--- /dev/null
+What: /sys/power/
+Date: August 2006
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power directory will contain files that will
+ provide a unified interface to the power management
+ subsystem.
+
+What: /sys/power/state
+Date: May 2014
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/state file controls system sleep states.
+ Reading from this file returns the available sleep state
+ labels, which may be "mem", "standby", "freeze" and "disk"
+ (hibernation). The meanings of the first three labels depend on
+ the relative_sleep_states command line argument as follows:
+ 1) relative_sleep_states = 1
+ "mem", "standby", "freeze" represent non-hibernation sleep
+ states from the deepest ("mem", always present) to the
+ shallowest ("freeze"). "standby" and "freeze" may or may
+ not be present depending on the capabilities of the
+ platform. "freeze" can only be present if "standby" is
+ present.
+ 2) relative_sleep_states = 0 (default)
+ "mem" - "suspend-to-RAM", present if supported.
+ "standby" - "power-on suspend", present if supported.
+ "freeze" - "suspend-to-idle", always present.
+
+ Writing to this file one of these strings causes the system to
+ transition into the corresponding state, if available. See
+ Documentation/power/states.txt for a description of what
+ "suspend-to-RAM", "power-on suspend" and "suspend-to-idle" mean.
+
+What: /sys/power/disk
+Date: September 2006
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/disk file controls the operating mode of the
+ suspend-to-disk mechanism. Reading from this file returns
+ the name of the method by which the system will be put to
+ sleep on the next suspend. There are four methods supported:
+ 'firmware' - means that the memory image will be saved to disk
+ by some firmware, in which case we also assume that the
+ firmware will handle the system suspend.
+ 'platform' - the memory image will be saved by the kernel and
+ the system will be put to sleep by the platform driver (e.g.
+ ACPI or other PM registers).
+ 'shutdown' - the memory image will be saved by the kernel and
+ the system will be powered off.
+ 'reboot' - the memory image will be saved by the kernel and
+ the system will be rebooted.
+
+ Additionally, /sys/power/disk can be used to turn on one of the
+ two testing modes of the suspend-to-disk mechanism: 'testproc'
+ or 'test'. If the suspend-to-disk mechanism is in the
+ 'testproc' mode, writing 'disk' to /sys/power/state will cause
+ the kernel to disable nonboot CPUs and freeze tasks, wait for 5
+ seconds, unfreeze tasks and enable nonboot CPUs. If it is in
+ the 'test' mode, writing 'disk' to /sys/power/state will cause
+ the kernel to disable nonboot CPUs and freeze tasks, shrink
+ memory, suspend devices, wait for 5 seconds, resume devices,
+ unfreeze tasks and enable nonboot CPUs. Then, we are able to
+ look in the log messages and work out, for example, which code
+ is being slow and which device drivers are misbehaving.
+
+ The suspend-to-disk method may be chosen by writing to this
+ file one of the accepted strings:
+
+ 'firmware'
+ 'platform'
+ 'shutdown'
+ 'reboot'
+ 'testproc'
+ 'test'
+
+ It will only change to 'firmware' or 'platform' if the system
+ supports that.
+
+What: /sys/power/image_size
+Date: August 2006
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/image_size file controls the size of the image
+ created by the suspend-to-disk mechanism. It can be written a
+ string representing a non-negative integer that will be used
+ as an upper limit of the image size, in bytes. The kernel's
+ suspend-to-disk code will do its best to ensure the image size
+ will not exceed this number. However, if it turns out to be
+ impossible, the kernel will try to suspend anyway using the
+ smallest image possible. In particular, if "0" is written to
+ this file, the suspend image will be as small as possible.
+
+ Reading from this file will display the current image size
+ limit, which is set to 500 MB by default.
+
+What: /sys/power/pm_trace
+Date: August 2006
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/pm_trace file controls the code which saves the
+ last PM event point in the RTC across reboots, so that you can
+ debug a machine that just hangs during suspend (or more
+ commonly, during resume). Namely, the RTC is only used to save
+ the last PM event point if this file contains '1'. Initially
+ it contains '0' which may be changed to '1' by writing a
+ string representing a nonzero integer into it.
+
+ To use this debugging feature you should attempt to suspend
+ the machine, then reboot it and run
+
+ dmesg -s 1000000 | grep 'hash matches'
+
+ If you do not get any matches (or they appear to be false
+ positives), it is possible that the last PM event point
+ referred to a device created by a loadable kernel module. In
+ this case cat /sys/power/pm_trace_dev_match (see below) after
+ your system is started up and the kernel modules are loaded.
+
+ CAUTION: Using it will cause your machine's real-time (CMOS)
+ clock to be set to a random invalid time after a resume.
+
+What; /sys/power/pm_trace_dev_match
+Date: October 2010
+Contact: James Hogan <james@albanarts.com>
+Description:
+ The /sys/power/pm_trace_dev_match file contains the name of the
+ device associated with the last PM event point saved in the RTC
+ across reboots when pm_trace has been used. More precisely it
+ contains the list of current devices (including those
+ registered by loadable kernel modules since boot) which match
+ the device hash in the RTC at boot, with a newline after each
+ one.
+
+ The advantage of this file over the hash matches printed to the
+ kernel log (see /sys/power/pm_trace), is that it includes
+ devices created after boot by loadable kernel modules.
+
+ Due to the small hash size necessary to fit in the RTC, it is
+ possible that more than one device matches the hash, in which
+ case further investigation is required to determine which
+ device is causing the problem. Note that genuine RTC clock
+ values (such as when pm_trace has not been used), can still
+ match a device and output it's name here.
+
+What: /sys/power/pm_async
+Date: January 2009
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/pm_async file controls the switch allowing the
+ user space to enable or disable asynchronous suspend and resume
+ of devices. If enabled, this feature will cause some device
+ drivers' suspend and resume callbacks to be executed in parallel
+ with each other and with the main suspend thread. It is enabled
+ if this file contains "1", which is the default. It may be
+ disabled by writing "0" to this file, in which case all devices
+ will be suspended and resumed synchronously.
+
+What: /sys/power/wakeup_count
+Date: July 2010
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/wakeup_count file allows user space to put the
+ system into a sleep state while taking into account the
+ concurrent arrival of wakeup events. Reading from it returns
+ the current number of registered wakeup events and it blocks if
+ some wakeup events are being processed at the time the file is
+ read from. Writing to it will only succeed if the current
+ number of wakeup events is equal to the written value and, if
+ successful, will make the kernel abort a subsequent transition
+ to a sleep state if any wakeup events are reported after the
+ write has returned.
+
+What: /sys/power/reserved_size
+Date: May 2011
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/reserved_size file allows user space to control
+ the amount of memory reserved for allocations made by device
+ drivers during the "device freeze" stage of hibernation. It can
+ be written a string representing a non-negative integer that
+ will be used as the amount of memory to reserve for allocations
+ made by device drivers' "freeze" callbacks, in bytes.
+
+ Reading from this file will display the current value, which is
+ set to 1 MB by default.
+
+What: /sys/power/autosleep
+Date: April 2012
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/autosleep file can be written one of the strings
+ returned by reads from /sys/power/state. If that happens, a
+ work item attempting to trigger a transition of the system to
+ the sleep state represented by that string is queued up. This
+ attempt will only succeed if there are no active wakeup sources
+ in the system at that time. After every execution, regardless
+ of whether or not the attempt to put the system to sleep has
+ succeeded, the work item requeues itself until user space
+ writes "off" to /sys/power/autosleep.
+
+ Reading from this file causes the last string successfully
+ written to it to be returned.
+
+What: /sys/power/wake_lock
+Date: February 2012
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/wake_lock file allows user space to create
+ wakeup source objects and activate them on demand (if one of
+ those wakeup sources is active, reads from the
+ /sys/power/wakeup_count file block or return false). When a
+ string without white space is written to /sys/power/wake_lock,
+ it will be assumed to represent a wakeup source name. If there
+ is a wakeup source object with that name, it will be activated
+ (unless active already). Otherwise, a new wakeup source object
+ will be registered, assigned the given name and activated.
+ If a string written to /sys/power/wake_lock contains white
+ space, the part of the string preceding the white space will be
+ regarded as a wakeup source name and handled as descrived above.
+ The other part of the string will be regarded as a timeout (in
+ nanoseconds) such that the wakeup source will be automatically
+ deactivated after it has expired. The timeout, if present, is
+ set regardless of the current state of the wakeup source object
+ in question.
+
+ Reads from this file return a string consisting of the names of
+ wakeup sources created with the help of it that are active at
+ the moment, separated with spaces.
+
+
+What: /sys/power/wake_unlock
+Date: February 2012
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/power/wake_unlock file allows user space to deactivate
+ wakeup sources created with the help of /sys/power/wake_lock.
+ When a string is written to /sys/power/wake_unlock, it will be
+ assumed to represent the name of a wakeup source to deactivate.
+ If a wakeup source object of that name exists and is active at
+ the moment, it will be deactivated.
+
+ Reads from this file return a string consisting of the names of
+ wakeup sources created with the help of /sys/power/wake_lock
+ that are inactive at the moment, separated with spaces.
+
+What: /sys/power/pm_print_times
+Date: May 2012
+Contact: Sameer Nanda <snanda@chromium.org>
+Description:
+ The /sys/power/pm_print_times file allows user space to
+ control whether the time taken by devices to suspend and
+ resume is printed. These prints are useful for hunting down
+ devices that take too long to suspend or resume.
+
+ Writing a "1" enables this printing while writing a "0"
+ disables it. The default value is "0". Reading from this file
+ will display the current value.
Code Review / kvmfornfv.git / blobdiff