836aedb141
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>
23 lines
1 KiB
Text
23 lines
1 KiB
Text
What: /sys/devices/.../real_power_state
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Date: January 2013
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Contact: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Description:
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The /sys/devices/.../real_power_state attribute is only present
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for device objects representing ACPI device nodes that provide
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power management methods and use ACPI power resources for power
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management.
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If present, it contains a string representing the real ACPI
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power state of the given device node as returned by the _PSC
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control method or inferred from the configuration of power
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resources. Its possible values, "D0", "D1", "D2", "D3hot", and
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"D3cold", reflect the power state names defined by the ACPI
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specification (ACPI 4 and above).
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In some situations the value of this attribute may be different
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from the value of the /sys/devices/.../power_state attribute for
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the same device object. If that happens, some shared power
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resources used by the device node are only ON because of some
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other devices using them at the moment.
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This attribute is read-only.
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