Re: [PATCH v2 03/15] dt-bindings: memory: snps: Convert the schema to being generic

[Serge Semin <fancer.lancer@gmail.com>]

On Tue, Sep 27, 2022 at 05:02:40PM -0500, Rob Herring wrote:
> 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.

Sigh... I see. Will fix it in the next patchset round.

-Sergey

> 
> Rob