[PATCH] ASoC: snd-soc-dummy: add Device Tree support

[Judy Hsiao]

On Mon, Jun 21, 2021 at 7:46 PM Mark Brown <broonie at kernel.org> wrote:
>
> On Mon, Jun 21, 2021 at 03:41:52PM +0800, Judy Hsiao wrote:
>
> > Support for loading the snd-soc-dummy via DeviceTree.
> > This is useful to create dummy codec devices where we need to have some
> > DAI links without a real Codec.
>
> Why would it be useful to create DAI links to a dummy device that has
> no properties?  If you've got a device with no software control it's
> still going to have some limits on things like what formats and sample
> rates it can accept so you should describe that in DT.

Thanks for your review comment.
This patch is used to support multi-channel where we want one codec to
control the only GPIO shared by 4 amps.
(Please refer to
:https://patchwork.kernel.org/project/alsa-devel/patch/20210526154704.114957-1-judyhsiao@chromium.org/)

In snd_soc_runtime_calc_hw(), by creating dummy codecs that share a
DAI link with a real codec:
  1. The min/ max channel of  CPU DAI will be directly adopted.
  2. The formats and sample rates of the DAI link will be determined
by the real codec unless the real codec supports the rate
      and format that do not intersect with the rate and format of
snd-soc-dummy.
That is the reason why we don’t specify the format and sample rates of
the dummy codec with the real codec determining the properties .

Does reposting a new patch with  a more clear commit message to
describe the use case sound good to you?
>
> Please try to keep the CC lists for patches you are submitting relevant
> to the patch, people get a lot of mail and reviews for irrelevant
> patches add to the noise.
Sorry about that. I have adjusted the CC lists.