[alsa-devel] [PATCH 1/9] ASoC: core: allow a dt node to provide several components

[Jerome Brunet]

On Thu 13 Feb 2020 at 18:18, Mark Brown <broonie at kernel.org> wrote:

> On Thu, Feb 13, 2020 at 04:51:51PM +0100, Jerome Brunet wrote:
>
>> At the moment, querying the dai_name will stop of the first component
>> matching the dt node. This does not allow a device (single dt node) to
>> provide several ASoC components which could then be used through DT.
>
>> This change let the search go on if the xlate function of the component
>> returns an error, giving the possibility to another component to match
>> and return the dai_name.
>
> My first question here would be why you'd want to do that rather than
> combine everything into a single component since the hardware seems to
> be doing that anyway.  Hopefully the rest of the series will answer this
> but it'd be good in the changelog here.

Hi Mark,

Sorry if I was not clear enough.

This HW is messy. It is indeed one monolithic device which
provides several functions/sub-devices/components

I tried several approaches:

* Just 1 component: This was ugly because the part that is present only on 1
SoC variant, I needed to reconstruct the dai, widget, route and control
table which involved a fair amount of useless copies.

* A lot of devices (and components) with syscon: This ended up being even
  uglier, difficult to work with since it did not really reflected the
  actual HW.

The solution proposed here is just one device with 3 possible
components (groups):
* The CPU producers a associated path
* The HDMI control
* The Internal DAC control

The impact on ASoC is rather small, the driver reflect quite well what
the HW is and, with a sound-dai-cell=2, it fairly simple in DT as well.

Do you think there is something wrong with a linux device providing
several ASoC components ?