linux-kernel - Re: [PATCH] dt-bindings: clock: Convert fixed-clock binding to json-schema

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Message-ID: <CAL_JsqJzNBYCMWbZtR37eZd4yx2kc590V+q3603Hg=kG2bZwhw@mail.gmail.com>
Date:   Fri, 11 Jan 2019 12:27:48 -0600
From:   Rob Herring <robh@...nel.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH] dt-bindings: clock: Convert fixed-clock binding to json-schema

On Fri, Jan 11, 2019 at 11:44 AM Stephen Boyd <sboyd@...nel.org> wrote:
>
> Quoting Rob Herring (2019-01-10 14:19:01)
> > Convert the fixed-clock binding to DT schema format using json-schema.
> >
>
> Any pointer to the full schema?

https://github.com/robherring/yaml-bindings/blob/master/schemas/

And the clock schema in particular:
https://github.com/robherring/yaml-bindings/blob/master/schemas/clock.yaml

> > Cc: Michael Turquette <mturquette@...libre.com>
> > Cc: Stephen Boyd <sboyd@...nel.org>
> > Cc: linux-clk@...r.kernel.org
> > Signed-off-by: Rob Herring <robh@...nel.org>
> [...]
> > diff --git a/Documentation/devicetree/bindings/clock/fixed-clock.yaml b/Documentation/devicetree/bindings/clock/fixed-clock.yaml
> > new file mode 100644
> > index 000000000000..8b5628463b90
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/fixed-clock.yaml
> > @@ -0,0 +1,44 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/clock/fixed-clock.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Binding for simple fixed-rate clock sources.
>
> Why does title have a full stop?

Because it was there in the original. My script to extract just takes
the first line of alphanumeric text.

> > +
> > +maintainers:
> > +  - Michael Turquette <mturquette@...libre.com>
> > +  - Stephen Boyd <sboyd@...nel.org>
> > +
> > +properties:
> > +  compatible:
> > +    const: fixed-clock
> > +
> > +  "#clock-cells":
> > +    const: 0
> > +
> > +  clock-frequency: true
>
> Why doesn't this need the $ref: /schemas/types.yaml#/... thing?

You might want to read bindings/example-schema.yaml which tries to
explain some of this.

Standard properties are already defined in the core schemas. So we
only have to say "we use this property" and any binding specific
constraints. In this case, there aren't any other constraints. It is
also needed to be listed here to mark it required and to satisfy
'additionalProperties: false'.

> > +  clock-accuracy:
> > +    description: accuracy of clock in ppb (parts per billion).
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +
> > +  clock-output-names:
> > +    maxItems: 1
>
> Is there a schema for strings?

Yes. The core already covers that '*-names' properties are a list of
strings. So no need to do that again here and we just need to define
how many strings are valid.

> > +
> > +required:
> > +  - compatible
> > +  - "#clock-cells"
> > +  - clock-frequency
> > +
> > +additionalProperties: false
>
> Does this always have to be specified even if it's false?

Yes, the default defined as true by the json-schema spec. In some
cases we don't want to specify it.

> > +
> > +examples:
> > +  - |
> > +    clock {
> > +      compatible = "fixed-clock";
> > +      #clock-cells = <0>;
> > +      clock-frequency = <1000000000>;
> > +      clock-accuracy = <100>;
> > +    };
> > +...
> >
>
> Is the triple dot part of the schema?

Yes. Well, it is part of YAML. It's optional really as are the 2 lines
at the start. It's just good hygiene.

Rob