linux-kernel - Re: spitz: add gpio button support (AK_INT and remote control description)

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Date:	Wed, 07 Oct 2009 13:29:51 +0200
From:	Stanislav Brabec <utx@...guin.cz>
To:	Pavel Machek <pavel@....cz>
Cc:	rpurdie@...ys.net, lenz@...wisc.edu,
	kernel list <linux-kernel@...r.kernel.org>,
	Dirk@...er-Online.de, arminlitzel@....de,
	Cyril Hrubis <metan@....cz>, thommycheck@...il.com,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	dbaryshkov@...il.com, omegamoon@...il.com, eric.y.miao@...il.com,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: spitz: add gpio button support (AK_INT and remote control
 description)

Pavel Machek wrote:
> On Tue 2009-10-06 13:48:52, Stanislav Brabec wrote:
> > Pavel Machek wrote:
> > > I'm not sure what AK_INT is, nor what event it should
> > > generate.
> > 
> > AK_INT: remote control detect
> 
> Thanks. So for now I'll do:
> 
>         /* This is for remote control support. Zaurus supports wired                  
>            remote on headphones. */
>         {
>                 .type   = EV_KEY,
>                 .code   = KEY_F13,
>                 .gpio   = SPITZ_GPIO_AK_INT,
>                 .desc   = "Wired remote (AK_INT)",
>         },
> 
> ..and leave it for proper driver to support nicely.

I think that AK_INT should not generate key press event. Permanently
pressed key could confuse many programs.

But we may want to use switch events. I propose to create new switch
event for it: SW_REMOTE_INSERT. But mapping of AK_INT to
SW_REMOTE_INSERT cannot be straightforward.

That is why I propose to ignore AK_INT for now.

Following implementation may be used later (with future resistor matrix
keyboard driver):

Map SPITZ_GPIO_HP_IN to SW_JACK_PHYSICAL_INSERT (after debouncing).

Generate SW_REMOTE_INSERT if:
- SW_JACK_PHYSICAL_INSERT is on AK_INT is active and remote pin has full
  voltage
or
- SW_JACK_PHYSICAL_INSERT is on and remote driver shows valid value

SW_REMOTE_INSERT should be recognized by the Jack abstraction layer
(sound/core/jack.c).

Well, I am thinking about defining extra values for resistors, that can
make stuff even more useful at cost of need of non-standard wiring on
fourth ring of the audio jack. It can generate SW_MICROPHONE_INSERT,
SW_LINEOUT_INSERT, and not yet defined SW_HEADESET_INSERT and
SW_LINEIN_INSERT (which would require hardware mod inside Zaurus for
stereo line-in).

The default may be SW_HEADPHONE_INSERT (short connection between remote
pin and ground).

-- 
Best Regards / S pozdravem,

Stanislav Brabec
software developer
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