linux-kernel - Re: [PATCH v2 2/5] dt-bindings: display: ssd1307fb: Extend schema for SPI controllers

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Date:   Tue, 12 Apr 2022 10:07:25 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh@...nel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Mark Brown <broonie@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Chen-Yu Tsai <wens@...nel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/5] dt-bindings: display: ssd1307fb: Extend schema for
 SPI controllers

Hi Javier,

On Tue, Apr 12, 2022 at 10:01 AM Javier Martinez Canillas
<javierm@...hat.com> wrote:
> On 4/12/22 09:16, Geert Uytterhoeven wrote:
> > On Mon, Apr 11, 2022 at 11:12 PM Javier Martinez Canillas
> > <javierm@...hat.com> wrote:
> >> The Solomon SSD130x OLED displays can either have an I2C or SPI interface,
> >> add to the schema the properties and examples for OLED devices under SPI.
> >>
> >> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>

> >> --- a/Documentation/devicetree/bindings/display/solomon,ssd1307fb.yaml
> >> +++ b/Documentation/devicetree/bindings/display/solomon,ssd1307fb.yaml
> >> @@ -39,9 +39,14 @@ properties:
> >>    reset-gpios:
> >>      maxItems: 1
> >>
> >> +  dc-gpios:
> >> +    maxItems: 1
> >> +
> >
> > Perhaps add a description, and clarify this is for SPI only?
>
> I wondered how to make it required for SPI but couldn't find another binding
> that did the same and I'm not that familiar with DT schemas to figure it out.
>
> Before, when I had compatible strings just for SPI I could do the following:
>
>   - if:
>       properties:
>         compatible:
>           contains:
>             enum:
>               - sinowealth,sh1106-spi
>               - solomon,ssd1305-spi
>               - solomon,ssd1306-spi
>               - solomon,ssd1307-spi
>               - solomon,ssd1309-spi
>     then:
>       required:
>         - spi-max-frequency
>         - dc-gpios
>
> but now that we are using the same compatible strings for I2C and SPI, the
> compatible string can't be used anymore as an indication to make required.
>
> Do you have any hints here on how I should enforce this in the schema ?
>
> Or if you think that a comment is enough, then I will add it in v3.

I don't know how to make it required for SPI, if possible at all.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds