2 * drivers/base/power/sysfs.c - sysfs entries for device PM
5 #include <linux/device.h>
10 * state - Control current power state of device
12 * show() returns the current power state of the device. '0' indicates
13 * the device is on. Other values (1-3) indicate the device is in a low
16 * store() sets the current power state, which is an integer value
17 * between 0-3. If the device is on ('0'), and the value written is
18 * greater than 0, then the device is placed directly into the low-power
19 * state (via its driver's ->suspend() method).
20 * If the device is currently in a low-power state, and the value is 0,
21 * the device is powered back on (via the ->resume() method).
22 * If the device is in a low-power state, and a different low-power state
23 * is requested, the device is first resumed, then suspended into the new
27 static ssize_t state_show(struct device * dev, struct device_attribute *attr, char * buf)
29 return sprintf(buf, "%u\n", dev->power.power_state.event);
32 static ssize_t state_store(struct device * dev, struct device_attribute *attr, const char * buf, size_t n)
38 state.event = simple_strtoul(buf, &rest, 10);
42 error = dpm_runtime_suspend(dev, state);
44 dpm_runtime_resume(dev);
45 return error ? error : n;
48 static DEVICE_ATTR(state, 0644, state_show, state_store);
52 * wakeup - Report/change current wakeup option for device
54 * Some devices support "wakeup" events, which are hardware signals
55 * used to activate devices from suspended or low power states. Such
56 * devices have one of three values for the sysfs power/wakeup file:
58 * + "enabled\n" to issue the events;
59 * + "disabled\n" not to do so; or
60 * + "\n" for temporary or permanent inability to issue wakeup.
62 * (For example, unconfigured USB devices can't issue wakeups.)
64 * Familiar examples of devices that can issue wakeup events include
65 * keyboards and mice (both PS2 and USB styles), power buttons, modems,
66 * "Wake-On-LAN" Ethernet links, GPIO lines, and more. Some events
67 * will wake the entire system from a suspend state; others may just
68 * wake up the device (if the system as a whole is already active).
69 * Some wakeup events use normal IRQ lines; other use special out
72 * It is the responsibility of device drivers to enable (or disable)
73 * wakeup signaling as part of changing device power states, respecting
74 * the policy choices provided through the driver model.
76 * Devices may not be able to generate wakeup events from all power
77 * states. Also, the events may be ignored in some configurations;
78 * for example, they might need help from other devices that aren't
79 * active, or which may have wakeup disabled. Some drivers rely on
80 * wakeup events internally (unless they are disabled), keeping
81 * their hardware in low power modes whenever they're unused. This
82 * saves runtime power, without requiring system-wide sleep states.
85 static const char enabled[] = "enabled";
86 static const char disabled[] = "disabled";
89 wake_show(struct device * dev, struct device_attribute *attr, char * buf)
91 return sprintf(buf, "%s\n", device_can_wakeup(dev)
92 ? (device_may_wakeup(dev) ? enabled : disabled)
97 wake_store(struct device * dev, struct device_attribute *attr,
98 const char * buf, size_t n)
103 if (!device_can_wakeup(dev))
106 cp = memchr(buf, '\n', n);
109 if (len == sizeof enabled - 1
110 && strncmp(buf, enabled, sizeof enabled - 1) == 0)
111 device_set_wakeup_enable(dev, 1);
112 else if (len == sizeof disabled - 1
113 && strncmp(buf, disabled, sizeof disabled - 1) == 0)
114 device_set_wakeup_enable(dev, 0);
120 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
123 static struct attribute * power_attrs[] = {
124 &dev_attr_state.attr,
125 &dev_attr_wakeup.attr,
128 static struct attribute_group pm_attr_group = {
130 .attrs = power_attrs,
133 int dpm_sysfs_add(struct device * dev)
135 return sysfs_create_group(&dev->kobj, &pm_attr_group);
138 void dpm_sysfs_remove(struct device * dev)
140 sysfs_remove_group(&dev->kobj, &pm_attr_group);