linux-kernel - Re: [EXTERNAL]Re: [PATCH net-next 1/2] dt-bindings: net: pse-pd: Add bindings for Si3474 PSE controller

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Message-ID: <b3db09da-72f0-465f-b177-ff14fd53608b@kernel.org>
Date: Fri, 16 May 2025 15:37:50 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Piotr Kubik <piotr.kubik@...ran.com>,
 Oleksij Rempel <o.rempel@...gutronix.de>,
 Kory Maincent <kory.maincent@...tlin.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [EXTERNAL]Re: [PATCH net-next 1/2] dt-bindings: net: pse-pd: Add
 bindings for Si3474 PSE controller

On 15/05/2025 17:20, Piotr Kubik wrote:
> On 5/13/25 10:24, Krzysztof Kozlowski wrote:
>> On 13/05/2025 00:05, Piotr Kubik wrote:
>>> +
>>> +maintainers:
>>> +  - Piotr Kubik <piotr.kubik@...ran.com>
>>> +
>>> +allOf:
>>> +  - $ref: pse-controller.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - skyworks,si3474
>>> +
>>> +  reg-names:
>>> +    items:
>>> +      - const: main
>>> +      - const: slave
>>
>> s/slave/secondary/ (or whatever is there in recommended names in coding
>> style)
>>
> 
> Well I was thinking about it and decided to use 'slave' for at least two reasons:
> - si3474 datasheet calls the second part of IC (we configure it here) this way

This could be a reason, but specs are changing over time (see I2C, I3C)
to include different namings. If this annoys certain government sending
their executive directives, then even better.

> - description of i2c_new_ancillary_device() calls this device explicitly slave multiple times

Old driver code should not be an argument. If code changes, which it can
anytime, are you going to change binding? No, because such change in the
binding would not be allowed.

> 
>>> +
>>> +  reg:
>>
>> First reg, then reg-names. Please follow other bindings/examples.
>>
>>> +    maxItems: 2
>>> +
>>> +  channels:
>>> +    description: The Si3474 is a single-chip PoE PSE controller managing
>>> +      8 physical power delivery channels. Internally, it's structured
>>> +      into two logical "Quads".
>>> +      Quad 0 Manages physical channels ('ports' in datasheet) 0, 1, 2, 3
>>> +      Quad 1 Manages physical channels ('ports' in datasheet) 4, 5, 6, 7.
>>> +      This parameter describes the relationship between the logical and
>>> +      the physical power channels.
>>
>> How exactly this maps here logical and physical channels? You just
>> listed channels one after another...
> 
> yes, here in this example it is 1 to 1 simple mapping, but in a real world,
> depending on hw connections, there is a possibility that 
> e.g. "pse_pi0" will use "<&phys0_4>, <&phys0_5>" pairset for lan port 3.
> 

Ack, I see that's actually common for pse-pd. It's fine.

Best regards,
Krzysztof