Re: [PATCH v7 10/11] ARM: at91/dt: add LCD panel description to sama5d3xdm.dtsi

From: Thierry Reding <thierry.reding@gmail.com>
To: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	linux-pwm@vger.kernel.org, devicetree@vger.kernel.org,
	Samuel Ortiz <sameo@linux.intel.com>,
	Pawel Moll <pawel.moll@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Lee Jones <lee.jones@linaro.org>,
	Nicolas Ferre <nicolas.ferre@atmel.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Rob Herring <robh+dt@kernel.org>,
	Alexandre Belloni <alexandre.belloni@free-electrons.com>,
	Kumar Gala <galak@codeaurora.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
	Andrew Victor <linux@maxim.org.za>,
	linux-arm-kernel@lists.infradead.org,
	Mark Yao <mark.yao@rock-chips.com>
Subject: Re: [PATCH v7 10/11] ARM: at91/dt: add LCD panel description to sama5d3xdm.dtsi
Date: Mon, 6 Oct 2014 14:40:15 +0200	[thread overview]
Message-ID: <20141006124014.GD26833@ulmo> (raw)
In-Reply-To: <20141006142538.76d2df29@bbrezillon>

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On Mon, Oct 06, 2014 at 02:25:38PM +0200, Boris Brezillon wrote:
> On Mon, 6 Oct 2014 13:01:16 +0200 Thierry Reding <thierry.reding@gmail.com> wrote:
> > On Wed, Oct 01, 2014 at 04:53:07PM +0200, Boris Brezillon wrote:
> > [...]
> > > diff --git a/arch/arm/boot/dts/sama5d3xdm.dtsi b/arch/arm/boot/dts/sama5d3xdm.dtsi
[...]
> > > +		backlight = <&backlight>;
> > > +		power-supply = <&panel_reg>;
> > > +		#address-cells = <1>;
> > > +		#size-cells = <0>;
> > > +		status = "disabled";
> > > +
> > > +		port@0 {
> > > +			#address-cells = <1>;
> > > +			#size-cells = <0>;
> > > +
> > > +			panel_input: endpoint@0 {
> > > +				reg = <0>;
> > > +				remote-endpoint = <&hlcdc_panel_output>;
> > > +			};
> > >  		};
> > 
> > There's no support for OF graphs in simple-panel, so this is unused,
> > isn't it?
> 
> Actually I use it in my atmel_hlcdc_ouput implementation to figure out
> the link between a panel and a device connected on the RGB/DPI bus. 

That's kind of weird and one of the reasons why I can't make myself like
the OF graph bindings. It requires drivers for one device to reach into
the device tree node of some other device and look for content. Or put
another way, a DT node for a panel that works on one platform doesn't
work on another because the display controller needs additional DT
content that isn't required by the original binding for the panel.

Thierry

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