Re: [PATCH v3 1/4] drm: bridge: dw_hdmi: Add flag to indicate output port is optional

[Marek Vasut <marex@denx.de>]

On 12/31/24 9:31 PM, Laurent Pinchart wrote:
> Hi Marek,

Hi,

> Thank you for the patch.
> 
> On Tue, Dec 31, 2024 at 08:28:48PM +0100, Marek Vasut wrote:
>> Add a flag meant purely to work around broken i.MX8MP DTs which enable
>> HDMI but do not contain the HDMI connector node. This flag allows such
>> DTs to work by creating the connector in the HDMI bridge driver. Do not
>> use this flag, do not proliferate this flag, please fix your DTs.
> 
> What's the rationale for this, what prevents fixing DT instead of using
> this flag ? Adding such a flag will most likely open the door to
> proliferation.

See the V2 series discussion, there are a few in-tree DTs which do not 
have the HDMI connector node. The rationale is there might be more and 
they might come from vendors, so this flag is necessary to work around 
those DTs.

> If you can't fix the DT on particular boards, patching it could be an
> option. We had a similar problem on Renesas boards, which we fixed with
> a DT overlay, see commit 81c0e3dd82927064 ("drm: rcar-du: Fix legacy DT
> to create LVDS encoder nodes"). This made the workaround self-contained,
> and allowed dropping it several kernel versions later (in commit
> 841281fe52a769fe, "drm: rcar-du: Drop LVDS device tree backward
> compatibility").
Frankly, I would much rather fix the few in-tree DTs and mandate the 
HDMI connector node in DT, which would keep the code simple, rather than 
maintain a backward compatibility workaround for problem which might not 
even exist.