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1What: /sys/devices/.../power/
2Date: January 2009
3Contact: Rafael J. Wysocki <rjw@sisk.pl>
4Description:
5 The /sys/devices/.../power directory contains attributes
6 allowing the user space to check and modify some power
7 management related properties of given device.
8
9What: /sys/devices/.../power/wakeup
10Date: January 2009
11Contact: Rafael J. Wysocki <rjw@sisk.pl>
12Description:
13 The /sys/devices/.../power/wakeup attribute allows the user
14 space to check if the device is enabled to wake up the system
15 from sleep states, such as the memory sleep state (suspend to
16 RAM) and hibernation (suspend to disk), and to enable or disable
17 it to do that as desired.
18
19 Some devices support "wakeup" events, which are hardware signals
20 used to activate the system from a sleep state. Such devices
21 have one of the following two values for the sysfs power/wakeup
22 file:
23
24 + "enabled\n" to issue the events;
25 + "disabled\n" not to do so;
26
27 In that cases the user space can change the setting represented
28 by the contents of this file by writing either "enabled", or
29 "disabled" to it.
30
31 For the devices that are not capable of generating system wakeup
32 events this file contains "\n". In that cases the user space
33 cannot modify the contents of this file and the device cannot be
34 enabled to wake up the system.
35
36What: /sys/devices/.../power/control
37Date: January 2009
38Contact: Rafael J. Wysocki <rjw@sisk.pl>
39Description:
40 The /sys/devices/.../power/control attribute allows the user
41 space to control the run-time power management of the device.
42
43 All devices have one of the following two values for the
44 power/control file:
45
46 + "auto\n" to allow the device to be power managed at run time;
47 + "on\n" to prevent the device from being power managed;
48
49 The default for all devices is "auto", which means that they may
50 be subject to automatic power management, depending on their
51 drivers. Changing this attribute to "on" prevents the driver
52 from power managing the device at run time. Doing that while
53 the device is suspended causes it to be woken up.