linux-kernel - Re: [RFC PATCH 2/2] dt-bindings: pwm: Convert Samsung PWM bindings to json-schema

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Date:   Wed, 18 Sep 2019 13:53:56 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Mark Rutland <mark.rutland@....com>, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Maciej Falkowski <m.falkowski@...sung.com>,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-leds@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] dt-bindings: pwm: Convert Samsung PWM bindings to json-schema

On Fri, 13 Sep 2019 at 16:36, Rob Herring <robh@...nel.org> wrote:
>
> On Mon, Sep 09, 2019 at 08:34:36PM +0200, Krzysztof Kozlowski wrote:
> > Convert Samsung PWM (S3C, S5P and Exynos SoCs) bindings to DT schema
> > format using json-schema.
> >
> > Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
> > ---
> >  .../devicetree/bindings/pwm/pwm-samsung.txt   |  51 --------
> >  .../devicetree/bindings/pwm/pwm-samsung.yaml  | 111 ++++++++++++++++++
> >  2 files changed, 111 insertions(+), 51 deletions(-)
> >  delete mode 100644 Documentation/devicetree/bindings/pwm/pwm-samsung.txt
> >  create mode 100644 Documentation/devicetree/bindings/pwm/pwm-samsung.yaml
>
>
> > diff --git a/Documentation/devicetree/bindings/pwm/pwm-samsung.yaml b/Documentation/devicetree/bindings/pwm/pwm-samsung.yaml
> > new file mode 100644
> > index 000000000000..90fb467bcdd5
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/pwm/pwm-samsung.yaml
> > @@ -0,0 +1,111 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/pwm/pwm-samsung.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Samsung SoC PWM timers
> > +
> > +maintainers:
> > +  - Thierry Reding <thierry.reding@...il.com>
> > +  - Krzysztof Kozlowski <krzk@...nel.org>
> > +
> > +description: |+
> > +  Samsung SoCs contain PWM timer blocks which can be used for system clock source
> > +  and clock event timers, as well as to drive SoC outputs with PWM signal. Each
> > +  PWM timer block provides 5 PWM channels (not all of them can drive physical
> > +  outputs - see SoC and board manual).
> > +
> > +  Be aware that the clocksource driver supports only uniprocessor systems.
> > +
> > +allOf:
> > +  - $ref: pwm.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - samsung,s3c2410-pwm             # 16-bit, S3C24xx
> > +      - samsung,s3c6400-pwm             # 32-bit, S3C64xx
> > +      - samsung,s5p6440-pwm             # 32-bit, S5P64x0
> > +      - samsung,s5pc100-pwm             # 32-bit, S5PC100, S5PV210, Exynos4210 rev0 SoCs
> > +      - samsung,exynos4210-pwm          # 32-bit, Exynos
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    minItems: 1
> > +    maxItems: 3
> > +
> > +  clock-names:
> > +    description: |
> > +      Should contain all following required clock names:
> > +      - "timers" - PWM base clock used to generate PWM signals,
> > +      and any subset of following optional clock names:
> > +      - "pwm-tclk0" - first external PWM clock source,
> > +      - "pwm-tclk1" - second external PWM clock source.
> > +      Note that not all IP variants allow using all external clock sources.
> > +      Refer to SoC documentation to learn which clock source configurations
> > +      are available.
> > +    oneOf:
> > +      - items:
> > +        - const: "timers"
> > +      - items:
> > +        - const: "timers"
> > +        - const: "pwm-tclk0"
> > +      - items:
> > +        - const: "timers"
> > +        - const: "pwm-tclk1"
> > +      - items:
> > +        - const: "timers"
> > +        - const: "pwm-tclk0"
> > +        - const: "pwm-tclk1"
> > +
> > +  interrupts:
> > +    description:
> > +      One interrupt per timer, starting at timer 0.
> > +    minItems: 1
> > +    maxItems: 5
> > +
> > +  "#pwm-cells":
> > +    description:
> > +      The only third cell flag supported by this binding
> > +      is PWM_POLARITY_INVERTED.
> > +    const: 3
> > +
> > +  samsung,pwm-outputs:
> > +    description:
> > +      A list of PWM channels used as PWM outputs on particular platform.
> > +      It is an array of up to 5 elements being indices of PWM channels
> > +      (from 0 to 4), the order does not matter.
> > +    # TODO: Values should not repeat
>
> uniqueItems: true
>
> Though it looks like we have to enable that keyword. (As silently
> ignoring unknown keywords (such as typos) is 'feature' of json-schema,
> we explicitly list keywords we use.)

This works fine.

>
> > +    allOf:
> > +      - $ref: /schemas/types.yaml#/definitions/uint32-array
> > +      # FIXME: min/max limit of items does not work
> > +      - items:
> > +          minItems: 1
> > +          maxItems: 5
> > +      - items:
> > +          minimum: 0
> > +          maximum: 4
>
> I think you want:
>
> minItems: 1
> maxItems: 2
> items:
>   minimum: 0
>   maximum: 4

This not. However I figured out it is not needed. Since these are
unique values from 0 to 4, then the size of array cannot be longer
than 5 or shorter than 1.

Best regards,
Krzysztof