linux-kernel - Re: [RFC PATCH v1 3/3] dt-binding: display: Require two rests on mantix panel

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Message-ID: <20200928150203.GA58525@bogon.m.sigxcpu.org>
Date:   Mon, 28 Sep 2020 17:02:03 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Sam Ravnborg <sam@...nborg.org>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 3/3] dt-binding: display: Require two rests on
 mantix panel

Hi Thierry,
On Mon, Sep 28, 2020 at 08:50:39AM +0200, Thierry Reding wrote:
> On Thu, Sep 24, 2020 at 09:38:07PM +0200, Sam Ravnborg wrote:
> > Hi Guido.
> > 
> > On Mon, Sep 21, 2020 at 06:55:52PM +0200, Guido Günther wrote:
> > > We need to reset both for the panel to show an image.
> > > 
> > > Signed-off-by: Guido Günther <agx@...xcpu.org>
> > > ---
> > >  .../bindings/display/panel/mantix,mlaf057we51-x.yaml       | 7 +++++--
> > >  1 file changed, 5 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.yaml b/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.yaml
> > > index 937323cc9aaa..ba5a18fac9f9 100644
> > > --- a/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.yaml
> > > +++ b/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.yaml
> > > @@ -35,7 +35,9 @@ properties:
> > >    vddi-supply:
> > >      description: 1.8V I/O voltage supply
> > >  
> > > -  reset-gpios: true
> > > +  reset-gpios:
> > > +    minItems: 2
> > > +    maxItems: 2
> > 
> > reset-gpios is, as you already wrote, defined in panel-common.yaml.
> > Do not try to change it here.
> > It would be much better, I think, to introduce a mantix,reset-gpios
> > property.
> > 
> > This would avoid that we had two different reset-gpios definitions.
> 
> My understanding is that this will only override the defaults defined in
> panel-common.yaml. So everything else about the
> panel-common.yaml#/properties/reset-gpios definition remains valid and
> all this does is say that when this matched on "mantix,mlaf057we51-x",
> then the "reset-gpios" property is expected to contain two entries as
> opposed to the single entry that is expected by default.

I thought so too but I get:

linux/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.example.dt.yaml: panel@0: reset-gpios: [[4294967295, 29, 1], [4294967295, 24, 1]] is too long
	From schema: /.../linux/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.yaml

It seems to bepossible to *extend* reset-gpios though because when i use
an example like:

            reset-gpios = <&gpio1 29 GPIO_ACTIVE_LOW>,
                          <&gpio1 24 GPIO_ACTIVE_LOW>;

i correctly get

linux/linux/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.example.dt.yaml: panel@0: reset-gpios: [[4294967295, 29, 1]] is too short
	From schema: /.../linux/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.yaml
 
so the `minItems: 2` is being picked up. This mens i can add
properties but i can't overwrite the existing `maxItems: 2` - that's why
i was wondering how that is supposed to work (if properties should be
overrideable from common files or not).
Cheers,
 -- Guido

> 
> Thierry