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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.