linux-kernel - Re: [PATCH v2 2/2] drm/panel: simple: Add support for ddc-only panel

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Date:   Fri, 14 Jul 2017 09:15:47 -0500
From:   Rob Herring <robh@...nel.org>
To:     linux-kernel-dev@...khoff.com
Cc:     Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>,
        Patrick Bruenn <p.bruenn@...khoff.com>
Subject: Re: [PATCH v2 2/2] drm/panel: simple: Add support for ddc-only panel

On Thu, Jul 13, 2017 at 6:04 AM,  <linux-kernel-dev@...khoff.com> wrote:
> From: Patrick Bruenn <p.bruenn@...khoff.com>
>
> This is a fix for the CX9020 Embedded PC. On that device the 24-bit
> parallel-display signal of the imx53 is combined with an I2C channel
> and converted to DVI-D port. Devicetree magic always requires a panel
> connected to the parallel-display port.

Then fix this. It's not the DT that requires this, but limitations in
the i.MX driver.

> We add an empty panel_desc, to get recognized by the panel-simple
> driver, which can then use the ddc bus to read the panels configuration.
>
> Signed-off-by: Patrick Bruenn <p.bruenn@...khoff.com>
> ---
>  drivers/gpu/drm/panel/panel-simple.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index c4566ce8fda7..52b2a7fb59ed 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -1856,6 +1856,9 @@ static const struct panel_desc winstar_wf35ltiacd = {
>         .bus_format = MEDIA_BUS_FMT_RGB888_1X24,
>  };
>
> +static const struct panel_desc simple_ddc_only = {
> +};
> +
>  static const struct of_device_id platform_of_match[] = {
>         {
>                 .compatible = "ampire,am-480272h3tmqw-t01h",
> @@ -2050,6 +2053,9 @@ static const struct of_device_id platform_of_match[] = {
>                 .compatible = "winstar,wf35ltiacd",
>                 .data = &winstar_wf35ltiacd,
>         }, {
> +               .compatible = "simple,ddc-only",

If you notice the rest of the file, we require compatibles be specific
for the panels.

What you want here is a "dvi-connector" node.

Rob