tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * drivers/base/power/sysfs.c - sysfs entries for device PM
3 */
4
5#include <linux/device.h>
6#include <linux/string.h>
7#include "power.h"
8
9/*
10 * wakeup - Report/change current wakeup option for device
11 *
12 * Some devices support "wakeup" events, which are hardware signals
13 * used to activate devices from suspended or low power states. Such
14 * devices have one of three values for the sysfs power/wakeup file:
15 *
16 * + "enabled\n" to issue the events;
17 * + "disabled\n" not to do so; or
18 * + "\n" for temporary or permanent inability to issue wakeup.
19 *
20 * (For example, unconfigured USB devices can't issue wakeups.)
21 *
22 * Familiar examples of devices that can issue wakeup events include
23 * keyboards and mice (both PS2 and USB styles), power buttons, modems,
24 * "Wake-On-LAN" Ethernet links, GPIO lines, and more. Some events
25 * will wake the entire system from a suspend state; others may just
26 * wake up the device (if the system as a whole is already active).
27 * Some wakeup events use normal IRQ lines; other use special out
28 * of band signaling.
29 *
30 * It is the responsibility of device drivers to enable (or disable)
31 * wakeup signaling as part of changing device power states, respecting
32 * the policy choices provided through the driver model.
33 *
34 * Devices may not be able to generate wakeup events from all power
35 * states. Also, the events may be ignored in some configurations;
36 * for example, they might need help from other devices that aren't
37 * active, or which may have wakeup disabled. Some drivers rely on
38 * wakeup events internally (unless they are disabled), keeping
39 * their hardware in low power modes whenever they're unused. This
40 * saves runtime power, without requiring system-wide sleep states.
41 */
42
43static const char enabled[] = "enabled";
44static const char disabled[] = "disabled";
45
46static ssize_t
47wake_show(struct device * dev, struct device_attribute *attr, char * buf)
48{
49 return sprintf(buf, "%s\n", device_can_wakeup(dev)
50 ? (device_may_wakeup(dev) ? enabled : disabled)
51 : "");
52}
53
54static ssize_t
55wake_store(struct device * dev, struct device_attribute *attr,
56 const char * buf, size_t n)
57{
58 char *cp;
59 int len = n;
60
61 if (!device_can_wakeup(dev))
62 return -EINVAL;
63
64 cp = memchr(buf, '\n', n);
65 if (cp)
66 len = cp - buf;
67 if (len == sizeof enabled - 1
68 && strncmp(buf, enabled, sizeof enabled - 1) == 0)
69 device_set_wakeup_enable(dev, 1);
70 else if (len == sizeof disabled - 1
71 && strncmp(buf, disabled, sizeof disabled - 1) == 0)
72 device_set_wakeup_enable(dev, 0);
73 else
74 return -EINVAL;
75 return n;
76}
77
78static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
79
80
81static struct attribute * power_attrs[] = {
82 &dev_attr_wakeup.attr,
83 NULL,
84};
85static struct attribute_group pm_attr_group = {
86 .name = "power",
87 .attrs = power_attrs,
88};
89
90int dpm_sysfs_add(struct device * dev)
91{
92 return sysfs_create_group(&dev->kobj, &pm_attr_group);
93}
94
95void dpm_sysfs_remove(struct device * dev)
96{
97 sysfs_remove_group(&dev->kobj, &pm_attr_group);
98}