[alsa-devel] dummy codec + simple card combination

[Peter Ujfalusi]

Hi,

On 03/12/2015 08:33 PM, Belisko Marek wrote:
> Hi,
> 
> I posted same question on alsa-devel ML this week but I forgot to add
> sound omap + asoc maintainers (sorry about that)
> 
> I'm trying to add audio support for gta04 (for gsm + bt and fm audio).
> All audio sources are clock masters so basically connection is dummy
> codecs -> cpu dai (mcbsp ports).

The FM seams to be slave device (Si4705/Si4721) on the I2S bus.
But in any of the cases (FM, GSM and BT) how do you configure the DAI formats
of the 'codecs'? Si47xx has support for I2S, L_JUST and DSP mode for example.
What about the sample formats and rates?
I think there should be a driver for at least the FM. For BT there is a bt-sco
codec driver but w/o DT support.

> For implementing such thing I can see 2 options:
> 1. simple card driver which can easily describe cpu dai interface but
> dummy codec cannot because there are no DT bindings (there was sever
> attempts to add DT bindings for dummy-codec but AFAIK none was
> accepted)

Yes, the dummy-codec is Linux/ASoC concept and should not be described in DT.
However I think there should be a way to describing passive DAIs. Slave
devices only listening, or masters streaming the data.
But, I think even if you have such a device you do have some control, at least
to enable/disable them...

> This turns it to only solution to create gta04 soundcard which will
> get from DT cpu dai links and use in card driver dummy codecs
> directly.

I would look up the driver for the FM and write the codec driver for it,
probably the same can be done for the GSM and add bindings for the bt-sco so
all of this can work with simple-card.
Or write a custom machine driver and get it done ;)

> Is my assumption correct? I would like to get some feedback before
> wasting my time with implementing something which cannot be pushed
> mainline. Thanks for all suggestions.
> 
> BR,
> 
> marek
> 
> --
> as simple and primitive as possible
> -------------------------------------------------
> Marek Belisko - OPEN-NANDRA
> Freelance Developer
> 
> Ruska Nova Ves 219 | Presov, 08005 Slovak Republic
> Tel: +421 915 052 184
> skype: marekwhite
> twitter: #opennandra
> web: http://open-nandra.com
> 


-- 
Péter