PM / Sleep: Implement opportunistic sleep, v2
Introduce a mechanism by which the kernel can trigger global
transitions to a sleep state chosen by user space if there are no
active wakeup sources.
It consists of a new sysfs attribute, /sys/power/autosleep, that
can be written one of the strings returned by reads from
/sys/power/state, an ordered workqueue and a work item carrying out
the "suspend" operations. If a string representing the system's
sleep state is written to /sys/power/autosleep, the work item
triggering transitions to that state is queued up and it requeues
itself after every execution until user space writes "off" to
/sys/power/autosleep.
That work item enables the detection of wakeup events using the
functions already defined in drivers/base/power/wakeup.c (with one
small modification) and calls either pm_suspend(), or hibernate() to
put the system into a sleep state. If a wakeup event is reported
while the transition is in progress, it will abort the transition and
the "system suspend" work item will be queued up again.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NeilBrown <neilb@suse.de>
diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index b464d1276..237c735 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -172,3 +172,20 @@
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@sisk.pl>
+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.