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
21 #include <linux/module.h>
22 #include <linux/spinlock.h>
23 #include <linux/slab.h>
24 #include <linux/pm.h>
25 #include <linux/interrupt.h>
26
27 int pm_active;
28
29 /*
30 * Locking notes:
31 * pm_devs_lock can be a semaphore providing pm ops are not called
32 * from an interrupt handler (already a bad idea so no change here). Each
33 * change must be protected so that an unlink of an entry doesn't clash
34 * with a pm send - which is permitted to sleep in the current architecture
35 *
36 * Module unloads clashing with pm events now work out safely, the module
37 * unload path will block until the event has been sent. It may well block
38 * until a resume but that will be fine.
39 */
40
41 static DECLARE_MUTEX(pm_devs_lock);
42 static LIST_HEAD(pm_devs);
43
44 /**
45 * pm_register - register a device with power management
46 * @type: device type
47 * @id: device ID
48 * @callback: callback function
49 *
50 * Add a device to the list of devices that wish to be notified about
51 * power management events. A &pm_dev structure is returned on success,
52 * on failure the return is %NULL.
53 *
54 * The callback function will be called in process context and
55 * it may sleep.
56 */
57
pm_register(pm_dev_t type,unsigned long id,pm_callback callback)58 struct pm_dev *pm_register(pm_dev_t type,
59 unsigned long id,
60 pm_callback callback)
61 {
62 struct pm_dev *dev = kmalloc(sizeof(struct pm_dev), GFP_KERNEL);
63 if (dev) {
64 memset(dev, 0, sizeof(*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
pm_unregister(struct pm_dev * dev)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
__pm_unregister(struct pm_dev * dev)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
pm_unregister_all(pm_callback callback)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 occuring in parallel
143 * and conflicting.
144 *
145 * WARNING: Calling pm_send directly is not generally recommended, in
146 * paticular 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
pm_send(struct pm_dev * dev,pm_request_t rqst,void * data)153 int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
154 {
155 int status = 0;
156 int 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 */
pm_undo_all(struct pm_dev * last)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 occuring in parallel
229 * and conflicting.
230 */
231
pm_send_all(pm_request_t rqst,void * data)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 /**
259 * pm_find - find a device
260 * @type: type of device
261 * @from: where to start looking
262 *
263 * Scan the power management list for devices of a specific type. The
264 * return value for a matching device may be passed to further calls
265 * to this function to find further matches. A %NULL indicates the end
266 * of the list.
267 *
268 * To search from the beginning pass %NULL as the @from value.
269 *
270 * The caller MUST hold the pm_devs_lock lock when calling this
271 * function. The instant that the lock is dropped all pointers returned
272 * may become invalid.
273 */
274
pm_find(pm_dev_t type,struct pm_dev * from)275 struct pm_dev *pm_find(pm_dev_t type, struct pm_dev *from)
276 {
277 struct list_head *entry = from ? from->entry.next:pm_devs.next;
278 while (entry != &pm_devs) {
279 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
280 if (type == PM_UNKNOWN_DEV || dev->type == type)
281 return dev;
282 entry = entry->next;
283 }
284 return 0;
285 }
286
287 EXPORT_SYMBOL(pm_register);
288 EXPORT_SYMBOL(pm_unregister);
289 EXPORT_SYMBOL(pm_unregister_all);
290 EXPORT_SYMBOL(pm_send);
291 EXPORT_SYMBOL(pm_send_all);
292 EXPORT_SYMBOL(pm_find);
293 EXPORT_SYMBOL(pm_active);
294