162306a36Sopenharmony_ciWhat:		/dev/rtcX
262306a36Sopenharmony_ciDate:		April 2005
362306a36Sopenharmony_ciKernelVersion:	2.6.12
462306a36Sopenharmony_ciContact:	linux-rtc@vger.kernel.org
562306a36Sopenharmony_ciDescription:
662306a36Sopenharmony_ci		The ioctl interface to drivers for real-time clocks (RTCs).
762306a36Sopenharmony_ci		Following actions are supported:
862306a36Sopenharmony_ci
962306a36Sopenharmony_ci		* RTC_RD_TIME, RTC_SET_TIME: Read or set the RTC time. Time
1062306a36Sopenharmony_ci		  format is a Gregorian calendar date and 24 hour wall clock
1162306a36Sopenharmony_ci		  time.
1262306a36Sopenharmony_ci
1362306a36Sopenharmony_ci		* RTC_AIE_ON, RTC_AIE_OFF: Enable or disable the alarm interrupt
1462306a36Sopenharmony_ci		  for RTCs that support alarms
1562306a36Sopenharmony_ci
1662306a36Sopenharmony_ci		* RTC_ALM_READ, RTC_ALM_SET: Read or set the alarm time for
1762306a36Sopenharmony_ci		  RTCs that support alarms. Can be set upto 24 hours in the
1862306a36Sopenharmony_ci		  future. Requires a separate RTC_AIE_ON call to enable the
1962306a36Sopenharmony_ci		  alarm interrupt. (Prefer to use RTC_WKALM_*)
2062306a36Sopenharmony_ci
2162306a36Sopenharmony_ci		* RTC_WKALM_RD, RTC_WKALM_SET: For RTCs that support a more
2262306a36Sopenharmony_ci		  powerful interface, which can issue alarms beyond 24 hours and
2362306a36Sopenharmony_ci		  enable IRQs in the same request.
2462306a36Sopenharmony_ci
2562306a36Sopenharmony_ci		* RTC_PIE_ON, RTC_PIE_OFF: Enable or disable the periodic
2662306a36Sopenharmony_ci		  interrupt for RTCs that support periodic interrupts.
2762306a36Sopenharmony_ci
2862306a36Sopenharmony_ci		* RTC_UIE_ON, RTC_UIE_OFF: Enable or disable the update
2962306a36Sopenharmony_ci		  interrupt for RTCs that support it.
3062306a36Sopenharmony_ci
3162306a36Sopenharmony_ci		* RTC_IRQP_READ, RTC_IRQP_SET: Read or set the frequency for
3262306a36Sopenharmony_ci		  periodic interrupts for RTCs that support periodic interrupts.
3362306a36Sopenharmony_ci		  Requires a separate RTC_PIE_ON call to enable the periodic
3462306a36Sopenharmony_ci		  interrupts.
3562306a36Sopenharmony_ci
3662306a36Sopenharmony_ci		* RTC_VL_READ: Read the voltage inputs status of the RTC when
3762306a36Sopenharmony_ci		  supported. The value is a bit field of RTC_VL_*, giving the
3862306a36Sopenharmony_ci		  status of the main and backup voltages.
3962306a36Sopenharmony_ci
4062306a36Sopenharmony_ci		* RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs
4162306a36Sopenharmony_ci		  need user interaction when the backup power provider is
4262306a36Sopenharmony_ci		  replaced or charged to be able to clear the status.
4362306a36Sopenharmony_ci
4462306a36Sopenharmony_ci		The ioctl() calls supported by the older /dev/rtc interface are
4562306a36Sopenharmony_ci		also supported by the newer RTC class framework. However,
4662306a36Sopenharmony_ci		because the chips and systems are not standardized, some PC/AT
4762306a36Sopenharmony_ci		functionality might not be provided. And in the same way, some
4862306a36Sopenharmony_ci		newer features -- including those enabled by ACPI -- are exposed
4962306a36Sopenharmony_ci		by the RTC class framework, but can't be supported by the older
5062306a36Sopenharmony_ci		driver.
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