diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt index 8deffcd..ac843ab 100644 --- a/Documentation/rtc.txt +++ b/Documentation/rtc.txt @@ -187,6 +187,88 @@ driver returns ENOIOCTLCMD. Some common If all else fails, check out the rtc-test.c driver! + Even newer /sys interface + ~~~~~~~~~~~~~~~~~~~~~~~~~ + +tino.keitel@xxxxxx + +How to use /sys/class/rtc/rtcX/wakealarm +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +This file takes the seconds since epoch to enable a wake event at the +specified time. + +If a '0' is written, the alarm is disabled. + +If the alarm was already enabled, a new alarm can only be set after the +old alarm is disabled. + + +Migration from /proc/acpi/alarm +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +Users of /proc/acpi/alarm have to change their code to supply the +seconds since epoch instead of a date string. + +For shell scripts, this can be done using the date command, e.g. like +this: + +date -d tomorrow "+%s" + +This returns the seconds since epoch of the current time on the +following day. + +Please note that you have to disable the old alarm first, if you want +to set a new alarm. Otherwise, you get an error. Example: + +echo 12345 > /sys/class/rtc/rtc0/wakealarm +echo 0 > /sys/class/rtc/rtc0/wakealarm +echo 23456 > /sys/class/rtc/rtc0/wakealarm + + +cd /proc/acpi +echo EXP0 > wakeup +echo PCI1 > wakeup +echo USB0 > wakeup +echo USB1 > wakeup +echo USB2 > wakeup +echo USB7 > wakeup +echo HDEF > wakeup +cd /sys/class/rtc/rtc0 +echo $(( $(cat since_epoch) + 20 )) > wakealarm + + [PATCH] RTC gets sysfs wakealarm attribute + + This adds a new "wakealarm" sysfs attribute to RTC class devices which support + alarm operations and are wakeup-capable: + + - It reads as either empty, or the scheduled alarm time as seconds + since the POSIX epoch. (That time may already have passed, since + nothing currently enforces one-shot alarm semantics.) + + - It can be written with an alarm time in the future, again seconds + since the POSIX epoch, which enables the alarm. + + - It can be written with an alarm time not in the future (such as 0, + the start of the POSIX epoch) to disable the alarm. + + Usage examples (some need GNU date) after "cd /sys/class/rtc/rtcN": + + alarm after 10 minutes: + # echo $(( $(cat since_epoch) + 10 * 60 )) > wakealarm + alarm tuesday evening 10pm: + # date -d '10pm tuesday' "+%s" > wakealarm + disable alarm: + # echo 0 > wakealarm + + This resembles the /proc/acpi/alarm file in that nothing happens when the + alarm triggers ... except possibly waking the system from sleep. It's also + like that in a nasty way: not much can be done to prevent one task from + clobbering another task's alarm settings. + + It differs from that file in that there's no in-kernel date parser. + + Note that a few RTCs ignore rtc_wkalrm.enabled when setting alarms, or aren't + set up correctly, so they won't yet behave with this attribute. + -------------------- 8< ---------------- 8< ----------------------------- -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
