ia64/linux-2.6.18-xen.hg

view kernel/power/pm.c @ 562:66faefe721eb

pvSCSI backend driver

Signed-off-by: Tomonari Horikoshi <t.horikoshi@jp.fujitsu.com>
Signed-off-by: Jun Kamada <kama@jp.fujitsu.com>
author Keir Fraser <keir.fraser@citrix.com>
date Mon Jun 02 09:58:27 2008 +0100 (2008-06-02)
parents 831230e53067
children
line source
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>
30 int pm_active;
32 /*
33 * Locking notes:
34 * pm_devs_lock can be a semaphore providing pm ops are not called
35 * from an interrupt handler (already a bad idea so no change here). Each
36 * change must be protected so that an unlink of an entry doesn't clash
37 * with a pm send - which is permitted to sleep in the current architecture
38 *
39 * Module unloads clashing with pm events now work out safely, the module
40 * unload path will block until the event has been sent. It may well block
41 * until a resume but that will be fine.
42 */
44 static DEFINE_MUTEX(pm_devs_lock);
45 static LIST_HEAD(pm_devs);
47 /**
48 * pm_register - register a device with power management
49 * @type: device type
50 * @id: device ID
51 * @callback: callback function
52 *
53 * Add a device to the list of devices that wish to be notified about
54 * power management events. A &pm_dev structure is returned on success,
55 * on failure the return is %NULL.
56 *
57 * The callback function will be called in process context and
58 * it may sleep.
59 */
61 struct pm_dev *pm_register(pm_dev_t type,
62 unsigned long id,
63 pm_callback callback)
64 {
65 struct pm_dev *dev = kzalloc(sizeof(struct pm_dev), GFP_KERNEL);
66 if (dev) {
67 dev->type = type;
68 dev->id = id;
69 dev->callback = callback;
71 mutex_lock(&pm_devs_lock);
72 list_add(&dev->entry, &pm_devs);
73 mutex_unlock(&pm_devs_lock);
74 }
75 return dev;
76 }
78 /**
79 * pm_send - send request to a single device
80 * @dev: device to send to
81 * @rqst: power management request
82 * @data: data for the callback
83 *
84 * Issue a power management request to a given device. The
85 * %PM_SUSPEND and %PM_RESUME events are handled specially. The
86 * data field must hold the intended next state. No call is made
87 * if the state matches.
88 *
89 * BUGS: what stops two power management requests occurring in parallel
90 * and conflicting.
91 *
92 * WARNING: Calling pm_send directly is not generally recommended, in
93 * particular there is no locking against the pm_dev going away. The
94 * caller must maintain all needed locking or have 'inside knowledge'
95 * on the safety. Also remember that this function is not locked against
96 * pm_unregister. This means that you must handle SMP races on callback
97 * execution and unload yourself.
98 */
100 static int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
101 {
102 int status = 0;
103 unsigned long prev_state, next_state;
105 if (in_interrupt())
106 BUG();
108 switch (rqst) {
109 case PM_SUSPEND:
110 case PM_RESUME:
111 prev_state = dev->state;
112 next_state = (unsigned long) data;
113 if (prev_state != next_state) {
114 if (dev->callback)
115 status = (*dev->callback)(dev, rqst, data);
116 if (!status) {
117 dev->state = next_state;
118 dev->prev_state = prev_state;
119 }
120 }
121 else {
122 dev->prev_state = prev_state;
123 }
124 break;
125 default:
126 if (dev->callback)
127 status = (*dev->callback)(dev, rqst, data);
128 break;
129 }
130 return status;
131 }
133 /*
134 * Undo incomplete request
135 */
136 static void pm_undo_all(struct pm_dev *last)
137 {
138 struct list_head *entry = last->entry.prev;
139 while (entry != &pm_devs) {
140 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
141 if (dev->state != dev->prev_state) {
142 /* previous state was zero (running) resume or
143 * previous state was non-zero (suspended) suspend
144 */
145 pm_request_t undo = (dev->prev_state
146 ? PM_SUSPEND:PM_RESUME);
147 pm_send(dev, undo, (void*) dev->prev_state);
148 }
149 entry = entry->prev;
150 }
151 }
153 /**
154 * pm_send_all - send request to all managed devices
155 * @rqst: power management request
156 * @data: data for the callback
157 *
158 * Issue a power management request to a all devices. The
159 * %PM_SUSPEND events are handled specially. Any device is
160 * permitted to fail a suspend by returning a non zero (error)
161 * value from its callback function. If any device vetoes a
162 * suspend request then all other devices that have suspended
163 * during the processing of this request are restored to their
164 * previous state.
165 *
166 * WARNING: This function takes the pm_devs_lock. The lock is not dropped until
167 * the callbacks have completed. This prevents races against pm locking
168 * functions, races against module unload pm_unregister code. It does
169 * mean however that you must not issue pm_ functions within the callback
170 * or you will deadlock and users will hate you.
171 *
172 * Zero is returned on success. If a suspend fails then the status
173 * from the device that vetoes the suspend is returned.
174 *
175 * BUGS: what stops two power management requests occurring in parallel
176 * and conflicting.
177 */
179 int pm_send_all(pm_request_t rqst, void *data)
180 {
181 struct list_head *entry;
183 mutex_lock(&pm_devs_lock);
184 entry = pm_devs.next;
185 while (entry != &pm_devs) {
186 struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
187 if (dev->callback) {
188 int status = pm_send(dev, rqst, data);
189 if (status) {
190 /* return devices to previous state on
191 * failed suspend request
192 */
193 if (rqst == PM_SUSPEND)
194 pm_undo_all(dev);
195 mutex_unlock(&pm_devs_lock);
196 return status;
197 }
198 }
199 entry = entry->next;
200 }
201 mutex_unlock(&pm_devs_lock);
202 return 0;
203 }
205 EXPORT_SYMBOL(pm_register);
206 EXPORT_SYMBOL(pm_send_all);
207 EXPORT_SYMBOL(pm_active);