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From:   Krzysztof Kozlowski <krzk@kernel.org>
Date:   Tue, 3 Sep 2019 13:44:20 +0200
Message-ID: <CAJKOXPcjF9nERQxDdSVBLsfc2V_M1_BPZ6iM6EXvEx4tdr3rDQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] dt-bindings: power: syscon-reboot: Convert bindings
 to json-schema
To:     Rob Herring <robh+dt@kernel.org>
Cc:     Sebastian Reichel <sre@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "open list:THERMAL" <linux-pm@vger.kernel.org>,
        devicetree@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, 3 Sep 2019 at 11:00, Rob Herring <robh+dt@kernel.org> wrote:
>
> On Tue, Sep 3, 2019 at 8:47 AM Krzysztof Kozlowski <krzk@kernel.org> wrote:
> >
> > On Tue, 3 Sep 2019 at 09:14, Rob Herring <robh+dt@kernel.org> wrote:
> > >
> > > On Mon, Sep 2, 2019 at 4:03 PM Krzysztof Kozlowski <krzk@kernel.org> wrote:
> > > >
> > > > Convert the Syscon reboot bindings to DT schema format using
> > > > json-schema.
> > > >
> > > > Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
> > > > ---
> > > >  .../bindings/power/reset/syscon-reboot.txt    | 30 --------
> > > >  .../bindings/power/reset/syscon-reboot.yaml   | 68 +++++++++++++++++++
> > > >  2 files changed, 68 insertions(+), 30 deletions(-)
> > > >  delete mode 100644 Documentation/devicetree/bindings/power/reset/syscon-reboot.txt
> > > >  create mode 100644 Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml
> > >
> > > > diff --git a/Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml b/Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml
> > > > new file mode 100644
> > > > index 000000000000..a583f3dc8ef4
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml
> > > > @@ -0,0 +1,68 @@
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/power/reset/syscon-reboot.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Generic SYSCON mapped register reset driver
> > > > +
> > > > +maintainers:
> > > > +  - Sebastian Reichel <sre@kernel.org>
> > > > +
> > > > +description: |+
> > > > +  This is a generic reset driver using syscon to map the reset register.
> > > > +  The reset is generally performed with a write to the reset register
> > > > +  defined by the register map pointed by syscon reference plus the offset
> > > > +  with the value and mask defined in the reboot node.
> > > > +  Default will be little endian mode, 32 bit access only.
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    const: syscon-reboot
> > > > +
> > > > +  mask:
> > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > +    description: Update only the register bits defined by the mask (32 bit).
> > > > +    maxItems: 1
> > >
> > > Drop this as that is already defined for uint32.
> > >
> > > It also doesn't actually work. The $ref has to be under an 'allOf' if
> > > you have additional schemas. A quirk of json-schema...
> > >
> > > > +
> > > > +  offset:
> > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > +    description: Offset in the register map for the reboot register (in bytes).
> > > > +    maxItems: 1
> > > > +
> > > > +  regmap:
> > > > +    $ref: /schemas/types.yaml#/definitions/phandle
> > > > +    description: Phandle to the register map node.
> > > > +    maxItems: 1
> > > > +
> > > > +  value:
> > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > +    description: The reset value written to the reboot register (32 bit access).
> > > > +    maxItems: 1
> > > > +
> > > > +required:
> > > > +  - compatible
> > > > +  - regmap
> > > > +  - offset
> > > > +
> > > > +allOf:
> > > > +  - if:
> > > > +      properties:
> > > > +        value:
> > > > +          not:
> > > > +            type: array
> > >
> > > I think you could make this a bit more readable with:
> > >
> > > if:
> > >   not:
> > >     required:
> > >       - value
> >
> > I do not understand how does it work (value is not mentioned in the
> > required fields so why checking of it?)... but it works fine.
>
> What's under required doesn't have to be listed as a property.
>
> > > However, if the tree is free of legacy usage, then you could just drop all this.
> >
> > One of them - mask or value - has to be provided.
>
> Or both, right?
>
> Actually, a better way to express it is probably this:
>
> oneOf:
>   - required: [ value ]
>   - required: [ mask ]
>   - required: [ value, mask ]

This does not work mask+value would be valid everywhere:

arch/arm/boot/dts/exynos3250-artik5-eval.dt.yaml: syscon-reboot:
{'regmap': [[9]], 'mask': [[1]], '$nodename': ['syscon-reboot'],
'value': [[1]], 'offset': [[1024]], 'compatible': ['syscon-reboot']}
is valid under each of {'required': ['mask']}, {'required': ['value',
'mask']}, {'required': ['value']}