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/interrupt.h>
  27
  28 int pm_active;
  29
  30 /*
  31  *      Locking notes:
  32  *              pm_devs_lock can be a semaphore providing pm ops are not called
  33  *      from an interrupt handler (already a bad idea so no change here). Each
  34  *      change must be protected so that an unlink of an entry doesn't clash
  35  *      with a pm send - which is permitted to sleep in the current architecture
  36  *
  37  *      Module unloads clashing with pm events now work out safely, the module
  38  *      unload path will block until the event has been sent. It may well block
  39  *      until a resume but that will be fine.
  40  */
  41
  42 static DECLARE_MUTEX(pm_devs_lock);
  43 static LIST_HEAD(pm_devs);
  44
  45 /**
  46  *      pm_register - register a device with power management
  47  *      @type: device type
  48  *      @id: device ID
  49  *      @callback: callback function
  50  *
  51  *      Add a device to the list of devices that wish to be notified about
  52  *      power management events. A &pm_dev structure is returned on success,
  53  *      on failure the return is %NULL.
  54  *
  55  *      The callback function will be called in process context and
  56  *      it may sleep.
  57  */
  58
  59 struct pm_dev *pm_register(pm_dev_t type,
  60                            unsigned long id,
  61                            pm_callback callback)
  62 {
  63         struct pm_dev *dev = kmalloc(sizeof(struct pm_dev), GFP_KERNEL);
  64         if (dev) {
  65                 memset(dev, 0, sizeof(*dev));
  66                 dev->type = type;
  67                 dev->id = id;
  68                 dev->callback = callback;
  69
  70                 down(&pm_devs_lock);
  71                 list_add(&dev->entry, &pm_devs);
  72                 up(&pm_devs_lock);
  73         }
  74         return dev;
  75 }
  76
  77 /**
  78  *      pm_unregister -  unregister a device with power management
  79  *      @dev: device to unregister
  80  *
  81  *      Remove a device from the power management notification lists. The
  82  *      dev passed must be a handle previously returned by pm_register.
  83  */
  84
  85 void pm_unregister(struct pm_dev *dev)
  86 {
  87         if (dev) {
  88                 down(&pm_devs_lock);
  89                 list_del(&dev->entry);
  90                 up(&pm_devs_lock);
  91
  92                 kfree(dev);
  93         }
  94 }
  95
  96 static void __pm_unregister(struct pm_dev *dev)
  97 {
  98         if (dev) {
  99                 list_del(&dev->entry);
 100                 kfree(dev);
 101         }
 102 }
 103
 104 /**
 105  *      pm_unregister_all - unregister all devices with matching callback
 106  *      @callback: callback function pointer
 107  *
 108  *      Unregister every device that would call the callback passed. This
 109  *      is primarily meant as a helper function for loadable modules. It
 110  *      enables a module to give up all its managed devices without keeping
 111  *      its own private list.
 112  */
 113
 114 void pm_unregister_all(pm_callback callback)
 115 {
 116         struct list_head *entry;
 117
 118         if (!callback)
 119                 return;
 120
 121         down(&pm_devs_lock);
 122         entry = pm_devs.next;
 123         while (entry != &pm_devs) {
 124                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 125                 entry = entry->next;
 126                 if (dev->callback == callback)
 127                         __pm_unregister(dev);
 128         }
 129         up(&pm_devs_lock);
 130 }
 131
 132 /**
 133  *      pm_send - send request to a single device
 134  *      @dev: device to send to
 135  *      @rqst: power management request
 136  *      @data: data for the callback
 137  *
 138  *      Issue a power management request to a given device. The
 139  *      %PM_SUSPEND and %PM_RESUME events are handled specially. The
 140  *      data field must hold the intended next state. No call is made
 141  *      if the state matches.
 142  *
 143  *      BUGS: what stops two power management requests occurring in parallel
 144  *      and conflicting.
 145  *
 146  *      WARNING: Calling pm_send directly is not generally recommended, in
 147  *      particular there is no locking against the pm_dev going away. The
 148  *      caller must maintain all needed locking or have 'inside knowledge'
 149  *      on the safety. Also remember that this function is not locked against
 150  *      pm_unregister. This means that you must handle SMP races on callback
 151  *      execution and unload yourself.
 152  */
 153
 154 static int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
 155 {
 156         int status = 0;
 157         unsigned long prev_state, next_state;
 158
 159         if (in_interrupt())
 160                 BUG();
 161
 162         switch (rqst) {
 163         case PM_SUSPEND:
 164         case PM_RESUME:
 165                 prev_state = dev->state;
 166                 next_state = (unsigned long) data;
 167                 if (prev_state != next_state) {
 168                         if (dev->callback)
 169                                 status = (*dev->callback)(dev, rqst, data);
 170                         if (!status) {
 171                                 dev->state = next_state;
 172                                 dev->prev_state = prev_state;
 173                         }
 174                 }
 175                 else {
 176                         dev->prev_state = prev_state;
 177                 }
 178                 break;
 179         default:
 180                 if (dev->callback)
 181                         status = (*dev->callback)(dev, rqst, data);
 182                 break;
 183         }
 184         return status;
 185 }
 186
 187 /*
 188  * Undo incomplete request
 189  */
 190 static void pm_undo_all(struct pm_dev *last)
 191 {
 192         struct list_head *entry = last->entry.prev;
 193         while (entry != &pm_devs) {
 194                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 195                 if (dev->state != dev->prev_state) {
 196                         /* previous state was zero (running) resume or
 197                          * previous state was non-zero (suspended) suspend
 198                          */
 199                         pm_request_t undo = (dev->prev_state
 200                                              ? PM_SUSPEND:PM_RESUME);
 201                         pm_send(dev, undo, (void*) dev->prev_state);
 202                 }
 203                 entry = entry->prev;
 204         }
 205 }
 206
 207 /**
 208  *      pm_send_all - send request to all managed devices
 209  *      @rqst: power management request
 210  *      @data: data for the callback
 211  *
 212  *      Issue a power management request to a all devices. The
 213  *      %PM_SUSPEND events are handled specially. Any device is
 214  *      permitted to fail a suspend by returning a non zero (error)
 215  *      value from its callback function. If any device vetoes a
 216  *      suspend request then all other devices that have suspended
 217  *      during the processing of this request are restored to their
 218  *      previous state.
 219  *
 220  *      WARNING:  This function takes the pm_devs_lock. The lock is not dropped until
 221  *      the callbacks have completed. This prevents races against pm locking
 222  *      functions, races against module unload pm_unregister code. It does
 223  *      mean however that you must not issue pm_ functions within the callback
 224  *      or you will deadlock and users will hate you.
 225  *
 226  *      Zero is returned on success. If a suspend fails then the status
 227  *      from the device that vetoes the suspend is returned.
 228  *
 229  *      BUGS: what stops two power management requests occurring in parallel
 230  *      and conflicting.
 231  */
 232
 233 int pm_send_all(pm_request_t rqst, void *data)
 234 {
 235         struct list_head *entry;
 236
 237         down(&pm_devs_lock);
 238         entry = pm_devs.next;
 239         while (entry != &pm_devs) {
 240                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 241                 if (dev->callback) {
 242                         int status = pm_send(dev, rqst, data);
 243                         if (status) {
 244                                 /* return devices to previous state on
 245                                  * failed suspend request
 246                                  */
 247                                 if (rqst == PM_SUSPEND)
 248                                         pm_undo_all(dev);
 249                                 up(&pm_devs_lock);
 250                                 return status;
 251                         }
 252                 }
 253                 entry = entry->next;
 254         }
 255         up(&pm_devs_lock);
 256         return 0;
 257 }
 258
 259 EXPORT_SYMBOL(pm_register);
 260 EXPORT_SYMBOL(pm_unregister);
 261 EXPORT_SYMBOL(pm_unregister_all);
 262 EXPORT_SYMBOL(pm_send_all);
 263 EXPORT_SYMBOL(pm_active);
 264
 265