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+What: /sys/devices/.../real_power_state
+Date: January 2013
+Contact: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+ 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.