wouldn't
            * help much.
            */
           if (cur != ACPI_PWR_OFF) {
               if (ACPI_FAILURE(status = AcpiEvaluateObject(rp->ap_resource, "_OFF", NULL, NULL))) {
                   ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "failed to switch %s off - %s\n", 
                                     acpi_name(rp->ap_resource), AcpiFormatException(status)));
               } else {
                   ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "switched %s off\n", acpi_name(rp->ap_resource)));
               }
           } else {
               ACPI_DEBUG_PRINT((ACPI_DB_OBJECTS, "%s is already off\n", acpi_name(rp->ap_resource)));
           }
       }
       return_ACPI_STATUS(AE_OK);
   }
   
   /*
    * Find a power resource's control structure.
    */
   static struct acpi_powerresource *
   acpi_pwr_find_resource(ACPI_HANDLE res)
   {
       struct acpi_powerresource   *rp;
       
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       TAILQ_FOREACH(rp, &acpi_powerresources, ap_link)
           if (rp->ap_resource == res)
               break;
       return_PTR(rp);
   }
   
   /*
    * Find a power consumer's control structure.
    */
   static struct acpi_powerconsumer *
   acpi_pwr_find_consumer(ACPI_HANDLE consumer)
   {
       struct acpi_powerconsumer   *pc;
       
       ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
   
       TAILQ_FOREACH(pc, &acpi_powerconsumers, ac_link)
           if (pc->ac_consumer == consumer)
               break;
       return_PTR(pc);
   }
   

Cache object: 503205cf4247abacd75c447767b08094