DRM_MODE_CONNECTOR_PANEL? [Was: drm/panel: Add and fill drm_panel type field]

Linus Walleij linus.walleij at linaro.org
Fri Sep 27 12:37:42 UTC 2019

Just a drive-by comment:

On Sat, Aug 24, 2019 at 11:54 AM Sam Ravnborg <sam at ravnborg.org> wrote:

> We will also start to see new drivers where there will be support
> for more than one type of connector interface.
> Like for example ili9322:
>  - 8-bit serial RGB interface
>  - 24-bit parallel RGB interface
>  - 8-bit ITU-R BT.601 interface
>  - 8-bit ITU-R BT.656 interface

I just found all these weird references when making the ILI9322 driver
and trying to really understand what was going on in the hardware.
I have this special nack (shared with many kernel developers) that I
need to know what is going on.

I think what is actually the case is that a *lot* of panels that we
support (especially the so-called "simple" panels) are actually complex,
like the ILI9322, just that many of them are undocumented, set up by
ROM or bootloaders, their SPI/I2C lines forgotten about and the
sum result added as a "simple panel" in panel-simple.c.

This is fine I guess to get some basic support up and going,
but all of a sudden someone will use that bridge/panel with
some other input from the list above and ooops wrongly modeled,
the DT compatible string makes no sense etc.

Also the ILI9322 can actually set up gamma correction which is
very nice for professional applications. I haven't seen any way for
DRM to do gamma correction properly or any framework for it
to adjust and propagate gamma to/from userspace (seems like
another enormous task), but I am pretty sure it will be there one
of these days so I put in some comments and placeholders.

Linus Walleij

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