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ACPI / PM: Expose power states of ACPI devices to user space

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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>
This commit is contained in:
Rafael J. Wysocki
2013-01-24 12:49:59 +01:00
parent cf860be639
commit 836aedb141
3 changed files with 91 additions and 1 deletions
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Documentation/ABI/testing/sysfs-devices-power_state Normal file
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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.

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Documentation/ABI/testing/sysfs-devices-real_power_state Normal file
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What: /sys/devices/.../real_power_state
Date: January 2013
Contact: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Description:
The /sys/devices/.../real_power_state attribute is only present
for device objects representing ACPI device nodes that provide
power management methods and use ACPI power resources for power
management.
If present, it contains a string representing the real ACPI
power state of the given device node as returned by the _PSC
control method or inferred from the configuration of power
resources. Its possible values, "D0", "D1", "D2", "D3hot", and
"D3cold", reflect the power state names defined by the ACPI
specification (ACPI 4 and above).
In some situations the value of this attribute may be different
from the value of the /sys/devices/.../power_state attribute for
the same device object. If that happens, some shared power
resources used by the device node are only ON because of some
other devices using them at the moment.
This attribute is read-only.