Re: [PATCH 10/54] dt-bindings: display: panel-lvds: Document panel compatibles

Maxime Ripard
2021-08-23T16:33:26Z

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Hi,

On Wed, Aug 18, 2021 at 08:48:46AM -0500, Rob Herring wrote:
> On Wed, Aug 18, 2021 at 7:43 AM Maxime Ripard <maxime@cerno.tech> wrote:
> >
> > Hi Rob, Sam,
> >
> > On Wed, Jul 21, 2021 at 08:29:47PM -0600, Rob Herring wrote:
> > > On Wed, Jul 21, 2021 at 04:03:40PM +0200, Maxime Ripard wrote:
> > > > The binding mentions that all the drivers using that driver must use a
> > > > vendor-specific compatible but never enforces it, nor documents the
> > > > vendor-specific compatibles.
> > > >
> > > > Let's make we document all of them, and that the binding will create an
> > > > error if we add one that isn't.
> > > >
> > > > Cc: dri-devel@lists.freedesktop.org
> > > > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > > Cc: Sam Ravnborg <sam@ravnborg.org>
> > > > Cc: Thierry Reding <thierry.reding@gmail.com>
> > > > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> > > > ---
> > > > .../bindings/display/panel/lvds.yaml | 18 ++++++++++++------
> > > > 1 file changed, 12 insertions(+), 6 deletions(-)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/panel/lvds.yaml b/Documentation/devicetree/bindings/display/panel/lvds.yaml
> > > > index 49460c9dceea..d1513111eb48 100644
> > > > --- a/Documentation/devicetree/bindings/display/panel/lvds.yaml
> > > > +++ b/Documentation/devicetree/bindings/display/panel/lvds.yaml
> > > > @@ -31,12 +31,18 @@ allOf:
> > > >
> > > > properties:
> > > > compatible:
> > > > - contains:
> > > > - const: panel-lvds
> > > > - description:
> > > > - Shall contain "panel-lvds" in addition to a mandatory panel-specific
> > > > - compatible string defined in individual panel bindings. The "panel-lvds"
> > > > - value shall never be used on its own.
> > > > + items:
> > > > + - enum:
> > > > + - advantech,idk-1110wr
> > >
> > > At least this one is documented elsewhere.
> >
> > Indeed, I missed it.
> >
> > > You can add 'minItems: 2' if you want to just enforce having 2 compatibles. Or do:
> > >
> > > items:
> > > - {}
> > > - const: panel-lvds
> > >
> > > Which also enforces the order.
> >
> > It's not just about the order since a missing compatible will also raise
> > a warning.
> >
> > Some of those panels have a binding of their own, but some probably
> > won't (and I can't find anything specific about the one I'm most
> > interested in: tbs,a711-panel)
> >
> > Can we have something like:
> >
> > compatible:
> > oneOf:
> > - items:
> > - enum:
> > - tbs,a711-panel
> > - const: panel-lvds
> >
> > - items:
> > - {}
> > - const: panel-lvds
> >
> > That would work for both cases I guess?
>
> No, both conditions will be true. If you use 'anyOf', then we're never
> really checking the specific compatible.
>
> I think the problem here is trying to mix a common binding (aka an
> incomplete collection of properties) and a specific binding.

I'm not entirely sure why we have specific bindings for this in the
first place.

We currently have 6 specific bindings, and for 5 of them the only
specific thing in there are the data-mapping value to force and their
dimension.

I'd argue that the dimension shouldn't even be set in stone: you could
very well imagine a screen with exactly the same timings but a different
size. We would consider it compatible.

And the data-mapping can be dealt with with an if clause fairly easily.

And for the last one, the specific thing about it is that it's using a
dual-link output, which is a generic binding and could thus be described
in panel-lvds too.

Maxime

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