2010-01-24 04:03:22 +07:00
|
|
|
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.
|
2010-01-24 04:25:23 +07:00
|
|
|
|
|
|
|
|
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.
|
