linux-kernel - Re: [PATCH v14 1/2] drm: add kms driver for loongson display controller

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Message-ID: <69edaf49-359a-229c-c8b4-8aa3af622008@189.cn>
Date:   Mon, 22 May 2023 21:13:21 +0800
From:   Sui Jingfeng <15330273260@....cn>
To:     WANG Xuerui <kernel@...0n.name>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Li Yi <liyi@...ngson.cn>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian Koenig <christian.koenig@....com>,
        Emil Velikov <emil.l.velikov@...il.com>
Cc:     linaro-mm-sig@...ts.linaro.org, loongson-kernel@...ts.loongnix.cn,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Liu Peibao <liupeibao@...ngson.cn>, linux-media@...r.kernel.org
Subject: Re: [PATCH v14 1/2] drm: add kms driver for loongson display
 controller

Hi,

On 2023/5/22 18:25, WANG Xuerui wrote:
> On 2023/5/22 18:17, Sui Jingfeng wrote:
>> Hi,
>>
>> On 2023/5/22 18:05, WANG Xuerui wrote:
>>> On 2023/5/22 17:49, Sui Jingfeng wrote:
>>>> Hi,
>>>>
>>>> On 2023/5/22 17:28, WANG Xuerui wrote:
>>>>> On 2023/5/22 17:25, Sui Jingfeng wrote:
>>>>>> Hi,
>>>>>>
>>>>>> On 2023/5/21 20:21, WANG Xuerui wrote:
>>>>>>>> + * LS3A4000/LS3A5000/LS3A6000 CPU, they are equipped with 
>>>>>>>> on-board video RAM
>>>>>>>> + * typically. While LS2K0500/LS2K1000/LS2K2000 are low cost 
>>>>>>>> SoCs which share
>>>>>>>> + * the system RAM as video RAM, they don't has a dediacated VRAM.
>>>>>>>
>>>>>>> CPU models are not typically prefixed with "LS", so "Loongson 
>>>>>>> 3A4000/3A5000/3A6000".
>>>>>>>
>>>>>> Here is because when you do programming, variable name should 
>>>>>> prefix with letters.
>>>>>
>>>>> Commit messages, comments, and log messages etc. are natural 
>>>>> language, so it's better to treat them differently. No problem to 
>>>>> keep code as-is IMO.
>>>>>
>>>> Then you get two name for a single chip,  take  LS7A1000 as an 
>>>> example.
>>>>
>>>> You name it as Loongson 7A1000 in commit message,  and then you 
>>>> have to define another name in the code,  say LS7A1000.
>>>>
>>>> "Loongson 7A1000" is too long,  not as compact as LS7A1000.
>>>>
>>>> This also avoid bind the company name to a specific product, 
>>>> because a company can produce many product.
>>>
>>> Nah, the existing convention is "LS7Xxxxx" for bridges and "Loongson 
>>> 3Axxxx" for CPUs (SoCs like 2K fall under this category too). It's 
>>> better to stick with existing practice so it would be familiar to 
>>> long-time Loongson/LoongArch developers, but I personally don't 
>>> think it will hamper understanding if you feel like doing otherwise.
>>>
>> Can you explain why it is better?
>>
>> is it that the already existing is better ?
>
> It's not about subjective perception of "better" or "worse", but about 
> tree-wide consistency, and about reducing any potential confusion from 
> newcomers. I remember Huacai once pointing out that outsiders usually 
> have a hard time remembering "1, 2, and 3 are CPUs, some 2 are SoCs, 7 
> are bridge chips", and consistently referring to the bridge chips 
> throughout the tree as "LS7A" helped.
>
> In any case, for the sake of consistency, you can definitely refer to 
> the CPU models in natural language like "LS3Axxxx"; just make sure to 
> refactor for example every occurrence in arch/loongarch and other 
> parts of drivers/. That's a lot of churn, though, so I don't expect 
> such changes to get accepted, and that's why the tree-wide consistency 
> should be favored over the local one.
>
There are document[1] which named LS7A1000 bridge chip as Loongson 
7A1000 Bridge,

which is opposed to what you have said "the existing convention is 
LS7Xxxxx for bridges".


there are also plenty projects[2] which encode ls2k1000 as project name, 
which simply

don't fall into the category as you have mentioned("Loongson 3Axxxx").


See [1][2] for reference, how to explain this phenomenon then?


[1] 
https://loongson.github.io/LoongArch-Documentation/Loongson-7A1000-usermanual-EN

[2] https://github.com/zhaozhi0810/pmon-ls2k1000-2022