Re: [PATCH] gpiolib: add GPIO_SET_DEBOUNCE_IOCTL

[Bartosz Golaszewski]

År., 29 kwi 2020 o 14:38 Linus Walleij <linus.walleij@xxxxxxxxxx> napisaÅ(a):
>
> 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.

For bias we don't return an error if the operation is not supported by
the driver.

> 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.
>

Thanks for bringing this to my attention. This definitely looks like
something we could pull into gpiolib for others to use.

Bart