linux-kernel - Re: [PATCH net-next v1 2/7] dt-bindings: net: phy: add PoDL PSE property

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Date:   Mon, 22 Aug 2022 21:34:47 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Rob Herring <robh@...nel.org>
Cc:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
        David Jander <david@...tonic.nl>
Subject: Re: [PATCH net-next v1 2/7] dt-bindings: net: phy: add PoDL PSE
 property

On Mon, Aug 22, 2022 at 01:45:34PM -0500, Rob Herring wrote:
> On Fri, Aug 19, 2022 at 02:01:04PM +0200, Oleksij Rempel wrote:
> > Add property to reference node representing a PoDL Power Sourcing Equipment.
> > 
> > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > ---
> >  Documentation/devicetree/bindings/net/ethernet-phy.yaml | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/ethernet-phy.yaml b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> > index ed1415a4381f2..49c74e177c788 100644
> > --- a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> > +++ b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> > @@ -144,6 +144,12 @@ properties:
> >        Mark the corresponding energy efficient ethernet mode as
> >        broken and request the ethernet to stop advertising it.
> >  
> > +  ieee802.3-podl-pse:
> > +    $ref: /schemas/types.yaml#/definitions/phandle
> > +    description:
> > +      Specifies a reference to a node representing a Power over Data Lines
> > +      Power Sourcing Equipment.
> 
> Ah, here is the consumer.
> 
> Why do you anything more than just a -supply property here for the 
> PoE/PoDL supply? The only reason I see is you happen to want a separate 
> driver for this and a separate node happens to be a convenient way to 
> instantiate drivers in Linux. Convince me otherwise.

The regulator binding provides a lot of very useful properties, which
look to do a good job describing the regulator part of a PoE/PeDL
supplier side. What however is missing is the communication part, the
power provider and the power consumer communicate with each other, via
a serial protocol. They negotiate the supply of power, a sleep mode
where power is reduced, but not removed, etc.

So a Power Sourcing Equipment driver is very likely to have a
regulator embedded in it, but its more than a regulator.

	 Andrew