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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the rtc.txt documentation needs to be updated to remove outdated information.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 setting the longer alarm time and enabling its IRQ using a single
request (using the same model as EFI firmware). request (using the same model as EFI firmware).
* RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, it probably * RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, the RTC framework
also offers update IRQs whenever the "seconds" counter changes. will emulate this mechanism.
If needed, the RTC framework can emulate this mechanism.
* RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... another * RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... these icotls
feature often accessible with an IRQ line is a periodic IRQ, issued are emulated via a kernel hrtimer.
at settable frequencies (usually 2^N Hz).
In many cases, the RTC alarm can be a system wake event, used to force 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 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 operational state. For example, a system could enter a deep power saving
state until it's time to execute some scheduled tasks. state until it's time to execute some scheduled tasks.
Note that many of these ioctls need not actually be implemented by your Note that many of these ioctls are handled by the common rtc-dev interface.
driver. The common rtc-dev interface handles many of these nicely if your Some common examples:
driver returns ENOIOCTLCMD. Some common examples:
* RTC_RD_TIME, RTC_SET_TIME: the read_time/set_time functions will be * RTC_RD_TIME, RTC_SET_TIME: the read_time/set_time functions will be
called with appropriate values. called with appropriate values.
* RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: the * RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: gets or sets
set_alarm/read_alarm functions will be called. 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 * RTC_IRQP_SET, RTC_IRQP_READ: These are emulated by the generic code.
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_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! If all else fails, check out the rtc-test.c driver!