1What: /dev/rtcX 2Date: April 2005 3KernelVersion: 2.6.12 4Contact: linux-rtc@vger.kernel.org 5Description: 6 The ioctl interface to drivers for real-time clocks (RTCs). 7 Following actions are supported: 8 9 * RTC_RD_TIME, RTC_SET_TIME: Read or set the RTC time. Time 10 format is a Gregorian calendar date and 24 hour wall clock 11 time. 12 13 * RTC_AIE_ON, RTC_AIE_OFF: Enable or disable the alarm interrupt 14 for RTCs that support alarms 15 16 * RTC_ALM_READ, RTC_ALM_SET: Read or set the alarm time for 17 RTCs that support alarms. Can be set upto 24 hours in the 18 future. Requires a separate RTC_AIE_ON call to enable the 19 alarm interrupt. (Prefer to use RTC_WKALM_*) 20 21 * RTC_WKALM_RD, RTC_WKALM_SET: For RTCs that support a more 22 powerful interface, which can issue alarms beyond 24 hours and 23 enable IRQs in the same request. 24 25 * RTC_PIE_ON, RTC_PIE_OFF: Enable or disable the periodic 26 interrupt for RTCs that support periodic interrupts. 27 28 * RTC_UIE_ON, RTC_UIE_OFF: Enable or disable the update 29 interrupt for RTCs that support it. 30 31 * RTC_IRQP_READ, RTC_IRQP_SET: Read or set the frequency for 32 periodic interrupts for RTCs that support periodic interrupts. 33 Requires a separate RTC_PIE_ON call to enable the periodic 34 interrupts. 35 36 * RTC_VL_READ: Read the voltage inputs status of the RTC when 37 supported. The value is a bit field of RTC_VL_*, giving the 38 status of the main and backup voltages. 39 40 * RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs 41 need user interaction when the backup power provider is 42 replaced or charged to be able to clear the status. 43 44 The ioctl() calls supported by the older /dev/rtc interface are 45 also supported by the newer RTC class framework. However, 46 because the chips and systems are not standardized, some PC/AT 47 functionality might not be provided. And in the same way, some 48 newer features -- including those enabled by ACPI -- are exposed 49 by the RTC class framework, but can't be supported by the older 50 driver. 51