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

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Date:   Tue, 7 Feb 2017 16:34:44 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Noralf Trønnes <noralf@...nnes.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 0/2] drm/panel: Add support for the Sitronix ST7789V

On Mon, Feb 06, 2017 at 12:29:31PM +0100, Noralf Trønnes wrote:
> 
> Den 06.02.2017 11.39, skrev Maxime Ripard:
> > Hi Noralf,
> > 
> > On Fri, Feb 03, 2017 at 07:48:51PM +0100, Noralf Trønnes wrote:
> > > Den 03.02.2017 10.59, skrev Maxime Ripard:
> > > > 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?
> > 
> > > 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.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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