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:
		(RO) 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:
		(RO) 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:
		(RW) 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:
		(RO) 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:
		(RO) 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:
		(RO) 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:
		(RW) 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:
		(RW) 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:
		(RW) 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.
