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linux/Documentation/ABI/testing/sysfs-devices-power_state

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ACPI / PM: Expose power states of ACPI devices to user space Make it possible to retrieve the current power state of a device with ACPI power management from user space via sysfs by adding two new attributes, power_state and real_power_state, to the sysfs directory associated with the struct acpi_device object representing the device's ACPI node. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-01-24 19:49:59 +08:00
What: /sys/devices/.../power_state
Date: January 2013
Contact: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Description:
The /sys/devices/.../power_state attribute is only present for
device objects representing ACPI device nodes that provide power
management methods.
If present, it contains a string representing the current ACPI
power state of the given device node. Its possible values,
"D0", "D1", "D2", "D3hot", and "D3cold", reflect the power state
names defined by the ACPI specification (ACPI 4 and above).
If the device node uses shared ACPI power resources, this state
determines a list of power resources required not to be turned
off. However, some power resources needed by the device node in
higher-power (lower-number) states may also be ON because of
some other devices using them at the moment.
This attribute is read-only.