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790a19f18a
RTC_VL_READ and RTC_VL_CLR have been introduced in 2012 with commit
0f20b767e2 ("drivers/rtc/rtc-pcf8563.c: add RTC_VL_READ/RTC_VL_CLR ioctl
feature")
Document them now that they have been unified.
Link: https://lore.kernel.org/r/20191214220259.621996-3-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
51 lines
2.0 KiB
Plaintext
51 lines
2.0 KiB
Plaintext
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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* RTC_VL_READ: Read the voltage inputs status of the RTC when
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supported. The value is a bit field of RTC_VL_*, giving the
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status of the main and backup voltages.
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* RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs
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need user interaction when the backup power provider is
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replaced or charged to be able to clear the status.
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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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