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

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Message-ID: <20230108182049.679de9f9@aktux>
Date:   Sun, 8 Jan 2023 18:20:49 +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 Sun, 8 Jan 2023 15:45:44 +0100
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 07/01/2023 16:54, Andreas Kemnade wrote:
> > 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".  
> 
> Sorry, I don't follow. I also do not understand what "matching" means in
> these terms (binding driver? of_match?) and also I do not know what is
> the "above definition".
> 
> Devicetree spec defines the compatibility - so this is the definition.
> There will be differences when applying it to different cases.
> 
Ok, lets stop talking about A and B, lets be more specific.
Hmm, I try to insert the missing bits here:

I am not convinced anymore that my patch is correct
- for dtb compatible formality
- for pure technical reasons

I am not convinced that your proposal is correct either.
- for pure technical reasons (for same resan as you state)

Especially this part I consider faulty:
+      - items:
+          - const: fsl,imx6sx-usdhc
+          - const: fsl,imx6sl-usdhc

Keyword: ESDHC_FLAG_STATE_LOST_IN_LPMODE (detailed that in
an earlier mail).

Regards
Andreas