[alsa-devel] [PATCH] ALSA: SoC: Added jack detection kcontrol support

[Mark Brown]

On Tue, Jul 23, 2013 at 05:10:29PM -0700, Felipe Tonello wrote:
> On Tue, Jul 23, 2013 at 5:40 AM, Mark Brown <broonie at kernel.org> wrote:

> > This was the existing kernel API at the time that the code was added -
> > I beleive people had been doing that for simple switches that detect the
> > physical presence of a jack since it looks exactly like a button from a
> > hardware point of view.  See the original commit adding the code.

> I saw it. I don't know what you think is the best way to go. I'm not
> sure if someone is using this input event API, since even PulseAudio
> even declined that implementation due KControl implementation.

It's used quite a bit in embedded systems, there are actually patches
for PulseAudio which were deployed for a while - I guess they might have
been removed or something.  The kcontrol stuff was actually implemented
after that was already in place.

> I'm thinking in re-implement core/jack.c using only kcontrol for
> reporting status and leaving input events only for keys (which is
> already implemented). This will break compatibility if any user-space
> checks for jack status using input events, but again, is anyone using
> this?

The jack core should be implementing all three methods of reporting
jacks (input, controls and extcon).
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