[alsa-devel] dummy codec + simple card combination

[Belisko Marek]

On Tue, Mar 17, 2015 at 3:07 PM, Peter Ujfalusi <peter.ujfalusi at ti.com> wrote:
> On 03/13/2015 11:54 AM, Dr. H. Nikolaus Schaller wrote:
>>
>> For GSM there is some special logic for tri-stating a DAI because the
>> audio channel is wired to the twl4030 *and* a McBSP. This is for either
>> routing the voice directly to the twl or through the CPU (and some filters,
>> answering machine, sound scrambling etc.). This needs tri-state support
>> of the McBSP DX line.
>>
>>> Or write a custom machine driver and get it done ;)
>>
>> If you would find time (which is beyond what we can realistically expect) to look
>> into the non-DT 3.12 kernel where everything works, it would be here:
>>
>> http://git.goldelico.com/?p=gta04-kernel.git;a=tree;f=sound/soc/omap;hb=HEAD
>>
>> Basically we want to rebuild this using DT and use as much standard pieces
>> as possible. So that we only need to upstream what is missing for full gta04
>> support.
>
> I see. You have had written dummy codecs for the GSM, BT, the FM had an actual
> working driver.
>
> Hrm. There is one thing which would make sense for these audio devices:
> Since you do not have control over them in terms of formats, rates and
> protocol - they use fixed interfaces.
>
> I think it would make sense to have binding for something like:
> compatible = "fixed-codec" or something like that, implying that it's
> configuration can not be changed.
fixed-codec sounds good.
> In it's bindings you would have the supported properties of the interface,
> like rate, channels, sample width, protocol on the bus (I2S, DSP, etc) and to
> indicate if it is bus master or slave.
Instead of adding many properties to DT and parsing them cannot we
just hard code them
(rate, channels, width) in fixed-codec driver (similar as is done for
dummy-codec in soc-utils).
I'm not sure but how to use protocol on the bus and master/slave in
codec driver(must be used in glue card driver).
This fixed-codec driver could also cover e.g. spdif_receiver and
spdif_transmitter codecs which are also
only dummy.
>
> You could use this 'fixed-codec' to describe the DAIs and use simple-card to
> connect them with the CPU.
>
> I think this will fill in some gaps and it is actually going to describe the
> HW you have as well, so it is not Linux specific.
>

BR,

marek
>>
>>>
>>>> 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
>>
>> BR,
>> Nikolaus
>>
>
>
> --
> Péter



-- 
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