Re: [PATCH] gpiolib: add GPIO_SET_DEBOUNCE_IOCTL

[Linus Walleij]

On Wed, Apr 29, 2020 at 2:06 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:

> I understand the need to set debounce time to make line events
> reliable. As I see it: there'll be a couple steps to add this.

I think there is a serious user-facing problem here though, because
not all GPIO controllers supports debounce, so the call may return
"nope" (error code).

I think that is unavoidable with things like pull-up/down or drive
strength, but for debounce I think we could do better.
drivers/input/keyboard/gpio_keys.c contains generic
debounce code using kernel timers if the GPIO driver
cannot provide debouncing, and I have thought for a long
time that it would be nice if we could do this generic, so that
we always provide debouncing if requested, even for in-kernel
consumers but most certainly for userspace consumers,
else userspace will just start to reinvent this too.

Yours,
Linus Walleij