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 The ioctl() calls supported by the older /dev/rtc interface are 37 also supported by the newer RTC class framework. However, 38 because the chips and systems are not standardized, some PC/AT 39 functionality might not be provided. And in the same way, some 40 newer features -- including those enabled by ACPI -- are exposed 41 by the RTC class framework, but can't be supported by the older 42 driver. 43