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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. |
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