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