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1 | What: /sys/devices/.../power/ | ||
2 | Date: January 2009 | ||
3 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | ||
4 | Description: | ||
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 | |||
9 | What: /sys/devices/.../power/wakeup | ||
10 | Date: January 2009 | ||
11 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | ||
12 | Description: | ||
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 | |||
36 | What: /sys/devices/.../power/control | ||
37 | Date: January 2009 | ||
38 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | ||
39 | Description: | ||
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. | ||