linux-kernel - Re: [PATCH v3 2/4] spi: dt-bindings: samsung: convert to dtschema

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Message-ID: <20220120092459.gbaoief77p2tynaf@krzk-bin>
Date:   Thu, 20 Jan 2022 10:24:59 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Pratyush Yadav <p.yadav@...com>
Cc:     Andi Shyti <andi@...zian.org>, Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, linux-spi@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Sam Protsenko <semen.protsenko@...aro.org>
Subject: Re: [PATCH v3 2/4] spi: dt-bindings: samsung: convert to dtschema

On Thu, Jan 20, 2022 at 02:30:02PM +0530, Pratyush Yadav wrote:
> On 20/01/22 08:36AM, Krzysztof Kozlowski wrote:
> > On 20/01/2022 08:06, Pratyush Yadav wrote:
> > > On 19/01/22 08:49PM, Krzysztof Kozlowski wrote:
> > >> On 19/01/2022 20:31, Pratyush Yadav wrote:
> > >>> On 12/01/22 11:00AM, Krzysztof Kozlowski wrote:
> > >>>> Convert the Samsung SoC (S3C24xx, S3C64xx, S5Pv210, Exynos) SPI
> > >>>> controller bindings to DT schema format
> > >>>>
> > >>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
> > >>>> Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>
> > >>>> ---
> > >>>>  .../spi/samsung,spi-peripheral-props.yaml     |  35 ++++
> > >>>>  .../devicetree/bindings/spi/samsung,spi.yaml  | 187 ++++++++++++++++++
> > >>>>  .../bindings/spi/spi-peripheral-props.yaml    |   1 +
> > >>>>  .../devicetree/bindings/spi/spi-samsung.txt   | 122 ------------
> > >>>>  MAINTAINERS                                   |   2 +-
> > >>>>  5 files changed, 224 insertions(+), 123 deletions(-)
> > >>>>  create mode 100644 Documentation/devicetree/bindings/spi/samsung,spi-peripheral-props.yaml
> > >>>>  create mode 100644 Documentation/devicetree/bindings/spi/samsung,spi.yaml
> > >>>>  delete mode 100644 Documentation/devicetree/bindings/spi/spi-samsung.txt
> > >>>>
> > >>>> diff --git a/Documentation/devicetree/bindings/spi/samsung,spi-peripheral-props.yaml b/Documentation/devicetree/bindings/spi/samsung,spi-peripheral-props.yaml
> > >>>> new file mode 100644
> > >>>> index 000000000000..aa5a1f48494b
> > >>>> --- /dev/null
> > >>>> +++ b/Documentation/devicetree/bindings/spi/samsung,spi-peripheral-props.yaml
> > >>>> @@ -0,0 +1,35 @@
> > >>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > >>>> +%YAML 1.2
> > >>>> +---
> > >>>> +$id: http://devicetree.org/schemas/spi/samsung,spi-peripheral-props.yaml#
> > >>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > >>>> +
> > >>>> +title: Peripheral-specific properties for Samsung S3C/S5P/Exynos SoC SPI controller
> > >>>> +
> > >>>> +maintainers:
> > >>>> +  - Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
> > >>>> +
> > >>>> +description:
> > >>>> +  See spi-peripheral-props.yaml for more info.
> > >>>> +
> > >>>> +properties:
> > >>>> +  controller-data:
> > >>>> +    type: object
> > >>>> +    additionalProperties: false
> > >>>> +
> > >>>> +    properties:
> > >>>> +      samsung,spi-feedback-delay:
> > >>>> +        description: |
> > >>>> +          The sampling phase shift to be applied on the miso line (to account
> > >>>> +          for any lag in the miso line). Valid values:
> > >>>> +           - 0: No phase shift.
> > >>>> +           - 1: 90 degree phase shift sampling.
> > >>>> +           - 2: 180 degree phase shift sampling.
> > >>>> +           - 3: 270 degree phase shift sampling.
> > >>>> +        $ref: /schemas/types.yaml#/definitions/uint32
> > >>>> +        enum: [0, 1, 2, 3]
> > >>>> +
> > >>>> +    required:
> > >>>> +      - samsung,spi-feedback-delay
> > >>>
> > >>> I am not quite sure if this required would work here. Let's say another 
> > >>> controller also uses a controller-data node, but it contains a different 
> > >>> set of properties. Won't this cause an error to be raised for that 
> > >>> controller since this property is not there?
> > >>
> > >> The controller-data is Samsung SPI specific (does not exist in any other
> > >> binding), so why would controller-data get added to a different controller?
> > > 
> > > It does not as of now, but the name is fairly generic and some 
> > > controller in the future might use it. I do not think it is a good idea 
> > > to list required properties in X-peripheral-props.yaml in general since 
> > > all those will be collected by spi-peripheral-props.yaml and so will 
> > > apply to _all_ controllers that reference it.
> > 
> > Right, but have in mind this is merely a bindings conversion. These were
> > made like this long time ago.
> 
> Yes, but the bindings infrastructure is not capable of handling these 
> required properties as of now. So even if your next patch was _not_ 
> making it optional, I would still say you should drop the "required:". 
> Even though the property is actually a required one, we currently do not 
> have the means to express that.
> 
> > 
> > I think we can drop the "required:" entirely with the commit 3/4 which
> > makes it optional.
> 
> I would prefer you never add it in the first place.

If I understand correctly, you propose to squash next patch making it
optional to this conversion? I believe there is a value in splitting
conversion of existing bindings from making changes to the bindings, but
I don't mind squashing them if that is desired.

Best regards,
Krzysztof