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

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

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)

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?

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.

-Sergey

> 
> Rob