Re: [PATCH 7/8] drm/bridge: imx8mp-hdmi-tx: add an hdmi-connector when missing using a DT overlay at boot time

Luca Ceresoli
2026-04-01T07:51:50Z

Hello Liu,

On Wed Apr 1, 2026 at 8:45 AM CEST, Liu Ying wrote:
>>>>>> Boards with a different connector should describe the connector in the
>>>>>> device tree, if they need to instantiate the exact type.
>>>>
>>>> I think this is the only valid solution. It's very easy to do, nothing new
>>>> to invent.
>>>>
>>>> Maybe on top of that we could add a warning when the overlay is applied,
>>>> e.g. "imx8mp-hdmi-tx used without a connector described in device tree;
>>>> adding a type A connector as a fallback; please add a valid description to
>>>> your device tree".
>>>
>>> I'd say this doesn't sound a bad idea but I hope the message is clear and
>>> short.
>>
>> What about:
>>
>> Connector description not found in device tree, please add one. Falling back to Type A.
>
> Maybe:
> Please add a hdmi-connector DT node for imx8mp-hdmi-tx. A fixup node in type a is added for now.
>
>>
>>>> Maybe pointing to a TODO entry in the documentation.
>>>
>>> To parameterize the HDMI connector type? If so, I'm okay with that.
>>
>> I was meaning a TODO entry to suggest people to add a connector description
>> to the dts. E.g., expanding on the above suggested warning:
>>
>> Connector description not found in device tree, please add one. See https://docs.kernel.org/gpu/todo.html#<...>
>>
>> And of course adding a TODO entry describing what one needs to do (add an
>> hdmi-connector node and link it to port@1 of the hdmi-tx).
>>
>> The drawback of the TODO is that items in todo.rst are supposed to be
>> removed eventually when done in the code, but this one cannot be removed
>> until some kernels printing the above logging message will be around,
>> i.e. potentially for decades.
>
> Not a big fan of adding a TODO entry, because those DT blobs without a
> hdmi-connector node could be out there forever, meaning the added TODO
> entry can never be removed.
>
>>
>> So maybe the simplest solution is just the first warning message + a
>> comment in the code right before the warning line, so it easily found with
>> grep or a web search by who sees the warning.
>
> +1.

Agreed. I've already sent v2, so I'll queue this for v3.

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering