linux-hardening - Re: [PATCH v2 02/14] dt-bindings: dpll: Add support for Microchip Azurite chip family

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Message-ID: <20250414-residual-unblended-c21c7bc6eeb2@spud>
Date: Mon, 14 Apr 2025 18:19:41 +0100
From: Conor Dooley <conor@...nel.org>
To: Ivan Vecera <ivecera@...hat.com>
Cc: Andrew Lunn <andrew@...n.ch>, Prathosh.Satish@...rochip.com,
	krzk@...nel.org, netdev@...r.kernel.org, vadim.fedorenko@...ux.dev,
	arkadiusz.kubalewski@...el.com, jiri@...nulli.us, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, lee@...nel.org,
	kees@...nel.org, andy@...nel.org, akpm@...ux-foundation.org,
	mschmidt@...hat.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 02/14] dt-bindings: dpll: Add support for Microchip
 Azurite chip family

On Fri, Apr 11, 2025 at 11:56:15AM +0200, Ivan Vecera wrote:
> 
> 
> On 10. 04. 25 11:12 odp., Andrew Lunn wrote:
> > On Thu, Apr 10, 2025 at 08:33:31PM +0200, Ivan Vecera wrote:
> > > 
> > > 
> > > On 10. 04. 25 7:36 odp., Andrew Lunn wrote:
> > > > > Prathosh, could you please bring more light on this?
> > > > > 
> > > > > > Just to clarify, the original driver was written specifically with 2-channel
> > > > > > chips in mind (ZL30732) with 10 input and 20 outputs, which led to some confusion of using zl3073x as compatible.
> > > > > > However, the final version of the driver will support the entire ZL3073x family
> > > > > > ZL30731 to ZL30735 and some subset of ZL30732 like ZL80732 etc
> > > > > > ensuring compatibility across all variants.
> > > > 
> > > > Hi Prathosh
> > > > 
> > > > Your email quoting is very odd, i nearly missed this reply.
> > > > 
> > > > Does the device itself have an ID register? If you know you have
> > > > something in the range ZL30731 to ZL30735, you can ask the hardware
> > > > what it is, and the driver then does not need any additional
> > > > information from DT, it can hard code it all based on the ID in the
> > > > register?
> > > > 
> > > > 	Andrew
> > > > 
> > > Hi Andrew,
> > > yes there is ID register that identifies the ID. But what compatible should
> > > be used?
> > > 
> > > microchip,zl3073x was rejected as wildcard and we should use all
> > > compatibles.
> > 
> > You have two choices really:
> > 
> > 1) You list each device with its own compatible, because they are in
> > fact not compatible. You need to handle each one different, they have
> > different DT properties, etc. If you do that, please validate the ID
> > register against the compatible and return -ENODEV if they don't
> > match.
> > 
> > 2) You say the devices are compatible. So the DT compatible just
> > indicates the family, enough information for the driver to go find the
> > ID register. This does however require the binding is the same for all
> > devices. You cannot have one family member listing 10 inputs in its
> > binding, and another family member listing 20.
> > 
> > If you say your devices are incompatible, and list lots of
> > compatibles, you can then use constraints in the yaml, based on the
> > compatible, to limit each family member to what it supports.
> > 
> > My guess is, you are going to take the first route.
> 
> Yes, this looks reasonable... in this case should I use
> microchip,zl3073x.yaml like e.g. gpio/gpio-pca95xx.yaml?

No, please pick one of the compatibles in the file and name the same as
one of those.

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