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-rw-r--r--kernel/power/pm.c205
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diff --git a/kernel/power/pm.c b/kernel/power/pm.c
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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
42static DEFINE_MUTEX(pm_devs_lock);
43static 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
59struct 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
98static 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 */
134static 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
177int 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
203EXPORT_SYMBOL(pm_register);
204EXPORT_SYMBOL(pm_send_all);
205
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