GPIO control from ALSA

GPIO control from ALSA

[Petr Kulhavy]

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?

Thanks
Petr

Re: GPIO control from ALSA

[Lars-Peter Clausen]

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

Re: GPIO control from ALSA

[Petr Kulhavy]

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.

Regards
Petr

Re: GPIO control from ALSA

[Lars-Peter Clausen]

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	

Re: GPIO control from ALSA

[Petr Kulhavy]

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?

Thanks
Petr

Re: GPIO control from ALSA

[Lars-Peter Clausen]

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.