netdev - Re: [PATCH RFC 0/3] dt-bindings: net: Add network-class.yaml schema

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Message-ID: <20230206163154.GA9004@jannau.net>
Date:   Mon, 6 Feb 2023 17:31:54 +0100
From:   Janne Grunau <j@...nau.net>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Mailing List <devicetree-spec@...r.kernel.org>,
        Kalle Valo <kvalo@...nel.org>, van Spriel <arend@...adcom.com>,
        Jérôme Pouiller <jerome.pouiller@...abs.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org
Subject: Re: [PATCH RFC 0/3] dt-bindings: net: Add network-class.yaml schema

On 2023-02-03 08:41:28 -0600, Rob Herring wrote:
> On Fri, Feb 3, 2023 at 7:56 AM Janne Grunau <j@...nau.net> wrote:
> >
> > The Devicetree Specification, Release v0.3 specifies in section 4.3.1
> > a "Network Class Binding". This covers MAC address and maximal frame
> > size properties. "local-mac-address" and "mac-address" with a fixed
> > address-size of 48 bits is already in the ethernet-controller.yaml
> > schema so move those over.
> > I think the only commonly used values for address-size are 48 and 64
> > bits (EUI-48 and EUI-64). Unfortunately I was not able to restrict the
> > mac-address size based on the address-size. This seems to be an side
> > effect of the array definition and I was not able to restrict "minItems"
> > or "maxItems" based on the address-size value in an "if"-"then"-"else"
> > block.
> > An easy way out would be to restrict address-size to 48-bits for now.
> 
> I've never seen 64-bits used...

ZigBee and 6LoWPAN use 64-bits for example. Let's hardcode 48 bits for 
now as that's what all in-tree devicetrees implicitly use. If needed it 
can be changed later.

> > I've ignored "max-frame-size" since the description in
> > ethernet-controller.yaml claims there is a contradiction in the
> > Devicetree specification. I suppose it is describing the property
> > "max-frame-size" with "Specifies maximum packet length ...".
> 
> Please include it and we'll fix the spec. It is clearly wrong. 2 nios
> boards use 1518 and the consumer for them says it is MTU. Everything
> else clearly uses mtu with 1500 or 9000.

Ok, the example in the pdf is 'max-frame-size = <1518>;'. I'll include 
it with the description of ethernet-controller.yaml which specifies it 
as MTU.

Janne