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Subject[PATCH 23/47] PM: add /sys/power documentation to Documentation/ABI
Date
From: Rafael J. Wysocki <rjw@sisk.pl>

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>
---
Documentation/ABI/testing/sysfs-power | 88 +++++++++++++++++++++++++++++++++
1 files changed, 88 insertions(+), 0 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
new file mode 100644
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.
--
1.4.2.1
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