text: /*-
   * 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: src/sys/dev/acpica/acpi_powerres.c,v 1.14.6.1 2003/08/22 20:49:20 jhb Exp $
   */
  
  #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);
  }
  
  