linux-kernel - Re: [PATCH v3 2/9] dt-bindings: display: add verisilicon,dc

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Message-ID: <b68f333c-ccf5-4ecb-9d99-05d0f6e36391@kernel.org>
Date: Thu, 27 Nov 2025 14:58:54 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Icenowy Zheng <uwu@...nowy.me>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Drew Fustini <fustini@...nel.org>,
 Guo Ren <guoren@...nel.org>, Fu Wei <wefu@...hat.com>,
 Philipp Zabel <p.zabel@...gutronix.de>, Heiko Stuebner <heiko@...ech.de>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Michal Wilczynski <m.wilczynski@...sung.com>
Cc: Han Gao <rabenda.cn@...il.com>, Yao Zi <ziyao@...root.org>,
 dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v3 2/9] dt-bindings: display: add verisilicon,dc

On 27/11/2025 14:47, Icenowy Zheng wrote:
> 在 2025-11-26星期三的 11:22 +0100，Krzysztof Kozlowski写道：
>> On 26/11/2025 10:50, Icenowy Zheng wrote:
>>>>> +maintainers:
>>>>> +  - Icenowy Zheng <uwu@...nowy.me>
>>>>> +
>>>>> +properties:
>>>>> +  $nodename:
>>>>> +    pattern: "^display@[0-9a-f]+$"
>>>>> +
>>>>> +  compatible:
>>>>> +    items:
>>>>> +      - enum:
>>>>> +          - thead,th1520-dc8200
>>>>> +      - const: verisilicon,dc
>>>>
>>>> I do not see any explanation of exception for generic
>>>> compatibles,
>>>> maybe
>>>> except "self-identification" remark. Rob already pointed this
>>>> out, so
>>>> be
>>>> explicit in commit msg why you are using a generic compatible.
>>>
>>> Well I only get the meaning of "a SoC specific compatible is
>>> required"
>>> in his review message.
>>>
>>> I think my binding now requires both a SoC-specific compatible and
>>> a
>>> generic compatible, which should be okay to satisfy Rob's original
>>> review.
>>
>> You will get then the same questions for me - what justifies generic
>> compatible. You should be on this explicit, because otherwise people
>> misinterpret some commits and patches, and they think the generic
>> compatible is allowed for them as well.
> 
> I came across a comment on Mali Valhall bindings that says `Mali
> Valhall GPU model/revision is fully discoverable`, just after the
> compatible string.
> 
> Should I add a comment like this, or should I make things more clear in
> the commit message?

Just say in the commit msg in the sentence about "self-identification
facility" that therefore you use generic compatible (or "generic
compatible is suitable").

Please trim the context when replying. Look below:

> 
>>
>>>
>>>>
>>>>> +
>>>>> +  reg:
>>>>> +    maxItems: 1
>>>>> +
>>>>> +  interrupts:
>>>>> +    maxItems: 1
>>>>> +
>>>>> +  clocks:
>>>>> +    minItems: 4
>>>>
>>>> This is not flexible. Device either has or has not these clocks.
>>>
>>> The existence of all these clocks are verified by diagrams in
>>> manuals
>>
>> So not flexible, then:
>>
>>> of two different SoCs with DC8200 (T-Head TH1520 and StarFive
>>> JH7110).
>>>
>>> Maybe a explicit `maxItems: 5` is needed here, but as my DT passes
>>> dtbs_check, I don't think it's necessary?
>>
>> No, drop minItems only.
>>
>>>
>>> Or maybe I should drop the flexibility now and use a `minItems: 5`
>>> here
>>> (and leave DC8000 support as another story)? (The Eswin EIC7700
>>> manual
>>> does not have a diagram showing external connections of the DC,
>>> like
>>> the two SoCs I mentioned above).
>>
>> You document here only the devices explicitly mentioned in the
>> binding.
>> You cannot add here constraints or clocks for some device which is
>> not
>> in the binding and I see only th1520 in the binding.
>>
>> Best regards,
>> Krzysztof
> 

Is all this needed for me? If it is there I will waste time scrolling
through it looking for your questions.

Think how your patchset and replies are received by reviewer.


Best regards,
Krzysztof