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Date:   Sun, 7 May 2023 10:50:45 +0100
From:   Andre Przywara <andre.przywara@arm.com>
To:     Icenowy Zheng <icenowy@aosc.io>
Cc:     Maksim Kiselev <bigunclemax@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Cristian Ciocaltea <cristian.ciocaltea@collabora.com>,
        Maxime Ripard <mripard@kernel.org>, linux-spi@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org
Subject: Re: [PATCH v3 1/5] dt-bindings: spi: sun6i: add DT bindings for
 Allwinner R329/D1/R528/T113s SPI
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On Sun, 07 May 2023 12:06:58 +0800
Icenowy Zheng <icenowy@aosc.io> wrote:

Hi,

> 在 2023-05-07星期日的 02:26 +0300，Maksim Kiselev写道：
> > Listed above Allwinner SoCs has two SPI controllers. First is the
> > regular
> > SPI controller and the second one has additional functionality for
> > MIPI-DBI Type C.
> > 
> > Add compatible strings for these controllers
> > 
> > Signed-off-by: Maksim Kiselev <bigunclemax@gmail.com>
> > ---
> >  .../devicetree/bindings/spi/allwinner,sun6i-a31-spi.yaml   | 7
> > +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/spi/allwinner,sun6i-
> > a31-spi.yaml b/Documentation/devicetree/bindings/spi/allwinner,sun6i-
> > a31-spi.yaml
> > index de36c6a34a0f..807dde457e3b 100644
> > --- a/Documentation/devicetree/bindings/spi/allwinner,sun6i-a31-
> > spi.yaml
> > +++ b/Documentation/devicetree/bindings/spi/allwinner,sun6i-a31-
> > spi.yaml
> > @@ -21,6 +21,7 @@ properties:
> >      oneOf:
> >        - const: allwinner,sun6i-a31-spi
> >        - const: allwinner,sun8i-h3-spi
> > +      - const: allwinner,sun50i-r329-spi
> >        - items:
> >            - enum:
> >                - allwinner,sun8i-r40-spi
> > @@ -28,6 +29,12 @@ properties:
> >                - allwinner,sun50i-h616-spi
> >                - allwinner,suniv-f1c100s-spi
> >            - const: allwinner,sun8i-h3-spi
> > +      - items:
> > +          - enum:
> > +              - allwinner,sun20i-d1-spi
> > +              - allwinner,sun20i-d1-spi-dbi  

This construct doesn't cover the three compatible string case, since we
only get to choose from one of the enums, and always have two strings -
hence my challenge to find the shortest sequence ;-)

> In this case I will prefer to list all 4 compatibles if backward
> compatibility is used:
> "allwinner,sun20i-d1-spi-dbi", "allwinner-sun20i-d1-spi",
> "allwinner,sun50i-r329-spi-dbi", "allwinner, sun50i-r329-spi", in case
> if we were gaining support for either quirks of D1 controller or
> SPI_DBI controllers.

I see where you are coming from, but that order doesn't look right,
since we go back from DBI to normal and then back again. And
"allwinner-sun20i-d1-spi" is not a super set of
"allwinner,sun50i-r329-spi-dbi".
In case we will need a D1 quirk, we could key this to the D1 DBI
compatible as well, I think, so this three string version should work.

Cheers,
Andre

> 
> > +              - allwinner,sun50i-r329-spi-dbi
> > +          - const: allwinner,sun50i-r329-spi
> >  
> >    reg:
> >      maxItems: 1  
>