linux-kernel - Re: [PATCH v2 1/3] dt-bindings: iio: adc: sophgo,cv18xx-saradc.yaml: Add Sophgo SARADC binding documentation

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Message-ID: <20240709092722.1a3a2482@xps-13>
Date: Tue, 9 Jul 2024 09:27:22 +0200
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, Conor Dooley <conor@...nel.org>,
 Thomas Bonnefille <thomas.bonnefille@...tlin.com>, Jonathan Cameron
 <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, Rob Herring
 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Chen Wang <unicorn_wang@...look.com>, Inochi Amaoto
 <inochiama@...look.com>, Paul Walmsley <paul.walmsley@...ive.com>, "Palmer
 Dabbelt" <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, "Thomas
 Petazzoni" <thomas.petazzoni@...tlin.com>, <linux-iio@...r.kernel.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: iio: adc:
 sophgo,cv18xx-saradc.yaml: Add Sophgo SARADC binding documentation

Hi Jonathan,

> > > > * DO use fallback compatibles when devices are the same as or a subset
> > > >   of prior implementations.
> > > > 
> > > > I believe we fall in the "devices are the same" category, so I would
> > > > have myself wrote a similar binding here with a compatible matching
> > > > them all, plus a hardware-implementation-specific compatible as well;
> > > > just in case.    
> > > 
> > > Fallback from one model to another. There is no "another" model here,
> > > but wildcard. There is no such device as cv18xx, right?  
> > 
> > No there is not. But I don't think there is a "base" model either.
> > Just multiple SoCs named cv18<something> with apparently the same ADC.
> > 
> > So actually I guess the discussion here is about the wildcard
> > compatible. It feels strange to me to have no generic compatible either
> > with a wildcard or with a "base" implementation (because there is
> > probably none). So I guess the solution here is to just list a single
> > specific compatible in the end.
> 
> It comes from long experience of silicon vendors not being consistent
> with part naming.

Oh, agreed :-)

>  Far too often we've had a nice generic wild card
> entry and along comes the vendor with a new part in the middle
> of that range that is completely incompatible.  Then we end up with
> people assuming the wildcard means it will work and a bunch of bug
> reports.  Hence no wild cards, just define first supported part as your
> 'base' and go from there.

I see what you mean. I must admit I'm not a big fan of naming
compatibles (and drivers) after a working base rather than a good
enough wildcard, but I do understand your point and kind of agree with
it actually.

> It's even more fun when a vendor driver papers over the differences
> and so it 'works', but the upstream one doesn't.  In extreme case
> because a different driver entirely is required.
> 
> So basically we don't trust silicon vendors :)
> Speaking as someone who works for one - I think that's entirely
> reasonable!!

Haha <3

Thanks (once again) for your valuable inputs!
Miquèl