linux-kernel - Re: [PATCH v4 12/23] ASoC: simple-card: Support DPCM DAI link with multiple Codecs

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Date:   Tue, 30 Jun 2020 09:38:22 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
CC:     <spujar@...dia.com>, <broonie@...nel.org>, <perex@...ex.cz>,
        <tiwai@...e.com>, <robh+dt@...nel.org>, <lgirdwood@...il.com>,
        <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <digetx@...il.com>, <alsa-devel@...a-project.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <sharadg@...dia.com>, <mkumard@...dia.com>,
        <viswanathl@...dia.com>, <rlokhande@...dia.com>,
        <dramesh@...dia.com>, <atalambedu@...dia.com>,
        <nwartikar@...dia.com>, <swarren@...dia.com>,
        <nicoleotsuka@...il.com>
Subject: Re: [PATCH v4 12/23] ASoC: simple-card: Support DPCM DAI link with
 multiple Codecs



On 6/30/2020 6:54 AM, Kuninori Morimoto wrote:
> External email: Use caution opening links or attachments
>
>
> Hi Sameer
>
>>> Maybe base issue for multiple codec support
>>> is that simple_for_each_link() is caring first codec only ?
> (snip)
>> Ideally I wanted to remove above two lines and allow empty codec
>> list. But some users may expect the parsing to fail if no 'Codec' is
>> found in the DAI link, hence did not remove above. If it is fine to
>> remove above two lines it would be simpler. The loop inside
>> simple_for_each_link() would anyway loop for each child node of DAI
>> link and simple_dai_link_of_dpcm() can parse each 'np'.

> Current simple-card is not assuming multi Codec,
> thus, we need to update it correctly, not quick-hack.
>
> I'm not sure how to do it, but it seems we need to update
> many functions to support it, not only simple-card driver.
> For example, simple-card-utils, soc-core, etc, etc...
>
> I'm not sure, this is just my guess.
> I'm happy if we can support it more easily :)
Right now I am trying re-use simple-card driver as much as possible and 
still make it work for flexible sound cards. I will be happy to discuss 
and improve the patch wherever necessary. Please help me understand 
which part you think looks to be hacky.

> But, if it was difficult to keep compatibility on simple-card,
> we/you need to have new one.
Patch 17/23 and 18/23 introduce new compatible 'simple-cc-audio-card'. 
Idea was to use component chaining which allows connection of FE<->BE 
and multiple BE<->BE components along the DAPM path (patch 16/23). Do 
you think it would be fine?

> Actually, I had a plan to create more flexible sound card
> driver, but it is not hi priority for me in these days.
>
> Thank you for your help !!
>
> Best regards
> ---
> Kuninori Morimoto