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authorBernie Thompson <bhthompson@chromium.org>2013-07-03 15:07:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-03 16:07:54 -0700
commit1df0a4711f6e93c1073dd82f6e7905748842e2b3 (patch)
tree4a885c99a414d23d5be468b75aa8ea68109d1081 /Documentation/rtc.txt
parentc67d96e317510e63e8a24d3a5742dd47b21c3340 (diff)
downloadlinux-linaro-stable-1df0a4711f6e93c1073dd82f6e7905748842e2b3.tar.gz
rtc: add ability to push out an existing wakealarm using sysfs
This adds the ability for the rtc sysfs code to handle += characters at the beginning of a wakealarm setting string. This will allow the user to attempt to push out an existing wakealarm by a provided amount. In the case that the += characters are provided but the alarm is not active -EINVAL is returned. his is useful, at least for my purposes in suspend/resume testing. The basic test goes something like: 1. Set a wake alarm from userspace 5 seconds in the future 2. Start the suspend process (echo mem > /sys/power/state) 3. After ~2.5 seconds if userspace is still running (using another thread to check this), move the wake alarm 5 more seconds If the "move" involves an unset of the wakealarm then there's a period of time where the system is midway through suspending but has no wake alarm. It will get stuck. We'd rather not remove the "move" since the idea is to avoid a cancelled suspend when the alarm fires _during_ suspend. It is difficult for the test to tell the difference between a suspend that was cancelled because the alarm fired too early and a suspend that was Signed-off-by: Bernie Thompson <bhthompson@chromium.org> Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Doug Anderson <dianders@chromium.org> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/rtc.txt')
-rw-r--r--Documentation/rtc.txt7
1 files changed, 4 insertions, 3 deletions
diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt
index 32aa4002de4a..596b60c08b74 100644
--- a/Documentation/rtc.txt
+++ b/Documentation/rtc.txt
@@ -153,9 +153,10 @@ since_epoch: The number of seconds since the epoch according to the RTC
time: RTC-provided time
wakealarm: The time at which the clock will generate a system wakeup
event. This is a one shot wakeup event, so must be reset
- after wake if a daily wakeup is required. Format is either
- seconds since the epoch or, if there's a leading +, seconds
- in the future.
+ after wake if a daily wakeup is required. Format is seconds since
+ the epoch by default, or if there's a leading +, seconds in the
+ future, or if there is a leading +=, seconds ahead of the current
+ alarm.
IOCTL INTERFACE
---------------