gpiolib: cdev: allow edge event timestamps to be configured as REALTIME

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Using CLOCK_REALTIME as the source for event timestamps is crucial for
some specific applications, particularly those requiring timetamps
relative to a PTP clock, so provide an option to switch the event
timestamp source from the default CLOCK_MONOTONIC to CLOCK_REALTIME.

Note that CLOCK_REALTIME was the default source clock for GPIO until
Linux 5.7 when it was changed to CLOCK_MONOTONIC due to issues with the
shifting of the realtime clock.
Providing this option maintains the CLOCK_MONOTONIC as the default,
while also providing a path forward for those dependent on the pre-5.7
behaviour.

Suggested-by: Jack Winch <sunt.un.morcov@gmail.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20201014231158.34117-2-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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Kent Gibson 2020-10-15 07:11:56 +08:00 • committed by Linus Walleij

parent 93224edf0b

commit 26d060e47e

3 changed files with 28 additions and 6 deletions

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21

drivers/gpio/gpiolib-cdev.c

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1

drivers/gpio/gpiolib.h

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12

include/uapi/linux/gpio.h

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