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 static void __pm_unregister(struct pm_dev *dev)
  79 {
  80         if (dev) {
  81                 list_del(&dev->entry);
  82                 kfree(dev);
  83         }
  84 }
  85
  86 /**
  87  *      pm_unregister_all - unregister all devices with matching callback
  88  *      @callback: callback function pointer
  89  *
  90  *      Unregister every device that would call the callback passed. This
  91  *      is primarily meant as a helper function for loadable modules. It
  92  *      enables a module to give up all its managed devices without keeping
  93  *      its own private list.
  94  */
  95
  96 void pm_unregister_all(pm_callback callback)
  97 {
  98         struct list_head *entry;
  99
 100         if (!callback)
 101                 return;
 102
 103         mutex_lock(&pm_devs_lock);
 104         entry = pm_devs.next;
 105         while (entry != &pm_devs) {
 106                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 107                 entry = entry->next;
 108                 if (dev->callback == callback)
 109                         __pm_unregister(dev);
 110         }
 111         mutex_unlock(&pm_devs_lock);
 112 }
 113
 114 /**
 115  *      pm_send - send request to a single device
 116  *      @dev: device to send to
 117  *      @rqst: power management request
 118  *      @data: data for the callback
 119  *
 120  *      Issue a power management request to a given device. The
 121  *      %PM_SUSPEND and %PM_RESUME events are handled specially. The
 122  *      data field must hold the intended next state. No call is made
 123  *      if the state matches.
 124  *
 125  *      BUGS: what stops two power management requests occurring in parallel
 126  *      and conflicting.
 127  *
 128  *      WARNING: Calling pm_send directly is not generally recommended, in
 129  *      particular there is no locking against the pm_dev going away. The
 130  *      caller must maintain all needed locking or have 'inside knowledge'
 131  *      on the safety. Also remember that this function is not locked against
 132  *      pm_unregister. This means that you must handle SMP races on callback
 133  *      execution and unload yourself.
 134  */
 135
 136 static int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
 137 {
 138         int status = 0;
 139         unsigned long prev_state, next_state;
 140
 141         if (in_interrupt())
 142                 BUG();
 143
 144         switch (rqst) {
 145         case PM_SUSPEND:
 146         case PM_RESUME:
 147                 prev_state = dev->state;
 148                 next_state = (unsigned long) data;
 149                 if (prev_state != next_state) {
 150                         if (dev->callback)
 151                                 status = (*dev->callback)(dev, rqst, data);
 152                         if (!status) {
 153                                 dev->state = next_state;
 154                                 dev->prev_state = prev_state;
 155                         }
 156                 }
 157                 else {
 158                         dev->prev_state = prev_state;
 159                 }
 160                 break;
 161         default:
 162                 if (dev->callback)
 163                         status = (*dev->callback)(dev, rqst, data);
 164                 break;
 165         }
 166         return status;
 167 }
 168
 169 /*
 170  * Undo incomplete request
 171  */
 172 static void pm_undo_all(struct pm_dev *last)
 173 {
 174         struct list_head *entry = last->entry.prev;
 175         while (entry != &pm_devs) {
 176                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 177                 if (dev->state != dev->prev_state) {
 178                         /* previous state was zero (running) resume or
 179                          * previous state was non-zero (suspended) suspend
 180                          */
 181                         pm_request_t undo = (dev->prev_state
 182                                              ? PM_SUSPEND:PM_RESUME);
 183                         pm_send(dev, undo, (void*) dev->prev_state);
 184                 }
 185                 entry = entry->prev;
 186         }
 187 }
 188
 189 /**
 190  *      pm_send_all - send request to all managed devices
 191  *      @rqst: power management request
 192  *      @data: data for the callback
 193  *
 194  *      Issue a power management request to a all devices. The
 195  *      %PM_SUSPEND events are handled specially. Any device is
 196  *      permitted to fail a suspend by returning a non zero (error)
 197  *      value from its callback function. If any device vetoes a
 198  *      suspend request then all other devices that have suspended
 199  *      during the processing of this request are restored to their
 200  *      previous state.
 201  *
 202  *      WARNING:  This function takes the pm_devs_lock. The lock is not dropped until
 203  *      the callbacks have completed. This prevents races against pm locking
 204  *      functions, races against module unload pm_unregister code. It does
 205  *      mean however that you must not issue pm_ functions within the callback
 206  *      or you will deadlock and users will hate you.
 207  *
 208  *      Zero is returned on success. If a suspend fails then the status
 209  *      from the device that vetoes the suspend is returned.
 210  *
 211  *      BUGS: what stops two power management requests occurring in parallel
 212  *      and conflicting.
 213  */
 214
 215 int pm_send_all(pm_request_t rqst, void *data)
 216 {
 217         struct list_head *entry;
 218
 219         mutex_lock(&pm_devs_lock);
 220         entry = pm_devs.next;
 221         while (entry != &pm_devs) {
 222                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 223                 if (dev->callback) {
 224                         int status = pm_send(dev, rqst, data);
 225                         if (status) {
 226                                 /* return devices to previous state on
 227                                  * failed suspend request
 228                                  */
 229                                 if (rqst == PM_SUSPEND)
 230                                         pm_undo_all(dev);
 231                                 mutex_unlock(&pm_devs_lock);
 232                                 return status;
 233                         }
 234                 }
 235                 entry = entry->next;
 236         }
 237         mutex_unlock(&pm_devs_lock);
 238         return 0;
 239 }
 240
 241 EXPORT_SYMBOL(pm_register);
 242 EXPORT_SYMBOL(pm_unregister_all);
 243 EXPORT_SYMBOL(pm_send_all);
 244 EXPORT_SYMBOL(pm_active);
 245
 246