linux-kernel - Re: [PATCH v3 5/7] dt-bindings: display: Add common rotation property

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Message-ID: <20170206071036.GA27607@ulmo.ba.sec>
Date:   Mon, 6 Feb 2017 08:10:36 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Noralf Trønnes <noralf@...nnes.org>
Cc:     Rob Herring <robh@...nel.org>, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org, thomas.petazzoni@...e-electrons.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/7] dt-bindings: display: Add common rotation property

On Fri, Feb 03, 2017 at 01:16:45PM +0100, Noralf Trønnes wrote:
> Thierry, please have a look at this.
> In which direction should we rotate to match how drm rotation works?
> 
> 
> Den 01.02.2017 18.41, skrev Rob Herring:
> > On Tue, Jan 31, 2017 at 05:03:17PM +0100, Noralf Trønnes wrote:
> > > Display panels can be oriented many ways, especially in the embedded
> > > world. The rotation property is a way to describe this orientation.
> > > The counter clockwise direction is chosen because that's what fbdev
> > > and drm use.
> > The h/w mounting is rotated counter clockwise, so the framebuffers'
> > contents are rotated clockwise, right?

Given that this describes the rotation of the panel, I think it should
be described in terms of how the panel is rotated, not how the
framebuffer needs to be rotated. Using counter-clockwise, as described
in this binding seems fine to me.

It would have to be up to fbdev and DRM/KMS to transform that into a
clockwise rotation for the framebuffer, CRTC, plane, ...

Ideally with some sort of helper.

Thierry

> > 
> > > Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
> > > ---
> > >   Documentation/devicetree/bindings/display/display.txt | 4 ++++
> > This is panel property, so bindings/display/panel/panel.txt.
> > 
> > >   1 file changed, 4 insertions(+)
> > >   create mode 100644 Documentation/devicetree/bindings/display/display.txt
> > > 
> > > diff --git a/Documentation/devicetree/bindings/display/display.txt b/Documentation/devicetree/bindings/display/display.txt
> > > new file mode 100644
> > > index 0000000..e2e6867
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/display/display.txt
> > > @@ -0,0 +1,4 @@
> > > +Common display properties
> > > +-------------------------
> > > +
> > > +- rotation:	Display rotation in degrees counter clockwise (0,90,180,270)
> > > -- 
> > > 2.10.2
> > > 
> > > --
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> 

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