This patch adds new clock type for the GPIO controller which can
timestamp gpio lines in using hardware means. To expose such
functionalities to the userspace, code has been added where
during line create or set config API calls, it checks for new
clock type and if requested, calls HTE API. During line change
event, the HTE subsystem pushes timestamp data to userspace
through gpiolib-cdev.

Signed-off-by: Dipen Patel <dipenp@nvidia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

GPL-2.0 license identifier is deprecated. User-space projects that want
to include the kernel header with their source-code will be unable to
become fully REUSE compliant due to the reuse tool complaining about
deprecated licenses. Change the SPDX identifier to GPL-2.0-only.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

The description of the flags field of the struct gpio_v2_line_info
mentions "the GPIO lines" while the info only applies to an individual
GPIO line.  This was accidentally changed from "the GPIO line" during
formatting improvements.

Reword to "this GPIO line" to clarify and to be consistent with other
struct gpio_v2_line_info fields.

Fixes: 2cc522d3931b ("gpio: uapi: kernel-doc formatting improvements")
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

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>

Clarify that a char array containing a string is considered 'empty' if
the first character is the null terminator. The remaining characters
are not relevant to this determination.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20201005070329.21055-6-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Remove leading whitespace in ABI v1 comment.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20201005070329.21055-5-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Add kernel-doc formatting to all references to structs, enums, fields
and constants, and move deprecation warnings into the Note section of
the deprecated struct.

Replace 'OR:ed' with 'added', as the former looks odd.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20201005070329.21055-4-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Make debounce_period_us field documentation consistent with other fields
in the union.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20201005070329.21055-3-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Fix kernel-doc warnings, specifically gpioline_info_changed.padding is
not documented and 'GPIO event types' describes defines, which are not
documented by kernel-doc.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20201005070329.21055-2-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Update uAPI documentation to deprecate v1 structs and ioctls.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>