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 36*790a19f1SAlexandre Belloni * RTC_VL_READ: Read the voltage inputs status of the RTC when 37*790a19f1SAlexandre Belloni supported. The value is a bit field of RTC_VL_*, giving the 38*790a19f1SAlexandre Belloni status of the main and backup voltages. 39*790a19f1SAlexandre Belloni 40*790a19f1SAlexandre Belloni * RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs 41*790a19f1SAlexandre Belloni need user interaction when the backup power provider is 42*790a19f1SAlexandre Belloni replaced or charged to be able to clear the status. 43*790a19f1SAlexandre 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. 51