Re: GPIO control from ALSA

[Lars-Peter Clausen <lars@metafoo.de>]

On 04/20/2016 10:51 AM, Petr Kulhavy wrote:
> On 20.04.2016 10:33, Lars-Peter Clausen wrote:
>> On 04/20/2016 10:03 AM, Petr Kulhavy wrote:
>>> Hello,
>>>
>>> I'm writing a driver for ASoC "sound card" hardware which uses CPU GPIO to
>>> mute/unmute an analogue amplifier and another GPIO to control an analogue
>>> switch for line/mic switching. Is there an abstraction in ALSA to model this
>>> kind of hardware?
>> There is no abstraction. Use controls and/or DAPM and the standard GPIO API,
>> if you grep the sources you'll find a few examples of drivers using GPIOs to
>> mute amplifiers and similar (e.g. qi_lb60).
>>
>> - Lars
> 
> 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.

- Lars