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 /*
  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 DEFINE_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                 mutex_lock(&pm_devs_lock);
  70                 list_add(&dev->entry, &pm_devs);
  71                 mutex_unlock(&pm_devs_lock);
  72         }
  73         return dev;
  74 }
  75
  76 /**
  77  *      pm_send - send request to a single device
  78  *      @dev: device to send to
  79  *      @rqst: power management request
  80  *      @data: data for the callback
  81  *
  82  *      Issue a power management request to a given device. The
  83  *      %PM_SUSPEND and %PM_RESUME events are handled specially. The
  84  *      data field must hold the intended next state. No call is made
  85  *      if the state matches.
  86  *
  87  *      BUGS: what stops two power management requests occurring in parallel
  88  *      and conflicting.
  89  *
  90  *      WARNING: Calling pm_send directly is not generally recommended, in
  91  *      particular there is no locking against the pm_dev going away. The
  92  *      caller must maintain all needed locking or have 'inside knowledge'
  93  *      on the safety. Also remember that this function is not locked against
  94  *      pm_unregister. This means that you must handle SMP races on callback
  95  *      execution and unload yourself.
  96  */
  97
  98 static int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
  99 {
 100         int status = 0;
 101         unsigned long prev_state, next_state;
 102
 103         if (in_interrupt())
 104                 BUG();
 105
 106         switch (rqst) {
 107         case PM_SUSPEND:
 108         case PM_RESUME:
 109                 prev_state = dev->state;
 110                 next_state = (unsigned long) data;
 111                 if (prev_state != next_state) {
 112                         if (dev->callback)
 113                                 status = (*dev->callback)(dev, rqst, data);
 114                         if (!status) {
 115                                 dev->state = next_state;
 116                                 dev->prev_state = prev_state;
 117                         }
 118                 }
 119                 else {
 120                         dev->prev_state = prev_state;
 121                 }
 122                 break;
 123         default:
 124                 if (dev->callback)
 125                         status = (*dev->callback)(dev, rqst, data);
 126                 break;
 127         }
 128         return status;
 129 }
 130
 131 /*
 132  * Undo incomplete request
 133  */
 134 static void pm_undo_all(struct pm_dev *last)
 135 {
 136         struct list_head *entry = last->entry.prev;
 137         while (entry != &pm_devs) {
 138                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 139                 if (dev->state != dev->prev_state) {
 140                         /* previous state was zero (running) resume or
 141                          * previous state was non-zero (suspended) suspend
 142                          */
 143                         pm_request_t undo = (dev->prev_state
 144                                              ? PM_SUSPEND:PM_RESUME);
 145                         pm_send(dev, undo, (void*) dev->prev_state);
 146                 }
 147                 entry = entry->prev;
 148         }
 149 }
 150
 151 /**
 152  *      pm_send_all - send request to all managed devices
 153  *      @rqst: power management request
 154  *      @data: data for the callback
 155  *
 156  *      Issue a power management request to a all devices. The
 157  *      %PM_SUSPEND events are handled specially. Any device is
 158  *      permitted to fail a suspend by returning a non zero (error)
 159  *      value from its callback function. If any device vetoes a
 160  *      suspend request then all other devices that have suspended
 161  *      during the processing of this request are restored to their
 162  *      previous state.
 163  *
 164  *      WARNING:  This function takes the pm_devs_lock. The lock is not dropped until
 165  *      the callbacks have completed. This prevents races against pm locking
 166  *      functions, races against module unload pm_unregister code. It does
 167  *      mean however that you must not issue pm_ functions within the callback
 168  *      or you will deadlock and users will hate you.
 169  *
 170  *      Zero is returned on success. If a suspend fails then the status
 171  *      from the device that vetoes the suspend is returned.
 172  *
 173  *      BUGS: what stops two power management requests occurring in parallel
 174  *      and conflicting.
 175  */
 176
 177 int pm_send_all(pm_request_t rqst, void *data)
 178 {
 179         struct list_head *entry;
 180
 181         mutex_lock(&pm_devs_lock);
 182         entry = pm_devs.next;
 183         while (entry != &pm_devs) {
 184                 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
 185                 if (dev->callback) {
 186                         int status = pm_send(dev, rqst, data);
 187                         if (status) {
 188                                 /* return devices to previous state on
 189                                  * failed suspend request
 190                                  */
 191                                 if (rqst == PM_SUSPEND)
 192                                         pm_undo_all(dev);
 193                                 mutex_unlock(&pm_devs_lock);
 194                                 return status;
 195                         }
 196                 }
 197                 entry = entry->next;
 198         }
 199         mutex_unlock(&pm_devs_lock);
 200         return 0;
 201 }
 202
 203 EXPORT_SYMBOL(pm_register);
 204 EXPORT_SYMBOL(pm_send_all);
 205