[alsa-devel] [PATCH v4 1/6] ASoC: core: add snd_soc_add_dai_pcm_controls helper

[Arnaud Pouliquen]

On 03/10/2016 06:06 AM, Vinod Koul wrote:
> On Tue, Mar 08, 2016 at 01:53:56PM +0100, Arnaud Pouliquen wrote:
>> Add helper function to register DAI controls that need to be 
>> linked to pcm device.
>> A list is handled in case controls are created before dai_link probe
> 
> Overall this patch looks good to us. But on first read it is not very clear
> how PCM and DAIs are inter related and why you need to do this. Since we are
> having similar issues we were able to quickly understand this, the
> suggestion would be to elborate a bit more in changelog.
Right, i will provide more details in commit message.
> 
> Second, why do we need a new API for this. Why not use existing asoc
> concepts and add one more field in dai_driver for dai_controls.
> Core can automagically create those controls and link to PCM.
Yes this was my first approach. Finally, i created a separate API, to be
able to support iec generic control in DAI ( patch 3/6 and 4/6).
These patches need possibility to attach private data to control.
If patches 3/6 and 4/6 are rejected, for sure i will rework it to use
existing API.
Today It is more on compromise than an optimized solution...
But, creating a generic iec control also implies a compatibility with
ASoC and none ASoC drivers...

> 
> Lastly, this doesn't help our usecase of DPCM where the HDMI codec is
> connected to a BE, so that rtd cannot be used and we need to link to FE, so
> not sure how we can solve that...
DPCM seems another story... I'm not fully up to date on DPCM concept,
but as i can remember no link between FE and BE except DAPM routing.
Perhaps, for DPCM, a solution should be to use index field for control,
instead of trying to dynamically link the codec control to PCM device?

Thanks
Arnaud