linux-kernel - Re: [PATCH v3 1/8] dt-bindings: usb: ti,j721e-usb: drop useless compatible list

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Date: Mon, 26 Feb 2024 11:33:06 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Conor Dooley" <conor@...nel.org>
Cc: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, "Rob Herring"
 <robh+dt@...nel.org>, "Krzysztof Kozlowski"
 <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley" <conor+dt@...nel.org>,
 "Roger Quadros" <rogerq@...nel.org>, "Peter Chen" <peter.chen@...nel.org>,
 "Pawel Laszczak" <pawell@...ence.com>, "Nishanth Menon" <nm@...com>,
 "Vignesh Raghavendra" <vigneshr@...com>, "Tero Kristo" <kristo@...nel.org>,
 "Thomas Petazzoni" <thomas.petazzoni@...tlin.com>,
 Grégory Clement <gregory.clement@...tlin.com>, "Kevin
 Hilman" <khilman@...nel.org>, "Alan Stern" <stern@...land.harvard.edu>,
 <linux-usb@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 1/8] dt-bindings: usb: ti,j721e-usb: drop useless
 compatible list

Hello Conor,

On Fri Feb 23, 2024 at 7:12 PM CET, Conor Dooley wrote:
> On Fri, Feb 23, 2024 at 05:05:25PM +0100, Théo Lebrun wrote:
> > Compatible can be A or B, not A or B or A+B. Remove last option.
> > A=ti,j721e-usb and B=ti,am64-usb.
> > 
> > Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> > ---
> >  Documentation/devicetree/bindings/usb/ti,j721e-usb.yaml | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/usb/ti,j721e-usb.yaml b/Documentation/devicetree/bindings/usb/ti,j721e-usb.yaml
> > index 95ff9791baea..949f45eb45c2 100644
> > --- a/Documentation/devicetree/bindings/usb/ti,j721e-usb.yaml
> > +++ b/Documentation/devicetree/bindings/usb/ti,j721e-usb.yaml
> > @@ -11,12 +11,9 @@ maintainers:
> >  
> >  properties:
> >    compatible:
> > -    oneOf:
> > -      - const: ti,j721e-usb
> > -      - const: ti,am64-usb
> > -      - items:
> > -          - const: ti,j721e-usb
> > -          - const: ti,am64-usb
>
> Correct, this makes no sense. The devices seem to be compatible though,
> so I would expect this to actually be:
> oneOf:
>   - const: ti,j721e-usb
>   - items:
>       - const: ti,am64-usb
>       - const: ti,j721e-usb

I need your help to grasp what that change is supposed to express? Would
you mind turning it into english sentences?

A=ti,j721e-usb and B=ti,am64-usb. My understanding of your proposal is
that a device can either be compat with A or B. But B is compatible
with A so you express it as a list of items. If B is compat with A then
A is compat with B. Does the order of items matter?

I've not applied your proposal to check for dtbs_check but I'd guess it
would throw warnings for the single existing upstream DTSI (as of
v6.8-rc6) that uses "ti,am64-usb"? See:
arch/arm64/boot/dts/ti/k3-am64-main.dtsi.

Thanks Conor!

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com