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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-01-26 00:51:32 +0400
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-01-26 00:51:32 +0400
commit18a387099b3e3fd901cc706f708b163aa45347b6 (patch)
treecda9262fcb78ab88fcab0530c6cb4128fe7910ce /Documentation/ABI/testing/sysfs-devices-power_resources_D2
parent0bb8f3d6ae621945e6fa2102aa894f72b76a023e (diff)
downloadlinux-18a387099b3e3fd901cc706f708b163aa45347b6.tar.xz
ACPI / PM: Expose lists of device power resources to user space
Since ACPI power resources are going to be used more extensively on new hardware platforms, it is necessary to allow user space (powertop in particular) to look at the lists of power resources corresponding to different power states of devices for diagnostics and control purposes. For this reason, for each power state of an ACPI device node using power resources create a special attribute group under the device node's directory in sysfs containing links to sysfs directories representing the power resources in that list. The names of the new attribute groups are "power_resources_<state>", where <state> is the state name i.e. "D0", "D1", "D2", or "D3hot". Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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+What: /sys/devices/.../power_resources_D2/
+Date: January 2013
+Contact: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+Description:
+ The /sys/devices/.../power_resources_D2/ directory is only
+ present for device objects representing ACPI device nodes that
+ use ACPI power resources for power management and support ACPI
+ power state D2.
+
+ If present, it contains symbolic links to device directories
+ representing ACPI power resources that need to be turned on for
+ the given device node to be in ACPI power state D2. The names
+ of the links are the same as the names of the directories they
+ point to.