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-===========================================
-Power Management Interface for System Sleep
-===========================================
-
-Copyright (c) 2016 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com>
-
-The power management subsystem provides userspace with a unified sysfs interface
-for system sleep regardless of the underlying system architecture or platform.
-The interface is located in the /sys/power/ directory (assuming that sysfs is
-mounted at /sys).
-
-/sys/power/state is the system sleep state control file.
-
-Reading from it returns a list of supported sleep states, encoded as:
-
-- 'freeze' (Suspend-to-Idle)
-- 'standby' (Power-On Suspend)
-- 'mem' (Suspend-to-RAM)
-- 'disk' (Suspend-to-Disk)
-
-Suspend-to-Idle is always supported. Suspend-to-Disk is always supported
-too as long the kernel has been configured to support hibernation at all
-(ie. CONFIG_HIBERNATION is set in the kernel configuration file). Support
-for Suspend-to-RAM and Power-On Suspend depends on the capabilities of the
-platform.
-
-If one of the strings listed in /sys/power/state is written to it, the system
-will attempt to transition into the corresponding sleep state. Refer to
-Documentation/admin-guide/pm/sleep-states.rst for a description of each of
-those states.
-
-/sys/power/disk controls the operating mode of hibernation (Suspend-to-Disk).
-Specifically, it tells the kernel what to do after creating a hibernation image.
-
-Reading from it returns a list of supported options encoded as:
-
-- 'platform' (put the system into sleep using a platform-provided method)
-- 'shutdown' (shut the system down)
-- 'reboot' (reboot the system)
-- 'suspend' (trigger a Suspend-to-RAM transition)
-- 'test_resume' (resume-after-hibernation test mode)
-
-The currently selected option is printed in square brackets.
-
-The 'platform' option is only available if the platform provides a special
-mechanism to put the system to sleep after creating a hibernation image (ACPI
-does that, for example). The 'suspend' option is available if Suspend-to-RAM
-is supported. Refer to Documentation/power/basic-pm-debugging.rst for the
-description of the 'test_resume' option.
-
-To select an option, write the string representing it to /sys/power/disk.
-
-/sys/power/image_size controls the size of hibernation images.
-
-It can be written a string representing a non-negative integer that will be
-used as a best-effort upper limit of the image size, in bytes. The hibernation
-core will do its best to ensure that the image size will not exceed that number.
-However, if that turns out to be impossible to achieve, a hibernation image will
-still be created and its size will be as small as possible. In particular,
-writing '0' to this file will enforce hibernation images to be as small as
-possible.
-
-Reading from this file returns the current image size limit, which is set to
-around 2/5 of available RAM by default.
-
-/sys/power/pm_trace controls the PM trace mechanism saving the last suspend
-or resume event point in the RTC across reboots.
-
-It helps to debug hard lockups or reboots due to device driver failures that
-occur during system suspend or resume (which is more common) more effectively.
-
-If /sys/power/pm_trace contains '1', the fingerprint of each suspend/resume
-event point in turn will be stored in the RTC memory (overwriting the actual
-RTC information), so it will survive a system crash if one occurs right after
-storing it and it can be used later to identify the driver that caused the crash
-to happen (see Documentation/power/s2ram.rst for more information).
-
-Initially it contains '0' which may be changed to '1' by writing a string
-representing a nonzero integer into it.