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SubjectRe: [PATCH] rtc: sysfs: move sysfs & ioctl interface to Documentation/ABI
Hi,

Well, I had that patch:
https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git/commit/?h=rtc-ranges&id=79729c30854986faf4d26b0303dba220f4ef89de
part of a series I didn't send yet (it is still WIP and I just pushed
it).

Can you rebase on top of that? The RO/RW annotation would be a nice
addition.

Please, move the ioctl documentation to its own file,
Documentation/ABI/stable/rtc-cdev

On 01/01/2018 at 17:27:26 +0530, Aishwarya Pant wrote:
> +IOCTL interface
> +---------------
> +
> +What: /dev/rtc[0-*]

The [0-*] range is not correct, it should be [0-9]+

> +Date: April 2005
> +KernelVersion: 2.6.12
> +Contact: Alexandre Belloni <alexandre.belloni@free-electrons.com>

This must be the RTC mailing list.

> +Description: The ioctl() calls supported by /dev/rtc are also supported by
> + the 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.
> +

Out of context, this paragraph is weird.

> + * RTC_RD_TIME, RTC_SET_TIME ... every RTC supports at
> + least reading time, returning the result as a Gregorian
> + calendar date and 24 hour wall clock time. To be most
> + useful, this time may also be updated.
> +
> + * RTC_AIE_ON, RTC_AIE_OFF, RTC_ALM_SET, RTC_ALM_READ ...
> + when the RTC is connected to an IRQ line, it can often
> + issue an alarm IRQ up to 24 hours in the future. (Use
> + RTC_WKALM_* by preference.)
> +
> + * RTC_WKALM_SET, RTC_WKALM_RD ... RTCs that can issue
> + alarms beyond the next 24 hours use a slightly more
> + powerful API, which supports 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, the
> + RTC framework will emulate this mechanism.
> +
> + * 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 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:
> + gets or sets the alarm rtc_timer. May call the set_alarm
> + driver function.
> +
> + * RTC_IRQP_SET, RTC_IRQP_READ: These are emulated by the
> + generic code.
> +
> + * RTC_PIE_ON, RTC_PIE_OFF: These are also emulated by the
> + generic code.
> +
> + If all else fails, check out the
> + tools/testing/selftests/timers/rtctest.c test!

The reference to this test should probably stay in rtc.txt

--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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