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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.
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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