kernel/power/pm.c

   1 /*
   2  *  pm.c - Power management interface
   3  *
   4  *  Copyright (C) 2000 Andrew Henroid
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, write to the Free Software
  18  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20 #include <linux/init.h>
  21 #include <linux/module.h>
  22 #include <linux/spinlock.h>
  23 #include <linux/mm.h>
  24 #include <linux/slab.h>
  25 #include <linux/pm.h>
  26 #include <linux/pm_legacy.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/mutex.h>
  29
  30 int pm_active;
  31
  32 /*
  33  *      Locking notes:
  34  *              pm_devs_lock can be a semaphore providing pm ops are not called
  35  *      from an interrupt handler (already a bad idea so no change here). Each
  36  *      change must be protected so that an unlink of an entry doesn't clash
  37  *      with a pm send - which is permitted to sleep in the current architecture
  38  *
  39  *      Module unloads clashing with pm events now work out safely, the module
  40  *      unload path will block until the event has been sent. It may well block
  41  *      until a resume but that will be fine.
  42  */
  43
  44 static DEFINE_MUTEX(pm_devs_lock);
  45 static LIST_HEAD(pm_devs);
  46
  47 /**
  48  *      pm_register - register a device with power management
  49  *      @type: device type
  50  *      @id: device ID
  51  *      @callback: callback function
  52  *
  53  *      Add a device to the list of devices that wish to be notified about
  54  *      power management events. A &pm_dev structure is returned on success,
  55  *      on failure the return is %NULL.
  56  *
  57  *      The callback function will be called in process context and
  58  *      it may sleep.
  59  */
  60
  61 struct pm_dev *pm_register(pm_dev_t type,
  62                            unsigned long id,
  63                            pm_callback callback)
  64 {
  65         struct pm_dev *dev = kzalloc(sizeof(struct pm_dev), GFP_KERNEL);
  66         if (dev) {
  67                 dev->type = type;
  68                 dev->id = id;
  69                 dev->callback = callback;
  70
  71                 mutex_lock(&pm_devs_lock);
  72                 list_add(&dev->entry, &pm_devs);
  73                 mutex_unlock(&pm_devs_lock);
  74         }
  75         return dev;
  76 }
  77
  78 /**
  79  *      pm_send - send request to a single device
  80  *      @dev: device to send to
  81  *      @rqst: power management request
  82  *      @data: data for the callback
  83  *
  84  *      Issue a power management request to a given device. The
  85  *      %PM_SUSPEND and %PM_RESUME events are handled specially. The
  86  *      data field must hold the intended next state. No call is made
  87  *      if the state matches.
  88  *
  89  *      BUGS: what stops two power management requests occurring in parallel
  90  *      and conflicting.
  91  *
  92  *      WARNING: Calling pm_send directly is not generally recommended, in
  93  *      particular there is no locking against the pm_dev going away. The
  94  *      caller must maintain all needed locking or have 'inside knowledge'
  95  *      on the safety. Also remember that this function is not locked against
  96  *      pm_unregister. This means that you must handle SMP races on callback
  97  *      execution and unload yourself.
  98  */
  99
 100 static int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
 101 {
 102         int status = 0;
 103         unsigned long prev_state, next_state;
 104
 105         if (in_interrupt())
 106                 BUG();
 107
 108         switch (rqst) {
 109         case PM_SUSPEND:
 110         case PM_RESUME:
 111                 prev_state = dev->state;
 112                 next_state = (unsigned long) data;
 113                 if (prev_state != next_state) {
 114                         if (dev->callback)
 115                                 status = (*dev->callback)(dev, rqst, data);
 116                         if (!status) {
 117                                 dev->state = next_state;
 118                                 dev->prev_state = prev_state;
 119                         }
 120                 }
 121                 else {
 122                         dev->prev_state = prev_state;
 123                 }
 124                 break;
 125         default:
 126                 if (dev->callback)
 127                         status = (*dev->callback)(dev, rqst, data);
 128                 break;
 129         }
 130         return status;
 131 }
 132
 133 /*
 134  * Undo incomplete request
 135  */
 136 static void pm_undo_all(struct pm_dev *last)
 137 {
 138         struct list_head *entry = last->entry.prev;
 139         while (entry != &pm_devs) {
 140                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 141                 if (dev->state != dev->prev_state) {
 142                         /* previous state was zero (running) resume or
 143                          * previous state was non-zero (suspended) suspend
 144                          */
 145                         pm_request_t undo = (dev->prev_state
 146                                              ? PM_SUSPEND:PM_RESUME);
 147                         pm_send(dev, undo, (void*) dev->prev_state);
 148                 }
 149                 entry = entry->prev;
 150         }
 151 }
 152
 153 /**
 154  *      pm_send_all - send request to all managed devices
 155  *      @rqst: power management request
 156  *      @data: data for the callback
 157  *
 158  *      Issue a power management request to a all devices. The
 159  *      %PM_SUSPEND events are handled specially. Any device is
 160  *      permitted to fail a suspend by returning a non zero (error)
 161  *      value from its callback function. If any device vetoes a
 162  *      suspend request then all other devices that have suspended
 163  *      during the processing of this request are restored to their
 164  *      previous state.
 165  *
 166  *      WARNING:  This function takes the pm_devs_lock. The lock is not dropped until
 167  *      the callbacks have completed. This prevents races against pm locking
 168  *      functions, races against module unload pm_unregister code. It does
 169  *      mean however that you must not issue pm_ functions within the callback
 170  *      or you will deadlock and users will hate you.
 171  *
 172  *      Zero is returned on success. If a suspend fails then the status
 173  *      from the device that vetoes the suspend is returned.
 174  *
 175  *      BUGS: what stops two power management requests occurring in parallel
 176  *      and conflicting.
 177  */
 178
 179 int pm_send_all(pm_request_t rqst, void *data)
 180 {
 181         struct list_head *entry;
 182
 183         mutex_lock(&pm_devs_lock);
 184         entry = pm_devs.next;
 185         while (entry != &pm_devs) {
 186                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 187                 if (dev->callback) {
 188                         int status = pm_send(dev, rqst, data);
 189                         if (status) {
 190                                 /* return devices to previous state on
 191                                  * failed suspend request
 192                                  */
 193                                 if (rqst == PM_SUSPEND)
 194                                         pm_undo_all(dev);
 195                                 mutex_unlock(&pm_devs_lock);
 196                                 return status;
 197                         }
 198                 }
 199                 entry = entry->next;
 200         }
 201         mutex_unlock(&pm_devs_lock);
 202         return 0;
 203 }
 204
 205 EXPORT_SYMBOL(pm_register);
 206 EXPORT_SYMBOL(pm_send_all);
 207 EXPORT_SYMBOL(pm_active);
 208
 209