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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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