summaryrefslogtreecommitdiffstats
path: root/kernel/power/pm.c
blob: 84063ac8fcfc95bd15d56dc6778ec45bb503aa43 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
/*
 *  pm.c - Power management interface
 *
 *  Copyright (C) 2000 Andrew Henroid
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/pm.h>
#include <linux/pm_legacy.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>

int pm_active;

/*
 *	Locking notes:
 *		pm_devs_lock can be a semaphore providing pm ops are not called
 *	from an interrupt handler (already a bad idea so no change here). Each
 *	change must be protected so that an unlink of an entry doesn't clash
 *	with a pm send - which is permitted to sleep in the current architecture
 *
 *	Module unloads clashing with pm events now work out safely, the module 
 *	unload path will block until the event has been sent. It may well block
 *	until a resume but that will be fine.
 */
 
static DEFINE_MUTEX(pm_devs_lock);
static LIST_HEAD(pm_devs);

/**
 *	pm_register - register a device with power management
 *	@type: device type 
 *	@id: device ID
 *	@callback: callback function
 *
 *	Add a device to the list of devices that wish to be notified about
 *	power management events. A &pm_dev structure is returned on success,
 *	on failure the return is %NULL.
 *
 *      The callback function will be called in process context and
 *      it may sleep.
 */
 
struct pm_dev *pm_register(pm_dev_t type,
			   unsigned long id,
			   pm_callback callback)
{
	struct pm_dev *dev = kzalloc(sizeof(struct pm_dev), GFP_KERNEL);
	if (dev) {
		dev->type = type;
		dev->id = id;
		dev->callback = callback;

		mutex_lock(&pm_devs_lock);
		list_add(&dev->entry, &pm_devs);
		mutex_unlock(&pm_devs_lock);
	}
	return dev;
}

static void __pm_unregister(struct pm_dev *dev)
{
	if (dev) {
		list_del(&dev->entry);
		kfree(dev);
	}
}

/**
 *	pm_unregister_all - unregister all devices with matching callback
 *	@callback: callback function pointer
 *
 *	Unregister every device that would call the callback passed. This
 *	is primarily meant as a helper function for loadable modules. It
 *	enables a module to give up all its managed devices without keeping
 *	its own private list.
 */
 
void pm_unregister_all(pm_callback callback)
{
	struct list_head *entry;

	if (!callback)
		return;

	mutex_lock(&pm_devs_lock);
	entry = pm_devs.next;
	while (entry != &pm_devs) {
		struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
		entry = entry->next;
		if (dev->callback == callback)
			__pm_unregister(dev);
	}
	mutex_unlock(&pm_devs_lock);
}

/**
 *	pm_send - send request to a single device
 *	@dev: device to send to
 *	@rqst: power management request
 *	@data: data for the callback
 *
 *	Issue a power management request to a given device. The 
 *	%PM_SUSPEND and %PM_RESUME events are handled specially. The
 *	data field must hold the intended next state. No call is made
 *	if the state matches.
 *
 *	BUGS: what stops two power management requests occurring in parallel
 *	and conflicting.
 *
 *	WARNING: Calling pm_send directly is not generally recommended, in
 *	particular there is no locking against the pm_dev going away. The
 *	caller must maintain all needed locking or have 'inside knowledge'
 *	on the safety. Also remember that this function is not locked against
 *	pm_unregister. This means that you must handle SMP races on callback
 *	execution and unload yourself.
 */
 
static int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
{
	int status = 0;
	unsigned long prev_state, next_state;

	if (in_interrupt())
		BUG();

	switch (rqst) {
	case PM_SUSPEND:
	case PM_RESUME:
		prev_state = dev->state;
		next_state = (unsigned long) data;
		if (prev_state != next_state) {
			if (dev->callback)
				status = (*dev->callback)(dev, rqst, data);
			if (!status) {
				dev->state = next_state;
				dev->prev_state = prev_state;
			}
		}
		else {
			dev->prev_state = prev_state;
		}
		break;
	default:
		if (dev->callback)
			status = (*dev->callback)(dev, rqst, data);
		break;
	}
	return status;
}

/*
 * Undo incomplete request
 */
static void pm_undo_all(struct pm_dev *last)
{
	struct list_head *entry = last->entry.prev;
	while (entry != &pm_devs) {
		struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
		if (dev->state != dev->prev_state) {
			/* previous state was zero (running) resume or
			 * previous state was non-zero (suspended) suspend
			 */
			pm_request_t undo = (dev->prev_state
					     ? PM_SUSPEND:PM_RESUME);
			pm_send(dev, undo, (void*) dev->prev_state);
		}
		entry = entry->prev;
	}
}

/**
 *	pm_send_all - send request to all managed devices
 *	@rqst: power management request
 *	@data: data for the callback
 *
 *	Issue a power management request to a all devices. The 
 *	%PM_SUSPEND events are handled specially. Any device is 
 *	permitted to fail a suspend by returning a non zero (error)
 *	value from its callback function. If any device vetoes a 
 *	suspend request then all other devices that have suspended 
 *	during the processing of this request are restored to their
 *	previous state.
 *
 *	WARNING:  This function takes the pm_devs_lock. The lock is not dropped until
 *	the callbacks have completed. This prevents races against pm locking
 *	functions, races against module unload pm_unregister code. It does
 *	mean however that you must not issue pm_ functions within the callback
 *	or you will deadlock and users will hate you.
 *
 *	Zero is returned on success. If a suspend fails then the status
 *	from the device that vetoes the suspend is returned.
 *
 *	BUGS: what stops two power management requests occurring in parallel
 *	and conflicting.
 */
 
int pm_send_all(pm_request_t rqst, void *data)
{
	struct list_head *entry;
	
	mutex_lock(&pm_devs_lock);
	entry = pm_devs.next;
	while (entry != &pm_devs) {
		struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
		if (dev->callback) {
			int status = pm_send(dev, rqst, data);
			if (status) {
				/* return devices to previous state on
				 * failed suspend request
				 */
				if (rqst == PM_SUSPEND)
					pm_undo_all(dev);
				mutex_unlock(&pm_devs_lock);
				return status;
			}
		}
		entry = entry->next;
	}
	mutex_unlock(&pm_devs_lock);
	return 0;
}

EXPORT_SYMBOL(pm_register);
EXPORT_SYMBOL(pm_unregister_all);
EXPORT_SYMBOL(pm_send_all);
EXPORT_SYMBOL(pm_active);