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

[Rob Herring]

On Thu, Jan 27, 2022 at 3:36 AM Maxime Ripard <maxime at cerno.tech> wrote:
>
> Hi Rob,
>
> On Mon, Jan 24, 2022 at 10:42:37AM -0600, Rob Herring wrote:
> > 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?
> >
> > 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'?
>
> So, the main issue is that a panel is essentially two things: a
> controller and the actual panel.
>
> The controller has an initialization sequence of its own, and part of it
> is parameters to match the panel.
>
> So you can have identical controllers that won't have the same
> initialization sequence because they don't have the same panel.
>
> I was assuming that a compatible would be more about the controller, so
> we needed something else, thus "model"

We already have cases like that which have "foo,some-panel", "bar,a-ctrlr-ic".

Rob