linux-kernel - Re: [PATCH net-next v6 11/17] dt-bindings: net: pse-pd: Add another way of describing several PSE PIs

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Date: Wed, 3 Apr 2024 09:44:48 -0500
From: Rob Herring <robh@...nel.org>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Kory Maincent <kory.maincent@...tlin.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Russ Weight <russ.weight@...ux.dev>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, Mark Brown <broonie@...nel.org>,
	Frank Rowand <frowand.list@...il.com>, Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, devicetree@...r.kernel.org,
	Dent Project <dentproject@...uxfoundation.org>
Subject: Re: [PATCH net-next v6 11/17] dt-bindings: net: pse-pd: Add another
 way of describing several PSE PIs

On Tue, Apr 02, 2024 at 05:47:58PM +0200, Oleksij Rempel wrote:
> On Tue, Apr 02, 2024 at 08:26:37AM -0500, Rob Herring wrote:
> > > +          pairsets:
> > > +            $ref: /schemas/types.yaml#/definitions/phandle-array
> > > +            description:
> > > +              List of phandles, each pointing to the power supply for the
> > > +              corresponding pairset named in 'pairset-names'. This property
> > > +              aligns with IEEE 802.3-2022, Section 33.2.3 and 145.2.4.
> > > +              PSE Pinout Alternatives (as per IEEE 802.3-2022 Table 145\u20133)
> > > +              |-----------|---------------|---------------|---------------|---------------|
> > > +              | Conductor | Alternative A | Alternative A | Alternative B | Alternative B |
> > > +              |           |    (MDI-X)    |     (MDI)     |      (X)      |      (S)      |
> > > +              |-----------|---------------|---------------|---------------|---------------|
> > > +              | 1         | Negative VPSE | Positive VPSE | \u2014             | \u2014             |
> > > +              | 2         | Negative VPSE | Positive VPSE | \u2014             | \u2014             |
> > > +              | 3         | Positive VPSE | Negative VPSE | \u2014             | \u2014             |
> > > +              | 4         | \u2014             | \u2014             | Negative VPSE | Positive VPSE |
> > > +              | 5         | \u2014             | \u2014             | Negative VPSE | Positive VPSE |
> > > +              | 6         | Positive VPSE | Negative VPSE | \u2014             | \u2014             |
> > > +              | 7         | \u2014             | \u2014             | Positive VPSE | Negative VPSE |
> > > +              | 8         | \u2014             | \u2014             | Positive VPSE | Negative VPSE |
> > > +            minItems: 1
> > > +            maxItems: 2
> > 
> > "pairsets" does not follow the normal design pattern of foos, foo-names, 
> > and #foo-cells. You could add #foo-cells I suppose, but what would cells 
> > convey? I don't think it's a good fit for what you need.
> > 
> > The other oddity is the number of entries and the names are fixed. That 
> > is usually defined per consumer. 
> > 
> > As each entry is just a power rail, why can't the regulator binding be 
> > used here?
> 
> I'm not against describing it consequent with regulator till the wire
> end, but right now I have no idea how it should be described by using
> regulator bindings. There are maximum 2 rails going in to PSE PI on one
> side and 4 rails with at least 5 combinations supported by standard on
> other side. Instead of inventing anything new, I suggested to describe
> supported output combinations by using IEEE 802.3 standard.

There's 4 combinations above, what's the 5th combination? SPE?

Seems to me you just describe the 2 rails going to the connector and 
then describe all the variations the connector supports. The PSE 
(h/w) has little to do with which variations are supported, right? 
For example, MDI-X vs. MDI support is determined by the PHY, right? Or 
it has to be supported by both the PHY and PSE?

Rob