Re: [RFC/PATCHv2 2/4] arm: omap: gpio: implement set_debounce method

[Felipe Balbi <me@felipebalbi.com>]

On Thu, Apr 01, 2010 at 04:11:27PM +0300, Jani Nikula wrote:
> On Thu, Apr 1, 2010 at 12:32, Felipe Balbi <felipe.balbi@nokia.com> wrote:
> > On Thu, Apr 01, 2010 at 11:29:16AM +0200, ext Grazvydas Ignotas wrote:
> >>
> >> There is also an issue if somebody calls _set_gpio_debounce(bank, 1,
> >> 310) and _set_gpio_debounce(bank, 2, 620), the second call will
> >> override debounce setting of GPIO1 (as it's shared by the whole bank).
> >> This might be not what the user intended, would be useful to detect
> >> this and warn the user.
> >
> > good point. As this is RFC, I'll wait until everybody comments.
> 
> Hi Felipe -
> 
> You might want to have a look at [1] on irq debouncing. The hardware
> support for debouncing varies (bank/gpio restrictions, debounce
> timeouts, no support at all, what else?) so how can the users of this
> interface rely on debouncing? What are the guarantees? AFAICS e.g.
> gpio-keys would have to do software debouncing anyway.
> 
> [1] http://lkml.org/lkml/2008/9/24/325

I think we could provide a generic software debouncing mechanism, sure,
but if the hardware supports it, why not using ?

I believe Dave's approach is really good, this is just another way to do
it. The difference with this patch is that we have control over the
debouncing time.

-- 
balbi