1*4882a593SmuzhiyunWhat: /dev/rtcX 2*4882a593SmuzhiyunDate: April 2005 3*4882a593SmuzhiyunKernelVersion: 2.6.12 4*4882a593SmuzhiyunContact: linux-rtc@vger.kernel.org 5*4882a593SmuzhiyunDescription: 6*4882a593Smuzhiyun The ioctl interface to drivers for real-time clocks (RTCs). 7*4882a593Smuzhiyun Following actions are supported: 8*4882a593Smuzhiyun 9*4882a593Smuzhiyun * RTC_RD_TIME, RTC_SET_TIME: Read or set the RTC time. Time 10*4882a593Smuzhiyun format is a Gregorian calendar date and 24 hour wall clock 11*4882a593Smuzhiyun time. 12*4882a593Smuzhiyun 13*4882a593Smuzhiyun * RTC_AIE_ON, RTC_AIE_OFF: Enable or disable the alarm interrupt 14*4882a593Smuzhiyun for RTCs that support alarms 15*4882a593Smuzhiyun 16*4882a593Smuzhiyun * RTC_ALM_READ, RTC_ALM_SET: Read or set the alarm time for 17*4882a593Smuzhiyun RTCs that support alarms. Can be set upto 24 hours in the 18*4882a593Smuzhiyun future. Requires a separate RTC_AIE_ON call to enable the 19*4882a593Smuzhiyun alarm interrupt. (Prefer to use RTC_WKALM_*) 20*4882a593Smuzhiyun 21*4882a593Smuzhiyun * RTC_WKALM_RD, RTC_WKALM_SET: For RTCs that support a more 22*4882a593Smuzhiyun powerful interface, which can issue alarms beyond 24 hours and 23*4882a593Smuzhiyun enable IRQs in the same request. 24*4882a593Smuzhiyun 25*4882a593Smuzhiyun * RTC_PIE_ON, RTC_PIE_OFF: Enable or disable the periodic 26*4882a593Smuzhiyun interrupt for RTCs that support periodic interrupts. 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun * RTC_UIE_ON, RTC_UIE_OFF: Enable or disable the update 29*4882a593Smuzhiyun interrupt for RTCs that support it. 30*4882a593Smuzhiyun 31*4882a593Smuzhiyun * RTC_IRQP_READ, RTC_IRQP_SET: Read or set the frequency for 32*4882a593Smuzhiyun periodic interrupts for RTCs that support periodic interrupts. 33*4882a593Smuzhiyun Requires a separate RTC_PIE_ON call to enable the periodic 34*4882a593Smuzhiyun interrupts. 35*4882a593Smuzhiyun 36*4882a593Smuzhiyun * RTC_VL_READ: Read the voltage inputs status of the RTC when 37*4882a593Smuzhiyun supported. The value is a bit field of RTC_VL_*, giving the 38*4882a593Smuzhiyun status of the main and backup voltages. 39*4882a593Smuzhiyun 40*4882a593Smuzhiyun * RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs 41*4882a593Smuzhiyun need user interaction when the backup power provider is 42*4882a593Smuzhiyun replaced or charged to be able to clear the status. 43*4882a593Smuzhiyun 44*4882a593Smuzhiyun The ioctl() calls supported by the older /dev/rtc interface are 45*4882a593Smuzhiyun also supported by the newer RTC class framework. However, 46*4882a593Smuzhiyun because the chips and systems are not standardized, some PC/AT 47*4882a593Smuzhiyun functionality might not be provided. And in the same way, some 48*4882a593Smuzhiyun newer features -- including those enabled by ACPI -- are exposed 49*4882a593Smuzhiyun by the RTC class framework, but can't be supported by the older 50*4882a593Smuzhiyun driver. 51