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Subject[PATCH 02/17] rtc: Document RTC_VL_READ and RTC_VL_CLR ioctls
RTC_VL_READ and RTC_VL_CLR have been introduced in 2012 with commit
0f20b767e20a ("drivers/rtc/rtc-pcf8563.c: add RTC_VL_READ/RTC_VL_CLR ioctl

Document them now that they have been unified.

Signed-off-by: Alexandre Belloni <>
Documentation/ABI/testing/rtc-cdev | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/Documentation/ABI/testing/rtc-cdev b/Documentation/ABI/testing/rtc-cdev
index 97447283f13b..25910c3c3d7e 100644
--- a/Documentation/ABI/testing/rtc-cdev
+++ b/Documentation/ABI/testing/rtc-cdev
@@ -33,6 +33,14 @@ Description:
Requires a separate RTC_PIE_ON call to enable the periodic

+ * RTC_VL_READ: Read the voltage inputs status of the RTC when
+ supported. The value is a bit field of RTC_VL_*, giving the
+ status of the main and backup voltages.
+ * RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs
+ need user interaction when the backup power provider is
+ replaced or charged to be able to clear the status.
The ioctl() calls supported by the older /dev/rtc interface are
also supported by the newer RTC class framework. However,
because the chips and systems are not standardized, some PC/AT
 \ /
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