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- What: /sys/devices/.../power/
- Date: January 2009
- Contact: Rafael J. Wysocki <rjw@sisk.pl>
- Description:
- The /sys/devices/.../power directory contains attributes
- allowing the user space to check and modify some power
- management related properties of given device.
- What: /sys/devices/.../power/wakeup
- Date: January 2009
- Contact: Rafael J. Wysocki <rjw@sisk.pl>
- Description:
- The /sys/devices/.../power/wakeup attribute allows the user
- space to check if the device is enabled to wake up the system
- from sleep states, such as the memory sleep state (suspend to
- RAM) and hibernation (suspend to disk), and to enable or disable
- it to do that as desired.
- Some devices support "wakeup" events, which are hardware signals
- used to activate the system from a sleep state. Such devices
- have one of the following two values for the sysfs power/wakeup
- file:
- + "enabled\n" to issue the events;
- + "disabled\n" not to do so;
- In that cases the user space can change the setting represented
- by the contents of this file by writing either "enabled", or
- "disabled" to it.
- For the devices that are not capable of generating system wakeup
- events this file contains "\n". In that cases the user space
- cannot modify the contents of this file and the device cannot be
- enabled to wake up the system.
- What: /sys/devices/.../power/control
- Date: January 2009
- Contact: Rafael J. Wysocki <rjw@sisk.pl>
- Description:
- The /sys/devices/.../power/control attribute allows the user
- space to control the run-time power management of the device.
- All devices have one of the following two values for the
- power/control file:
- + "auto\n" to allow the device to be power managed at run time;
- + "on\n" to prevent the device from being power managed;
- The default for all devices is "auto", which means that they may
- be subject to automatic power management, depending on their
- drivers. Changing this attribute to "on" prevents the driver
- from power managing the device at run time. Doing that while
- the device is suspended causes it to be woken up.
- What: /sys/devices/.../power/async
- Date: January 2009
- Contact: Rafael J. Wysocki <rjw@sisk.pl>
- Description:
- The /sys/devices/.../async attribute allows the user space to
- enable or diasble the device's suspend and resume callbacks to
- be executed asynchronously (ie. in separate threads, in parallel
- with the main suspend/resume thread) during system-wide power
- transitions (eg. suspend to RAM, hibernation).
- All devices have one of the following two values for the
- power/async file:
- + "enabled\n" to permit the asynchronous suspend/resume;
- + "disabled\n" to forbid it;
- The value of this attribute may be changed by writing either
- "enabled", or "disabled" to it.
- It generally is unsafe to permit the asynchronous suspend/resume
- of a device unless it is certain that all of the PM dependencies
- of the device are known to the PM core. However, for some
- devices this attribute is set to "enabled" by bus type code or
- device drivers and in that cases it should be safe to leave the
- default value.
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