PM: add /sys/power documentation to Documentation/ABI

The file sysfs-power that documents the interface in the /sys/power/ directory
is added to Documentation/ABI/testing.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
new file mode 100644 (file)
index 0000000..d882f80
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-power
@@ -0,0 +1,88 @@
+What:          /sys/power/
+Date:          August 2006
+Contact:       Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+               The /sys/power directory will contain files that will
+               provide a unified interface to the power management
+               subsystem.
+
+What:          /sys/power/state
+Date:          August 2006
+Contact:       Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+               The /sys/power/state file controls the system power state.
+               Reading from this file returns what states are supported,
+               which is hard-coded to 'standby' (Power-On Suspend), 'mem'
+               (Suspend-to-RAM), and 'disk' (Suspend-to-Disk).
+
+               Writing to this file one of these strings causes the system to
+               transition into that state. Please see the file
+               Documentation/power/states.txt for a description of each of
+               these states.
+
+What:          /sys/power/disk
+Date:          August 2006
+Contact:       Rafael J. Wysocki <rjw@sisk.pl>
+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.
+
+               The suspend-to-disk method may be chosen by writing to this
+               file one of the accepted strings:
+
+               'firmware'
+               'platform'
+               'shutdown'
+               'reboot'
+
+               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@sisk.pl>
+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@sisk.pl>
+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'
+
+               CAUTION: Using it will cause your machine's real-time (CMOS)
+               clock to be set to a random invalid time after a resume.