[PATCH 1/3] dt-bindings: display: add bindings for MIPI DBI compatible SPI panels

[Noralf Trønnes]

Den 24.01.2022 17.42, skrev Rob Herring:
> On Mon, Jan 24, 2022 at 10:28 AM Noralf Trønnes <noralf at tronnes.org> wrote:
>>
>>
>>
>> Den 24.01.2022 17.08, skrev Rob Herring:
>>> On Sun, Jan 23, 2022 at 11:25 AM Noralf Trønnes <noralf at tronnes.org> wrote:
>>>>
>>>> Add binding for MIPI DBI compatible SPI panels.
>>>
>>> I'm sure we already have MIPI DBI panels. What's this for?
>>>
>>
>> It aims to use one driver to cover all MIPI DBI panels where the
>> controller setup is loaded from userspace in a firmware file.
> 
> What's the solution when the user wants a splash screen in the
> bootloader and also wants multiple panels supported?
> 

In that case the bootloader needs builtin support for the screen. The OS
driver can then detect that the controller is configured and just skip
the configure stage. I have yet to see someone implement suppport for
such a SPI panel in a bootloader though.

> Also, 1 driver doesn't dictate 1 compatible. A one to many
> relationship is fine and makes the decision entirely the OS's.
> 
>> The cover
>> letter points to the discussion where Maxime proposed this:
>>
>> https://lore.kernel.org/dri-devel/20211129093946.xhp22mvdut3m67sc@houat/
> 
> The proposal there is:
> 
>> compatible = "panel-spi";
>> model = "panel-from-random-place-42";
> 
> The same thing can be accomplished with this:
> 
> compatible = "panel-from-random-place-42", "panel-spi";
> 
> What's the advantage of hijacking 'model'?
> 

That's what Maxime proposed, but having it in the compatible like this
is even better. I suppose it's ok for the driver to use the compatible
to load the firmware file?

Noralf.