From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lars-Peter Clausen <lars@metafoo.de>
Subject: Re: GPIO control from ALSA
Date: Wed, 20 Apr 2016 12:39:39 +0200
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To: Petr Kulhavy <petr@barix.com>, alsa-devel@alsa-project.org
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On 04/20/2016 11:47 AM, Petr Kulhavy wrote:
> 
> 
> On 20.04.2016 11:06, Lars-Peter Clausen wrote:
>> On 04/20/2016 10:51 AM, Petr Kulhavy wrote:
>>>
>>> Thanks, Lars, for the good pointers! I will check that out.
>>>
>>> Is there also a way to map GPIO to a control which then appears e.g. in
>>> alsamixer? That would be useful for the mic/line selection.
>> Rather than exposing the GPIO itself you'd expose the logical function of
>> the GPIO. E.g. in your case a ENUM control that allows to switch between
>> microphone and capture and in the background this sets the GPIO according to
>> the selection.
> 
> I understand that, my question was more how to hook the enum to a function
> rather to a codec register?

You can use SOC_ENUM_EXT() to create the control. This macro takes a get and
a put callback where you can manipulate the state of the GPIO. And then just
register the control with the card.