linux-kernel - Re: [RFC PATCH 1/3] dt-bindings: arm64: bcmbca: Merge BCM4908 into BCMBCA

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Message-ID: <e4356c5e89492eb690e3dc863ba281bd@milecki.pl>
Date:   Wed, 13 Jul 2022 12:50:55 +0200
From:   Rafał Miłecki <rafal@...ecki.pl>
To:     William Zhang <william.zhang@...adcom.com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Linux ARM List <linux-arm-kernel@...ts.infradead.org>,
        kursad.oney@...adcom.com, anand.gore@...adcom.com,
        dan.beygelman@...adcom.com, f.fainelli@...il.com,
        Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
        joel.peshkin@...adcom.com,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/3] dt-bindings: arm64: bcmbca: Merge BCM4908 into
 BCMBCA

On 2022-07-13 02:57, William Zhang wrote:
> On 7/12/22 11:18, Krzysztof Kozlowski wrote:
>> On 12/07/2022 19:37, William Zhang wrote:
>>>>> +      - description: BCM4908 Family based boards
>>>>> +        items:
>>>>> +          - enum:
>>>>> +              # BCM4908 SoC based boards
>>>>> +              - brcm,bcm94908
>>>>> +              - asus,gt-ac5300
>>>>> +              - netgear,raxe500
>>>>> +              # BCM4906 SoC based boards
>>>>> +              - brcm,bcm94906
>>>>> +              - netgear,r8000p
>>>>> +              - tplink,archer-c2300-v1
>>>>> +          - enum:
>>>>> +              - brcm,bcm4908
>>>>> +              - brcm,bcm4906
>>>>> +              - brcm,bcm49408
>>>> 
>>>> This is wrong.  brcm,bcm94908 followed by brcm,bcm4906 does not look
>>>> like valid list of compatibles.
>>>> 
>>> For 4908 board variant, it will need to be followed by 4908 chip. 
>>> Sorry
>>> for the basic question but is there any requirement to enforce this 
>>> kind
>>> of rule?  I would assume dts writer know what he/she is doing and 
>>> select
>>> the right combination.
>> 
>> The entire point of DT schema is to validate DTS. Combination like 
>> above
>> prevents that goal.
>> 
>> Best regards,
>> Krzysztof
> Understand the DT schema purpose. But items property allows multiple
> enums in the list which gives a lot of flexibility but make it hard to
> validate. I am not familiar with DT schema, is there any directive to
> specify one enum value depending on another so dts validation tool can
> report error if combination is wrong?
> 
> This is our preferred format of all bcmbca compatible string
> especially when we could have more than 10 chip variants for the same
> chip family and we really want to work on the chip family id.  We will
> make sure they are in the right combination in our own patch and patch
> from other contributors. Would this work? If not, I will probably have
> to revert the change of 4908(maybe append brcm,bcmbca as this chip
> belongs to the same bca group) and use "enum board variant", "const
> main chip id", "brcm,bca" for all other chips as our secondary choice.

I'm not sure why I didn't even receive 1/3 and half of discussion
e-mails.

You can't just put all strings into a single bag and allow mixing them
in any combos. Please check how it's properly handled in the current
existing binding:
Documentation/devicetree/bindings/arm/bcm/brcm,bcm4908.yaml

Above binding enforces that non-matching compatible strings are not used
together.