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