| What: /dev/rtcX |
| Date: April 2005 |
| KernelVersion: 2.6.12 |
| Contact: linux-rtc@vger.kernel.org |
| Description: |
| The ioctl interface to drivers for real-time clocks (RTCs). |
| Following actions are supported: |
| |
| * RTC_RD_TIME, RTC_SET_TIME: Read or set the RTC time. Time |
| format is a Gregorian calendar date and 24 hour wall clock |
| time. |
| |
| * RTC_AIE_ON, RTC_AIE_OFF: Enable or disable the alarm interrupt |
| for RTCs that support alarms |
| |
| * RTC_ALM_READ, RTC_ALM_SET: Read or set the alarm time for |
| RTCs that support alarms. Can be set upto 24 hours in the |
| future. Requires a separate RTC_AIE_ON call to enable the |
| alarm interrupt. (Prefer to use RTC_WKALM_*) |
| |
| * RTC_WKALM_RD, RTC_WKALM_SET: For RTCs that support a more |
| powerful interface, which can issue alarms beyond 24 hours and |
| enable IRQs in the same request. |
| |
| * RTC_PIE_ON, RTC_PIE_OFF: Enable or disable the periodic |
| interrupt for RTCs that support periodic interrupts. |
| |
| * RTC_UIE_ON, RTC_UIE_OFF: Enable or disable the update |
| interrupt for RTCs that support it. |
| |
| * RTC_IRQP_READ, RTC_IRQP_SET: Read or set the frequency for |
| periodic interrupts for RTCs that support periodic interrupts. |
| Requires a separate RTC_PIE_ON call to enable the periodic |
| interrupts. |
| |
| * RTC_VL_READ: Read the voltage inputs status of the RTC when |
| supported. The value is a bit field of RTC_VL_*, giving the |
| status of the main and backup voltages. |
| |
| * RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs |
| need user interaction when the backup power provider is |
| replaced or charged to be able to clear the status. |
| |
| The ioctl() calls supported by the older /dev/rtc interface are |
| also supported by the newer RTC class framework. However, |
| because the chips and systems are not standardized, some PC/AT |
| functionality might not be provided. And in the same way, some |
| newer features -- including those enabled by ACPI -- are exposed |
| by the RTC class framework, but can't be supported by the older |
| driver. |
