linux-kernel - Re: [PATCH 2/3] dt-bindings: usb: atmel: Add Microchip LAN966x compatible string

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Date:   Fri, 20 May 2022 15:38:36 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Herve Codina <herve.codina@...tlin.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 2/3] dt-bindings: usb: atmel: Add Microchip LAN966x
 compatible string

On 20/05/2022 15:02, Herve Codina wrote:
> On Fri, 20 May 2022 14:50:24 +0200
> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> 
>> On 20/05/2022 14:21, Herve Codina wrote:
>>>>> I think it makes sense to keep 'microchip,lan966x-udc' for the USB
>>>>> device controller (same controller on LAN9662 and LAN9668) and so
>>>>> keeping the same rules as for other common parts.    
>>>>
>>>> Having wildcard was rather a mistake and we already started correcting
>>>> it, so keeping the "mistake" neither gives you consistency, nor
>>>> correctness...
>>>>  
>>>
>>> I think that the "family" compatible should be present.
>>> This one allows to define the common parts in the common
>>> .dtsi file (lan966x.dtsi in our case).
>>>
>>> What do you think about:
>>> - microchip,lan9662-udc
>>> - microchip,lan9668-udc
>>> - microchip,lan966-udc  <-- Family
>>>
>>> lan966 is defined as the family compatible string since (1) in
>>> bindings/arm/atmel-at91.yaml and in Documentation/arm/microchip.rst
>>>   
>>
>> You can add some family compatible, if it makes sense. I don't get why
>> do you mention it - we did not discuss family names, but using
>> wildcards... Just please do not add wildcards.
> 
> Well, I mentioned it as I will only use the family compatible string
> and not the SOC (lan9662 or lan9668) compatible string in lan966x.dtsi.
> In this case, the family compatible string can be seen as a kind of
> "wildcard".

I understood as "the "family" compatible should be present" as you want
to add it as a fallback. It would be okay (assuming devices indeed share
family design). If you want to use it as the only one, then it is again
not a recommended approach. Please use specific compatibles.

I mean, why do we have this discussion? What is the benefit for you to
implement something not-recommended by Devicetree spec and style?

Best regards,
Krzysztof