1796c0ad7SAishwarya PantWhat:		/dev/rtcX
2796c0ad7SAishwarya PantDate:		April 2005
3796c0ad7SAishwarya PantKernelVersion:	2.6.12
4796c0ad7SAishwarya PantContact:	linux-rtc@vger.kernel.org
5796c0ad7SAishwarya PantDescription:
6796c0ad7SAishwarya Pant		The ioctl interface to drivers for real-time clocks (RTCs).
7796c0ad7SAishwarya Pant		Following actions are supported:
8796c0ad7SAishwarya Pant
9796c0ad7SAishwarya Pant		* RTC_RD_TIME, RTC_SET_TIME: Read or set the RTC time. Time
10796c0ad7SAishwarya Pant		  format is a Gregorian calendar date and 24 hour wall clock
11796c0ad7SAishwarya Pant		  time.
12796c0ad7SAishwarya Pant
13796c0ad7SAishwarya Pant		* RTC_AIE_ON, RTC_AIE_OFF: Enable or disable the alarm interrupt
14796c0ad7SAishwarya Pant		  for RTCs that support alarms
15796c0ad7SAishwarya Pant
16796c0ad7SAishwarya Pant		* RTC_ALM_READ, RTC_ALM_SET: Read or set the alarm time for
17796c0ad7SAishwarya Pant		  RTCs that support alarms. Can be set upto 24 hours in the
18796c0ad7SAishwarya Pant		  future. Requires a separate RTC_AIE_ON call to enable the
19796c0ad7SAishwarya Pant		  alarm interrupt. (Prefer to use RTC_WKALM_*)
20796c0ad7SAishwarya Pant
21796c0ad7SAishwarya Pant		* RTC_WKALM_RD, RTC_WKALM_SET: For RTCs that support a more
22796c0ad7SAishwarya Pant		  powerful interface, which can issue alarms beyond 24 hours and
23796c0ad7SAishwarya Pant		  enable IRQs in the same request.
24796c0ad7SAishwarya Pant
25796c0ad7SAishwarya Pant		* RTC_PIE_ON, RTC_PIE_OFF: Enable or disable the periodic
26796c0ad7SAishwarya Pant		  interrupt for RTCs that support periodic interrupts.
27796c0ad7SAishwarya Pant
28796c0ad7SAishwarya Pant		* RTC_UIE_ON, RTC_UIE_OFF: Enable or disable the update
29796c0ad7SAishwarya Pant		  interrupt for RTCs that support it.
30796c0ad7SAishwarya Pant
31796c0ad7SAishwarya Pant		* RTC_IRQP_READ, RTC_IRQP_SET: Read or set the frequency for
32796c0ad7SAishwarya Pant		  periodic interrupts for RTCs that support periodic interrupts.
33796c0ad7SAishwarya Pant		  Requires a separate RTC_PIE_ON call to enable the periodic
34796c0ad7SAishwarya Pant		  interrupts.
35796c0ad7SAishwarya Pant
36790a19f1SAlexandre Belloni		* RTC_VL_READ: Read the voltage inputs status of the RTC when
37790a19f1SAlexandre Belloni		  supported. The value is a bit field of RTC_VL_*, giving the
38790a19f1SAlexandre Belloni		  status of the main and backup voltages.
39790a19f1SAlexandre Belloni
40790a19f1SAlexandre Belloni		* RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs
41790a19f1SAlexandre Belloni		  need user interaction when the backup power provider is
42790a19f1SAlexandre Belloni		  replaced or charged to be able to clear the status.
43790a19f1SAlexandre Belloni
44796c0ad7SAishwarya Pant		The ioctl() calls supported by the older /dev/rtc interface are
45796c0ad7SAishwarya Pant		also supported by the newer RTC class framework. However,
46796c0ad7SAishwarya Pant		because the chips and systems are not standardized, some PC/AT
47796c0ad7SAishwarya Pant		functionality might not be provided. And in the same way, some
48796c0ad7SAishwarya Pant		newer features -- including those enabled by ACPI -- are exposed
49796c0ad7SAishwarya Pant		by the RTC class framework, but can't be supported by the older
50796c0ad7SAishwarya Pant		driver.
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