Re: [PATCH v11 20/21] dt-bindings: display: rockchip: dw-dp: Fix sound DAI cells

Hello Rob,

On Fri, Aug 07, 2026 at 10:51:40AM -0500, Rob Herring wrote:
> On Thu, Aug 06, 2026 at 05:39:59PM +0000, [email protected] wrote:
> > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> > - [Medium] Device Tree schema validation breakage for existing `rockchip,rk3588-dp` configurations.
> > --
> > 
> > --- Patch [20]: [PATCH v11 20/21] dt-bindings: display: rockchip: dw-dp: Fix sound DAI cells ---
> > commit 2c15bbfcf4dec184872abdf4c2e06063a52d1e2f
> > Author: Sebastian Reichel <[email protected]>
> > 
> > dt-bindings: display: rockchip: dw-dp: Fix sound DAI cells
> > 
> > The RK3588 and RK3576 DesignWare DisplayPort controllers both have two
> > possible DAI interfaces: I2S and S/PDIF. Thus an argument is needed to
> > to select the right interface.
> > 
> > > diff --git a/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml b/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml
> > > index 2b0d9e23e9432..c4f8959dd65da 100644
> > > --- a/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml
> > > +++ b/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml
> > [ ... ]
> > > @@ -83,7 +83,8 @@ properties:
> > >      maxItems: 1
> > >  
> > >    "#sound-dai-cells":
> > > -    const: 0
> > > +    const: 1
> > > +    description: 0 for I2S, 1 for S/PDIF
> > 
> > [Severity: Medium]
> > Will this strict constraint update cause make dtbs_check validation to
> > fail for existing in-tree device trees?
> > 
> > The mainline arch/arm64/boot/dts/rockchip/rk3588-base.dtsi still defines
> > #sound-dai-cells = <0>; for DP nodes.
> > 
> > While the commit message notes this breakage is intentional and will be
> > fixed up separately, could changing the schema without the accompanying
> > DTS updates cause automated CI validation failures and break bisectability?
> 
> Yes, and I don't love the intermittent warnings introduced. As long as 
> the warnings are on a downward trajectory, I won't notice...
> 
> Not saying you have to do something here, but this will get more 
> strict...

I don't like it either, but it's the best I came up with. If DT is
updated first, there will be a warning for the DAI cells being 1
instead of 0. To fully avoid the warning I see these options:

1. update DT binding and DTS in a single patch
2. allow 0 and 1 in the binding with 0 not really working

IMHO neither of those are great either, so I ended up with the
series like this. Regarding the downward trajectory: RK3588 should
be completley free of warnings in dtbs_check at the moment.

Greetings,

-- Sebastian

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