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

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Message-ID: <20230107165457.30f4dddf@aktux>
Date:   Sat, 7 Jan 2023 16:54:57 +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 16:07:35 +0100
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 07/01/2023 16:01, Andreas Kemnade wrote:
> > 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))  
> 
> No, half compatible is the A in such case.
> 
I think that there is some misunderstanding in here. I try once again.

Define compatible with "X" here:
To me it means:

device fully works with flags defined in:

static const struct esdhc_soc_data usdhc_X_data = { ... };

with usdhc_X_data referenced in
        { .compatible = "X", .data = &usdhc_X_data, },


So if there is only "A" matching with above definition of compatibility
  compatible = "A" would sound sane to me.

And scrutinizing the flags more and not just wanting to achieve error-free
dtbs_check, I think is this in most cases where there is only "A". 

If there is "A" and "B" which match that compatibility definition, you
say that only compatible = "A", "B" is allowed, but not compatible = "A".
In that case I would have no problem with that.

But if there is only "A" but no "B" matching the above definition, I would expect
that only compatible = "A" is allowed but *not* compatible = "A", "B".

Regards,
Andreas