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From:   Rob Herring <robh@kernel.org>
Date:   Tue, 27 Sep 2022 17:02:40 -0500
Message-ID: <CAL_JsqJgkY=xb8ED_oiUBPbjV7dKRd3MRJq+jNVXuJhE3L3t_Q@mail.gmail.com>
Subject: Re: [PATCH v2 03/15] dt-bindings: memory: snps: Convert the schema to
 being generic
To:     Serge Semin <fancer.lancer@gmail.com>
Cc:     Serge Semin <Sergey.Semin@baikalelectronics.ru>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Michal Simek <michal.simek@xilinx.com>,
        Borislav Petkov <bp@alien8.de>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Tony Luck <tony.luck@intel.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Manish Narani <manish.narani@xilinx.com>,
        Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
        Michail Ivanov <Michail.Ivanov@baikalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>,
        Punnaiah Choudary Kalluri 
        <punnaiah.choudary.kalluri@xilinx.com>,
        Dinh Nguyen <dinguyen@kernel.org>,
        James Morse <james.morse@arm.com>,
        Robert Richter <rric@kernel.org>, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-edac@vger.kernel.org,
        linux-kernel@vger.kernel.org, Krzysztof Kozlowski <krzk@kernel.org>
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On Mon, Sep 26, 2022 at 5:56 AM Serge Semin <fancer.lancer@gmail.com> wrote:
>
> On Mon, Sep 12, 2022 at 09:32:19AM -0500, Rob Herring wrote:
> > On Sat, Sep 10, 2022 at 10:56:47PM +0300, Serge Semin wrote:
> > > At the current state the DW uMCTL2 DDRC DT-schema can't be used as the
> > > common one for all the IP-core-based devices due to the compatible string
> > > property constraining the list of the supported device names. In order to
> > > fix that we suggest to update the compatible property constraints so one
> > > would permit having any value aside with the generic device names. At the
> > > same time the generic DT-schema selection must be restricted to the
> > > denoted generic devices only so not to permit the generic fallback
> > > compatibles. Finally since the generic schema will be referenced from the
> > > vendor-specific DT-bindings with possibly non-standard properties defined
> > > it must permit having additional properties specified.
> > >
> > > Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> > >
> > > ---
> > >
> > > Note alternatively we could drop the "additionalProperties" keyword
> > > modification since currently there is no actual device available with the
> > > properties not listed in the generic DT-schema.
> >
>
> > Normally, this has required 2 schema files. However, I think you can
> > do something like this:
> >
> > if:
> >   compatible:
> >     enum:
> >       - snps,ddrc-3.80a
> >       - snps,dw-umctl2-ddrc
> >       - xlnx,zynqmp-ddrc-2.40a
> > then:
> >   unevaluatedProperties: false
> >
> >
> > But please make sure that actually catches undocumented properties
> > because unevaluateProperties under 'then' is not something I've tried.
>
> Oh, I wish this would work! Alas it doesn't. AFAIU the schemas under
> the "then" and "else" keywords are considered as separate schemas
> and are independently applied to the DT node. As soon as I added the
> construction suggested by you the schema evaluation started failing
> with error as none of the DT-node properties in the examples are valid:
>
> < ... /snps,dw-umctl2-ddrc.example.dtb: memory-controller@fd070000:
> <     Unevaluated properties are not allowed ('compatible', 'reg', interrupts', 'interrupt-names', '$nodename' were unexpected)
>
> < ... /snps,dw-umctl2-ddrc.example.dtb: memory-controller@3d400000:
> <     Unevaluated properties are not allowed ('compatible', 'reg', 'interrupts', 'interrupt-names', 'clocks', 'clock-names', '$nodename' were unexpected)

Indeed. While unevaluatedProperties takes if/then/else into account,
flipping it around doesn't.

> Any suggestion of how this could be fixed? Perhaps updating the
> dtschema tool anyhow? (I failed to find a quick-fix for it) Creating
> an additional separate schema with the common properties seems a bit
> overkill in this case. On the other hand is there a decent
> alternative?

I don't think there is any other fix.

> What about accepting what I suggested in this patch? It does permit
> additional properties, but we won't need to have a separate schema
> with just several common properties.

No. You can't have it both ways. Either it is a common schema or a
specific device schema.

Rob