Re: [PATCH 0/2] drm/panel: Add support for the Sitronix ST7789V

On Tue, Feb 07, 2017 at 04:34:44PM +0100, Maxime Ripard wrote:

On Mon, Feb 06, 2017 at 12:29:31PM +0100, Noralf Trønnes wrote:

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Den 06.02.2017 11.39, skrev Maxime Ripard:

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Hi Noralf,

On Fri, Feb 03, 2017 at 07:48:51PM +0100, Noralf Trønnes wrote:

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Den 03.02.2017 10.59, skrev Maxime Ripard:

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Hi,

Here is an attempt at supporting the ST7789V LCD controller from Sitronix.

What happens if there's another panel driven by ST7789V that needs
a different controller initialization?

You know those panels / controllers much better than I do, but why
would that be the case?

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Maybe it's better to name it after the panel, not the controller.

I guess you could also use that panel directly without the controller?

A controller can drive many different panels that can require different
initializations. I faced that with staging/fbtft, when I wrote
controller drivers having initialization code, and then came across
displays with the same controller but with a different initialization.

Trying to write controller drivers for these controllers is very
difficult with all the possible permutations. On top of that we have
those undocumented commands/registers.

Some panels come with embedded controllers, in which case it makes
sense to write a driver for the panel.

But if the panel and controller are separate, then I don't know. Maybe
the chance of coming across two uncompatible ST7789V and panel
combinations in drm/panel is extremly low.

Hmm, I see. If we ever come across that case, I guess we could just
add new optional properties to override the current sequence.

I think if that ever happens it's probably best to split out ST7789V
code into a helper library that has functions which take parameters.
Then we can simply call those functions with parameters specific to
a panel from a panel-specific driver.

Trying to fit all that into device tree properties is likely going to
end up being really messy.

Thierry