PM: Make it possible to avoid races between wakeup and system sleep

[linux-2.6-block.git] / Documentation / ABI / testing / sysfs-power

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index d6a801f45b484e4df433ff09e85a6f3bc07707d5..2875f1f74a0792c48402cdc8f33e3e545e0df5ad 100644 (file)
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -114,3 +114,18 @@ Description:
                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@sisk.pl>
+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.