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authorMatthew Garrett <mjg@redhat.com>2009-09-22 19:46:31 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 10:39:46 -0400
commitea3d1606fd32059461309099e8856c6652888a79 (patch)
tree5d70c39a7534801759a09c5e377afa8f04e7dcca /Documentation/rtc.txt
parentdac94d9ec98517e8fe3f980e38f29ea3ac712168 (diff)
rtc: document the sysfs interface
The sysfs interface to the RTC class drivers is currently undocumented. Add some basic documentation defining the semantics of the fields. Signed-off-by: Matthew Garrett <mjg@redhat.com> Cc: Mark Brown <broonie@opensource.wolfsonmicro.com> Acked-by: Alessandro Zummo <a.zummo@towertech.it> Cc: David Brownell <david-b@pacbell.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/rtc.txt')
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diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt
index 102ce9625e65..2745e8197fde 100644
--- a/Documentation/rtc.txt
+++ b/Documentation/rtc.txt
@@ -135,6 +135,28 @@ a high functionality RTC is integrated into the SOC. That system might read
135the system clock from the discrete RTC, but use the integrated one for all 135the system clock from the discrete RTC, but use the integrated one for all
136other tasks, because of its greater functionality. 136other tasks, because of its greater functionality.
137 137
138SYSFS INTERFACE
139---------------
140
141The sysfs interface under /sys/class/rtc/rtcN provides access to various
142rtc attributes without requiring the use of ioctls. All dates and times
143are in the RTC's timezone, rather than in system time.
144
145date: RTC-provided date
146max_user_freq: The maximum interrupt rate an unprivileged user may request
147 from this RTC.
148name: The name of the RTC corresponding to this sysfs directory
149since_epoch: The number of seconds since the epoch according to the RTC
150time: RTC-provided time
151wakealarm: The time at which the clock will generate a system wakeup
152 event. This is a one shot wakeup event, so must be reset
153 after wake if a daily wakeup is required. Format is either
154 seconds since the epoch or, if there's a leading +, seconds
155 in the future.
156
157IOCTL INTERFACE
158---------------
159
138The ioctl() calls supported by /dev/rtc are also supported by the RTC class 160The ioctl() calls supported by /dev/rtc are also supported by the RTC class
139framework. However, because the chips and systems are not standardized, 161framework. However, because the chips and systems are not standardized,
140some PC/AT functionality might not be provided. And in the same way, some 162some PC/AT functionality might not be provided. And in the same way, some