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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.