[alsa-devel] [PATCH] ASoC: Jack: add configurable option for irq_flag

[Omair M. Abdullah]

On Fri, Feb 15, 2013 at 12:17:27PM +0000, Mark Brown wrote:
> On Fri, Feb 15, 2013 at 12:40:00PM +0530, Omair M. Abdullah wrote:
> 
> > This patch is mainly to handle GPIOs where there is some toggling of the GPIO
> > lines due to the switch bouncing, and the debounce time cannot be increased
> > further due to other constraints. In such cases, providing the specific
> > edge on which to trigger the interrupt helps increase the robustness.
> 
> >      ___   _                _   _________
> > e.g.    |_| |______________| |_|
> 
> > insert followed by removal, where we want to trigger on the falling edge in both
> > cases.
> 
> This doesn't make much sense to me, it's a *very* non-obvious change and
> it doesn't reflect what's actually happening well.  If you happen to be
> lucky and get no bounce it'll fail.  If it's working on your system
> there is a fair element of luck in there.
> 
> It sounds like all you're looking for here is a better debounce
> algorithm, for example one that delays for a bit then starts polling the
> GPIO state at a higher rate and declares a result when the GPIO state
> doesn't change for a few polls.
We are using a polling mechanism in our system to check the jack state a few
times. But what we observed is that we always get a bounce.

Also, we do have a system where we are using the snd_soc_jack_gpio code for a
codec interrupt through a GPIO line, like Ramesh mentioned - even if it is just
for re-using the software debounce mechanism. In such cases, the interrupt would
be triggered on one edge only. Maybe that is not the original intent the of that
code?