Re: [RFC PATCH] dt-bindings: add a jsonschema binding example

[Grant Likely]

On 23/04/2018 17:49, Geert Uytterhoeven wrote:
> Hi Grant,
>
> On Mon, Apr 23, 2018 at 4:47 PM, Grant Likely <grant.likely@xxxxxxx> wrote:
> > On 21/04/2018 02:28, Rob Herring wrote:
> > > On Fri, Apr 20, 2018 at 4:00 PM, Frank Rowand <frowand.list@xxxxxxxxx>
> > > wrote:
> > > > > +  interrupts:
> > > > > +    # Either 1 or 2 interrupts can be present
> > > > > +    minItems: 1
> > > > > +    maxItems: 2
> > > > > +    items:
> > > > > +      - description: tx or combined interrupt
> > > > > +      - description: rx interrupt
> > > > > +
> > > > > +    description: |
> > > > > +      A variable number of interrupts warrants a description of what
> > > > > conditions
> > > > > +      affect the number of interrupts. Otherwise, descriptions on
> > > > > standard
> > > > > +      properties are not necessary.
> > > > > +
> > > > > +  interrupt-names:
> > > > > +    # minItems must be specified here because the default would be 2
> > > > > +    minItems: 1
> > > >
> > > > Why the difference between the interrupts property and the
> > > > interrupt-names
> > > > property (specifying maxItems for interrupt, but not interrupt-names)?
> > >
> > > I should probably have maxItems here too.
> > >
> > > > Others have already commented on a desire to have a way to specify that
> > > > number of interrupts should match number of interrupt-names.
> > >
> > > Yeah, but I don't see a way to do that. You could stick the array size
> > > constraints in a common definition and have a $ref to that definition
> > > from both, but that doesn't really save you too much.
> >
> >
> > There has been discussions in the jsonschema community regarding
> > referencing data in the document when applying the schema.
> >
> > https://github.com/json-schema-org/json-schema-spec/issues/549
> >
> > However, those discussions are ongoing and have been pushed back to
> > after draft-8 (the current release is draft-7). We can instead define
> > DT-specific keywords and extend the validator to make it do what we
> > want. We need to do something very similar to validate that the length
> > of tuples in 'reg', 'interrupts', and '*gpios' match the '#*-cells' values.
>
> Checking that property lengths match the corresponding #*-cells cannot
> be done for a schema, but only for the final DTS, as #*-cells is a property
> of the target node, right?

It can be done in the schema checking of the target node. For example,
given a GPIO specifier of:

gpios = <&gpio1 0> <&gpio2 4 1> <&gpio2 3 0>;

The validation engine could validate that the &gpio1 and &gpio2 targets
have the same length as the associated gpio descriptor tuples. (ex.
gpio1 needs #gpio-cells=<1>; and gpio2 needs #gpio-cells=<2>; If the
tuples are the wrong size, then validation should fail.

g.
> Gr{oetje,eeting}s,
>
>                          Geert

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