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RTC: Fix up rtc.txt documentation to reflect changes to generic rtc layer

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Now that the genric RTC layer handles much of the RTC functionality,
the rtc.txt documentation needs to be updated to remove outdated information.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Marcelo Roberto Jimenez <mroberto@cpti.cetuc.puc-rio.br>
CC: rtc-linux@googlegroups.com
Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
John Stultz 2011-02-10 15:32:59 -08:00
parent 416f0e8056
commit ea04683f59
1 changed files with 10 additions and 19 deletions
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29
Documentation/rtc.txt
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@ -178,38 +178,29 @@ RTC class framework, but can't be supported by the older driver.
setting the longer alarm time and enabling its IRQ using a single
request (using the same model as EFI firmware).
* RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, it probably
also offers update IRQs whenever the "seconds" counter changes.
If needed, the RTC framework can emulate this mechanism.
* RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, the RTC framework
will emulate this mechanism.
* RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... another
feature often accessible with an IRQ line is a periodic IRQ, issued
at settable frequencies (usually 2^N Hz).
* RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... these icotls
are emulated via a kernel hrtimer.
In many cases, the RTC alarm can be a system wake event, used to force
Linux out of a low power sleep state (or hibernation) back to a fully
operational state. For example, a system could enter a deep power saving
state until it's time to execute some scheduled tasks.
Note that many of these ioctls need not actually be implemented by your
driver. The common rtc-dev interface handles many of these nicely if your
driver returns ENOIOCTLCMD. Some common examples:
Note that many of these ioctls are handled by the common rtc-dev interface.
Some common examples:
* RTC_RD_TIME, RTC_SET_TIME: the read_time/set_time functions will be
called with appropriate values.
* RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: the
set_alarm/read_alarm functions will be called.
* RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: gets or sets
the alarm rtc_timer. May call the set_alarm driver function.
* RTC_IRQP_SET, RTC_IRQP_READ: the irq_set_freq function will be called
to set the frequency while the framework will handle the read for you
since the frequency is stored in the irq_freq member of the rtc_device
structure. Your driver needs to initialize the irq_freq member during
init. Make sure you check the requested frequency is in range of your
hardware in the irq_set_freq function. If it isn't, return -EINVAL. If
you cannot actually change the frequency, do not define irq_set_freq.
* RTC_IRQP_SET, RTC_IRQP_READ: These are emulated by the generic code.
* RTC_PIE_ON, RTC_PIE_OFF: the irq_set_state function will be called.
* RTC_PIE_ON, RTC_PIE_OFF: These are also emulated by the generic code.
If all else fails, check out the rtc-test.c driver!