rtc: implement a sysfs interface for clock offset
clock offset may be set and read in decimal parts per billion
attribute is /sys/class/rtc/rtcN/offset
The attribute is only visible for rtcs that have set_offset implemented.
Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt
index 8446f1e..ddc3660 100644
--- a/Documentation/rtc.txt
+++ b/Documentation/rtc.txt
@@ -157,6 +157,12 @@
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.
+offset: The amount which the rtc clock has been adjusted in firmware.
+ Visible only if the driver supports clock offset adjustment.
+ The unit is parts per billion, i.e. The number of clock ticks
+ which are added to or removed from the rtc's base clock per
+ billion ticks. A positive value makes a day pass more slowly,
+ longer, and a negative value makes a day pass more quickly.
IOCTL INTERFACE
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