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