linux-kernel - Re: [PATCH v5 1/2] dt-bindings: drm/bridge: MHDP8546 bridge binding changes for DSC

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Message-ID: <20250918-dandelion-guan-of-storm-fa2051@kuoka>
Date: Thu, 18 Sep 2025 10:30:20 +0900
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Harikrishna Shenoy <h-shenoy@...com>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org, 
	Laurent.pinchart@...asonboard.com, jonas@...boo.se, jernej.skrabec@...il.com, airlied@...il.com, 
	simona@...ll.ch, maarten.lankhorst@...ux.intel.com, mripard@...nel.org, 
	tzimmermann@...e.de, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	sjakhade@...ence.com, yamonkar@...ence.com, lumag@...nel.org, dianders@...omium.org, 
	jani.nikula@...el.com, luca.ceresoli@...tlin.com, andy.yan@...k-chips.com, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	devarsht@...com, u-kumar1@...com, s-jain1@...com, tomi.valkeinen@...asonboard.com
Subject: Re: [PATCH v5 1/2] dt-bindings: drm/bridge: MHDP8546 bridge binding
 changes for DSC

On Mon, Sep 15, 2025 at 04:00:40PM +0530, Harikrishna Shenoy wrote:
> From: Swapnil Jakhade <sjakhade@...ence.com>
> 
> Add binding changes for DSC(Display Stream Compression) in the MHDP8546
> DPI/DP bridge.
> 
> Signed-off-by: Swapnil Jakhade <sjakhade@...ence.com>
> Signed-off-by: Harikrishna Shenoy <h-shenoy@...com>
> ---
>  .../display/bridge/cdns,mhdp8546.yaml         | 24 ++++++++++++-------
>  1 file changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> index c2b369456e4e..2a05a7d5847f 100644
> --- a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> @@ -27,13 +27,12 @@ properties:
>            Register block for DSS_EDP0_INTG_CFG_VP registers in case of TI J7 SoCs.
>        - description:
>            Register block of mhdptx sapb registers.
> +      - description:
> +          Register block for mhdptx DSC encoder registers.
>  
>    reg-names:
> -    minItems: 1
> -    items:
> -      - const: mhdptx
> -      - const: j721e-intg
> -      - const: mhdptx-sapb
> +    description:
> +      Names corresponding to entries in the reg property.

No, top-level should have broadest constraints. In your case it is
min/maxItems.

Description is completely redundant. Wasn't here before, so why adding
it?

>  
>    clocks:
>      maxItems: 1
> @@ -100,18 +99,25 @@ allOf:
>        properties:
>          reg:
>            minItems: 2
> -          maxItems: 3
> +          maxItems: 4
>          reg-names:
>            minItems: 2
> -          maxItems: 3
> +          items:
> +            - const: mhdptx
> +            - const: j721e-intg
> +            - const: mhdptx-sapb
> +            - const: dsc
>      else:
>        properties:
>          reg:
>            minItems: 1
> -          maxItems: 2
> +          maxItems: 3
>          reg-names:
>            minItems: 1
> -          maxItems: 2
> +          items:
> +            - const: mhdptx
> +            - const: mhdptx-sapb

This is wrong. Previously CDNS variant had two items means it had
"j721e-intg". Now it's something else.

First, this is an ABI break.

Second, there is no explanation at all for it in the commit msg! Looks
like random change.

Read carefully writing-bindings doc.

Best regards,
Krzysztof