On Mon, May 4, 2020 at 12:32 PM Bartosz Golaszewski [off-list ref] wrote:

Ideally we'd have to introduce new versions of gpioevent_request,
gpioline_request, gpioline_info and gpioevent_data structs - this time
with enough additional padding and no alignment issues. Then we could
add the debounce properly.

Hm that sounds massive. Is it really that bad?

This would of course add a lot of cruft to the uAPI code. I'd start by
moving it out of drivers/gpio/gpiolib.c into a new file:
drivers/gpio/gpiolib-cdev.c. This way we'd have everything related to
the character device in one place. It would make it easier to: a) add
a config option for disabling it entirely and b) add a config option
to disable the v1 of the ioctl()s.

Its good to break out for code maintenance no matter what we do
with it :)

I would however not make it in any way totally optional, because the
big win with the character device over the legacy sysfs is to always
be available.

Linus: about the software-debounce you mentioned: do you think it
somehow plugs the hole we identified here?

Hm, I don't quite understand what the hole is I guess...

Linus