linux-kernel - Re: [PATCH v2 1/3] dt-bindings: display: add new bus-format property for panel-dpi

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Date:   Tue, 28 Jun 2022 19:54:06 +0200
From:   Max Krummenacher <max.oss.09@...il.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Max Krummenacher <max.krummenacher@...adex.com>,
        Marek Vasut <marex@...x.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Francesco Dolcini <francesco.dolcini@...adex.com>,
        Maxime Ripard <mripard@...nel.org>,
        Christoph Niedermaier <cniedermaier@...electronics.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Thierry Reding <thierry.reding@...il.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: display: add new bus-format property
 for panel-dpi

Hi Rob

Thanks for the feedback.

On Wed, Jun 1, 2022 at 10:17 PM Rob Herring <robh@...nel.org> wrote:
>
> On Wed, May 18, 2022 at 01:55:38PM +0200, Max Krummenacher wrote:
> > From: Max Krummenacher <max.krummenacher@...adex.com>
> >
> > The property is used to set the enum bus_format and infer the bpc
> > for a panel defined by 'panel-dpi'.
> > This specifies how the panel is connected to the display interface.
> >
> > Signed-off-by: Max Krummenacher <max.krummenacher@...adex.com>
> >
> > ---
> >
> > Changes in v2:
> >     - Fix errors found by dt_binding_check
> >
> >  .../bindings/display/panel/panel-dpi.yaml     | 11 +++++++++
> >  .../dt-bindings/display/dt-media-bus-format.h | 23 +++++++++++++++++++
> >  2 files changed, 34 insertions(+)
> >  create mode 100644 include/dt-bindings/display/dt-media-bus-format.h
> >
> > diff --git a/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> > index dae0676b5c6e..a20b5898941e 100644
> > --- a/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> > +++ b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> > @@ -21,6 +21,14 @@ properties:
> >        - {}
> >        - const: panel-dpi
> >
> > +  bus-format:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
>
> Constraints?

Will limit the range to the one used for RGB formats in v3.
>
> > +    description: |
> > +      Describes how the display panel is connected to the display interface.
> > +      Valid values are defined in <dt-bindings/display/dt-media-bus-format.h>.
> > +      The mapping between the color/significance of the panel lines to the
> > +      parallel data lines are defined in [1].
>
> Just drop the [1] and use a colon.

Done in v3.

>
> > +      [1] https://www.kernel.org/doc/html/v5.17/userspace-api/media/v4l/subdev-formats.html#packed-rgb-formats
>
> Why not just use the V4L number space rather than invent yet another
> number space?

That was a proposal from here:
https://lore.kernel.org/all/20220323155817.xcsqxothziot7ba3@houat/
But probably it makes more sense to use the number space as is, changed in v3.

>
> Need a blank line here too.
>
> >    backlight: true
> >    enable-gpios: true
> >    height-mm: true
> > @@ -39,11 +47,14 @@ additionalProperties: false
> >
> >  examples:
> >    - |
> > +    #include <dt-bindings/display/dt-media-bus-format.h>
> > +
> >      panel {
> >          compatible = "startek,startek-kd050c", "panel-dpi";
> >          label = "osddisplay";
> >          power-supply = <&vcc_supply>;
> >          backlight = <&backlight>;
> > +        bus-format = <DT_MEDIA_BUS_FMT_RGB888_1X24>;
>
> Other properties describing the interface have been put in the endpoint
> node. This should too I think.

That makes a lot of sense. Changed to be part of the endpoint node in v3.

Cheers
Max

>
> >
> >          port {
> >              lcd_in: endpoint {
> > diff --git a/include/dt-bindings/display/dt-media-bus-format.h b/include/dt-bindings/display/dt-media-bus-format.h
> > new file mode 100644
> > index 000000000000..c0f2a7b59aa1
> > --- /dev/null
> > +++ b/include/dt-bindings/display/dt-media-bus-format.h
> > @@ -0,0 +1,23 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
> > +/*
> > + * Copyright 2022 Max Krummenacher <max.krummenacher@...adex.com>
> > + */
> > +
> > +#ifndef __DT_BINDINGS_DT_MEDIA_BUS_FORMAT_H
> > +#define __DT_BINDINGS_DT_MEDIA_BUS_FORMAT_H
> > +
> > +/*
> > + * Attention: Keep these macro names in sync with
> > + * include/uapi/linux/media-bus-format.h
> > + */
> > +
> > +#define DT_MEDIA_BUS_FMT_RGB565_1X16         1
> > +#define DT_MEDIA_BUS_FMT_RGB666_1X18         2
> > +#define DT_MEDIA_BUS_FMT_RBG888_1X24         3
> > +#define DT_MEDIA_BUS_FMT_RGB666_1X24_CPADHI  4
> > +#define DT_MEDIA_BUS_FMT_BGR888_1X24         5
> > +#define DT_MEDIA_BUS_FMT_GBR888_1X24         6
> > +#define DT_MEDIA_BUS_FMT_RGB888_1X24         7
> > +#define DT_MEDIA_BUS_FMT_RGB888_1X32_PADHI   8
> > +
> > +#endif /* __DT_BINDINGS_DT_MEDIA_BUS_FORMAT_H */
> > --
> > 2.20.1
> >
> >