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