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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.
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