linux-kernel - Re: [PATCH] dt-bindings: mmc: fsl-imx-esdhc: allow more compatible combinations

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Date:   Sat, 7 Jan 2023 16:01:05 +0100
From:   Andreas Kemnade <andreas@...nade.info>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     ulf.hansson@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, shawnguo@...nel.org,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-imx@....com, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: mmc: fsl-imx-esdhc: allow more compatible
 combinations

On Sat, 7 Jan 2023 15:09:24 +0100
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 07/01/2023 15:07, Andreas Kemnade wrote:
> > On Sat, 7 Jan 2023 15:00:56 +0100
> > Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> > 
> > [...]  
> >>>> I asked to remove half-compatible. Not to enforce.
> >>>>    
> > so you are saying that allowing
> > compatible = "A", "B" 
> > is not ok, if B is not fully compatible. I agree with that
> > one.  
> 
> I did not say that. It's not related to this problem.
> 
You said "I asked to remove half-compatible" that means to me
remove "B" if not fully compatible with A which sounds sane to me.

> Again - you cannot have device which is and is not compatible with
> something else. It's not a Schroedinger's cat to be in two states,
> unless you explicitly document the cases (there are exception). If this
> is such exception, it requires it's own documentation.
> 
so conclusion:
If having A and B half-compatible with A:

compatible = "A" only: is allowed to specifiy it the binding (status quo),
  but not allowed to make the actual dtsi match the binding documentation
  https://lore.kernel.org/linux-devicetree/72e1194e10ccb4f87aed96265114f0963e805092.camel@pengutronix.de/
  and
  https://lore.kernel.org/linux-devicetree/20210924091439.2561931-5-andreas@kemnade.info/

compatible = "A", "B" in the binding definition: is not allowed ("I asked to remove
   half-compatible" (= removing B))

having mismatch between binding definition and devicetree causes dtbs_check errors
   -> also not nice.

I rather drop this patch and learn to live with dtbs_check errors
for this one since I have no idea how to proceed. All roads are blocked.
This all causes too much churn.

Regards,
Andreas