From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sascha Hauer Subject: Re: Best practice device tree design for display subsystems/DRM Date: Thu, 4 Jul 2013 11:57:59 +0200 Message-ID: <20130704095759.GK10414@pengutronix.de> References: <51D348F5.2080205@gmail.com> <00ae01ce77cb$524d57f0$f6e807d0$%dae@samsung.com> <20130703090242.GM516@pengutronix.de> <20130703095248.GG13924@flint.arm.linux.org.uk> <20130704083307.GH10414@pengutronix.de> <51D53634.5040405@gmail.com> <20130704085313.GY516@pengutronix.de> <51D53C0B.6060106@gmail.com> <20130704092305.GI10414@pengutronix.de> <51D54301.8080902@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <51D54301.8080902-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: Sebastian Hesselbarth Cc: 'Jean-Francois Moine' , 'Daniel Drake' , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, Inki Dae , Russell King List-Id: devicetree@vger.kernel.org On Thu, Jul 04, 2013 at 11:40:17AM +0200, Sebastian Hesselbarth wrote: > On 07/04/13 11:23, Sascha Hauer wrote: > > > >With this you can describe the whole graph of devices you have in the > >devicetree. The examples in this file have a path from a camera sensor > >via a MIPI converter to a capture interface. > > > >The difference to a supernode is that this approach describes the data > >flow in the devicetree so that we can iterate over it to find links > >between source and sink rather than relying on a list of subdevices to > >be completed. > > Agree. But that is not that different from linux,video-external-encoder > property I made up, except that the name is different. > > And, I still see no way with that source/sink linking _alone_ how to > tell that either lcd0 and lcd1 act as a _single_ video card or lcd0 and > lcd1 are used in a _two_ video card setup. > > There is no single device node on Dove that would sufficiently act as > the top node for a working video card on all boards. And there is no > framebuffer node to link each of the lcd0/1 nodes to. > > That is what the super-node is for, form a virtual device called > video card to act as a container for all those SoC devices that are > not sufficient for a working video setup on their own. > > If lcd0 needs that hdmi-transmitter you link it to the lcd0 node - > not the super-node. If lcd0 needs some pll clock you link it to the > lcd0 node - again not the super-node. > > The super-node(s) just connects all SoC devices that shall be part of > your board-specific video card(s) - for Dove that is any combination of > lcd0, lcd0, dcon and video memory allocation. So with the supernode approach you would have one/two supernodes and with a v4l2 approach you would have either one graph containing lcd0 and lcd1 or to graphs (without a connection in between). Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |