--- /dev/null
+What: /sys/class/rtc/
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: linux-rtc@vger.kernel.org
+Description:
+ The rtc/ class subdirectory belongs to the RTC subsystem.
+
+What: /sys/class/rtc/rtcX/
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: linux-rtc@vger.kernel.org
+Description:
+ The /sys/class/rtc/rtc{0,1,2,3,...} directories correspond
+ to each RTC device.
+
+What: /sys/class/rtc/rtcX/date
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: linux-rtc@vger.kernel.org
+Description:
+ RTC-provided date in YYYY-MM-DD format
+
+What: /sys/class/rtc/rtcX/hctosys
+Date: September 2009
+KernelVersion: 2.6.32
+Contact: linux-rtc@vger.kernel.org
+Description:
+ 1 if the RTC provided the system time at boot via the
+ CONFIG_RTC_HCTOSYS kernel option, 0 otherwise
+
+What: /sys/class/rtc/rtcX/max_user_freq
+Date: October 2007
+KernelVersion: 2.6.24
+Contact: linux-rtc@vger.kernel.org
+Description:
+ The maximum interrupt rate an unprivileged user may request
+ from this RTC.
+
+What: /sys/class/rtc/rtcX/name
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: linux-rtc@vger.kernel.org
+Description:
+ The name of the RTC corresponding to this sysfs directory
+
+What: /sys/class/rtc/rtcX/since_epoch
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: linux-rtc@vger.kernel.org
+Description:
+ RTC-provided time as the number of seconds since the epoch
+
+What: /sys/class/rtc/rtcX/time
+Date: March 2006
+KernelVersion: 2.6.17
+Contact: linux-rtc@vger.kernel.org
+Description:
+ RTC-provided time in 24-hour notation (hh:mm:ss)
+
+What: /sys/class/rtc/rtcX/*/nvmem
+Date: February 2016
+KernelVersion: 4.6
+Contact: linux-rtc@vger.kernel.org
+Description:
+ The non volatile storage exported as a raw file, as described in
+ Documentation/nvmem/nvmem.txt
+
+What: /sys/class/rtc/rtcX/offset
+Date: February 2016
+KernelVersion: 4.6
+Contact: linux-rtc@vger.kernel.org
+Description:
+ 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.
+
+What: /sys/class/rtc/rtcX/wakealarm
+Date: February 2007
+KernelVersion: 2.6.20
+Contact: linux-rtc@vger.kernel.org
+Description:
+ 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 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.
the system clock from the discrete RTC, but use the integrated one for all
other tasks, because of its greater functionality.
-SYSFS interface
----------------
-
-The sysfs interface under /sys/class/rtc/rtcN provides access to various
-rtc attributes without requiring the use of ioctls. All dates and times
-are in the RTC's timezone, rather than in system time.
-
-================ ==============================================================
-date RTC-provided date
-hctosys 1 if the RTC provided the system time at boot via the
- CONFIG_RTC_HCTOSYS kernel option, 0 otherwise
-max_user_freq The maximum interrupt rate an unprivileged user may request
- from this RTC.
-name The name of the RTC corresponding to this sysfs directory
-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 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.
-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.
-*/nvmem The non volatile storage exported as a raw file, as described
- in Documentation/nvmem/nvmem.txt
-================ ==============================================================
-
IOCTL interface
---------------