linux-kernel - Re: [PATCH v2 01/12] dt-bindings: media: Convert MediaTek mt8173-mdp bindings to DT schema

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Message-ID: <969842f0-5113-40c1-b80d-d46bd239936a@kernel.org>
Date: Fri, 12 Sep 2025 15:25:18 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Chen-Yu Tsai <wenst@...omium.org>
Cc: Ariel D'Alessandro <ariel.dalessandro@...labora.com>, airlied@...il.com,
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Subject: Re: [PATCH v2 01/12] dt-bindings: media: Convert MediaTek mt8173-mdp
 bindings to DT schema

On 12/09/2025 10:27, Chen-Yu Tsai wrote:
>>> +properties:
>>> +  compatible:
>>> +    oneOf:
>>> +      - enum:
>>> +          - mediatek,mt8173-mdp-rdma
>>> +          - mediatek,mt8173-mdp-rsz
>>> +          - mediatek,mt8173-mdp-wdma
>>> +          - mediatek,mt8173-mdp-wrot
>>
>> Why there is no mediatek,mt8173-mdp here? What does this compatible
>> represent?
>>
>>> +      - items:
>>> +          - const: mediatek,mt8173-mdp-rdma
>>
>> Still suspicious. Device cannot be simulatanously: compatible and not
>> compatible. This is not a well known cat that has superposition of two
>> states, whenenver you look the other way.
>>
>> Maybe the old binding was incorrect, maybe the in-tree DTS is incorrect.
>> Whichever the reason, this must be investigated and documented, because
>> by standard rules this is wrong. Each wrong code needs very clear
>> explanations (and "someone did it" is not a good enough explanation).
> 
> My guess is that "mediatek,mt8173-mdp" is meant to serve as a single
> entry point for the implementation to bind the driver to. The MDP is

I am speaking about hardware. What piece of hardware it implements and
why sometimes it is RDMA MDP and sometimes it is not RDMA MDP, but only MDP.

> a Data Pipeline and there could be multiple instances of the same
> IP block, as seen in the original example.
> 
> The datasheet I have doesn't cover the "RDMA" block specifically, so
> I can't say whether there is an actual difference between the two RDMA
> blocks.
> 
> 
Best regards,
Krzysztof