linux-kernel - Re: [PATCH 2/4] ASoC: dt-bindings: mediatek,mt8188-mt6359: Update DAI link node pattern

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Message-ID: <CAC=S1ni-F_oudNyskSbxS1s2gZG7m4U4+nLxt0=dt5+DDkhV4Q@mail.gmail.com>
Date: Mon, 28 Oct 2024 19:12:59 +0800
From: Fei Shao <fshao@...omium.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Mark Brown <broonie@...nel.org>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Conor Dooley <conor+dt@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Liam Girdwood <lgirdwood@...il.com>, Matthias Brugger <matthias.bgg@...il.com>, 
	Rob Herring <robh@...nel.org>, Trevor Wu <trevor.wu@...iatek.com>, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-mediatek@...ts.infradead.org, linux-sound@...r.kernel.org
Subject: Re: [PATCH 2/4] ASoC: dt-bindings: mediatek,mt8188-mt6359: Update DAI
 link node pattern

On Mon, Oct 28, 2024 at 4:56 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On Fri, Oct 25, 2024 at 06:44:42PM +0800, Fei Shao wrote:
> > The associated machine driver is not dependent on the format of DAI link
> > node names. This means we are allowed to use more descriptive names
> > instead of indices without impacting functionality.
> >
> > Update the binding to accept arbitrary DAI link names with a "-dai-link"
> > suffix. This is the common pattern used by the target (MT8188) and other
> > (MT8195, MT8186 etc.) MediaTek-based Chromebooks.
>
> We do not want arbitrary names. Why for example green-batman-dai-link
> should be correct? The existing pattern looks wrong. Please read DT spec
> and chapter about recommended names.

At first I was thinking about regex like
`^[a-z-]+(-[a-z]+)*-dai-link$` based on the DTS coding style guide,
but your example is not suggesting that.
and the name like "hs-capture-dai-link" was rejected, so it's not just
about enumerating the names either.
Or "^dai-link@[0-9a-f]+$"? But they don't tie to particular register
addresses... or just for some pseudo indices?
I could miss something about DAI links under the sound documentation.
Still trying to figure it out.

>
> >
> > Signed-off-by: Fei Shao <fshao@...omium.org>
> > ---
> >
> >  .../devicetree/bindings/sound/mediatek,mt8188-mt6359.yaml     | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/sound/mediatek,mt8188-mt6359.yaml b/Documentation/devicetree/bindings/sound/mediatek,mt8188-mt6359.yaml
> > index 701cedfa38d2..2da34b66818f 100644
> > --- a/Documentation/devicetree/bindings/sound/mediatek,mt8188-mt6359.yaml
> > +++ b/Documentation/devicetree/bindings/sound/mediatek,mt8188-mt6359.yaml
> > @@ -40,7 +40,7 @@ properties:
> >        name defined in the machine driver.
> >
> >  patternProperties:
> > -  "^dai-link-[0-9]+$":
> > +  ".*-dai-link$":
>
> This breaks existing users.

There's no existing users in upstream, and the only downstream user is
the MT8188 Chromebook DT that I'm trying to upstream, which I can fix.
This binding was upstreamed exclusively for that DT.
Even if we take a step back and assume someone has another DT already
following this pattern (and that would be a surprise), this wouldn't
break anything except a dtbs_check error, which would be trivial if
they don't run that or attempt upstreaming. The driver doesn't use
node names to distinguish DAI links.
I want to fix this pattern before any actual users are in the tree if
possible, but I'm also fine to stick with dai-link-0 to dai-link-10 in
the case that nothing is changed and the DT has to follow the existing
patterns.

Regards,
Fei

>
> >      type: object
> >      description:
> >        Container for dai-link level properties and CODEC sub-nodes.
> > @@ -112,7 +112,7 @@ examples:
> >              "Headphone", "Headphone L",
> >              "Headphone", "Headphone R",
> >              "AIN1", "Headset Mic";
> > -        dai-link-0 {
> > +        hdmi-dai-link {
>
> No. Not really justified.
>
> Best regards,
> Krzysztof
>