On Sat, Jun 26, 2021 at 1:48 AM Dipen Patel [off-list ref] wrote:

Some GPIO chip can provide hardware timestamp support on its GPIO lines
, in order to support that additional functions needs to be added which
can talk to both GPIO chip and HTE (hardware timestamping engine)
subsystem. This patch introduces functions which gpio consumer can use
to request hardware assisted timestamping. Below is the list of the APIs
that are added in gpiolib subsystem.

- gpiod_hw_timestamp_control - to enable/disable HTE on specified GPIO
line. This API will return HTE specific descriptor for the specified
GPIO line during the enable call, it will be stored as pointer in the
gpio_desc structure as hw_ts_data.
- gpiod_is_hw_timestamp_enabled - to query if HTE is enabled on
specified GPIO line.
- gpiod_get_hw_timestamp - to retrieve hardware timestamps.

Signed-off-by: Dipen Patel <dipenp@nvidia.com>

This looks good to me.

The chip driver can look up and provide a timestamp provider for a
certain line, which is proper since the GPIO hardware will be tightly
coupled with the timestamp hardware so we need to ask the hardware
about this directly and delegate it to the GPIO driver.

Yours,
Linus Walleij