[RFC][PATCH 2/3] drm/modes: Make width-mm/height-mm mandatory in of_get_drm_panel_display_mode()

[Marek Vasut]

On 4/2/22 09:45, Noralf Trønnes wrote:
> 
> 
> Den 02.04.2022 06.28, skrev Marek Vasut:
>> On 4/2/22 05:19, Laurent Pinchart wrote:
>>> On Fri, Apr 01, 2022 at 10:36:24PM +0200, Marek Vasut wrote:
>>>> On 4/1/22 20:46, Laurent Pinchart wrote:
>>>>> On Fri, Apr 01, 2022 at 06:37:54PM +0200, Marek Vasut wrote:
>>>>>> Make the width-mm/height-mm panel properties mandatory in
>>>>>> of_get_drm_panel_display_mode(), print error message and
>>>>>> return -ve in case these DT properties are not present.
>>>>>> This is needed to correctly report panel dimensions.
>>>>>
>>>>> Can we guarantee this won't cause a regression ?
>>>>
>>>> For the upstream DTs, I think we can.
>>>> For downstream DTs, we cannot know.
>>>
>>> Are there users of this function whose DT bindings don't require the
>>> width-mm and height-mm properties ?
>>
>> There is literally one user of this function upstream:
>> drivers/gpu/drm/tiny/panel-mipi-dbi.c
> 
> Yes, the function was added for that driver since it was so generic in
> nature. What about adding an argument to of_get_drm_panel_display_mode()
> that tells if the properties are mandatory or not?

Sure, we can do that, but maybe the question here is even bigger than 
this series.

Should every panel set mandatory width_mm/height_mm so e.g. the user 
space can infer DPI from it and set up scaling accordingly, or should 
width_mm/height_mm be optional ?

I think width_mm/height_mm should be mandatory for all panels.

Thoughts ?