From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King Subject: Re: Best practice device tree design for display subsystems/DRM Date: Thu, 4 Jul 2013 10:11:31 +0100 Message-ID: <20130704091131.GR13924@flint.arm.linux.org.uk> References: <20130702191923.GD13924@flint.arm.linux.org.uk> <51D330AC.5060903@gmail.com> <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> <20130704084052.GP13924@flint.arm.linux.org.uk> <20130704085817.GZ516@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20130704085817.GZ516-bIcnvbaLZ9MEGnE8C9+IrQ@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: Sascha Hauer Cc: 'Jean-Francois Moine' , 'Daniel Drake' , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, Inki Dae , 'Sebastian Hesselbarth' List-Id: devicetree@vger.kernel.org On Thu, Jul 04, 2013 at 10:58:17AM +0200, Sascha Hauer wrote: > On Thu, Jul 04, 2013 at 09:40:52AM +0100, Russell King wrote: > > Wrong. Please read the example with the diagrams I gave. Consider > > what happens if you have two display devices connected to a single > > output, one which fixes the allowable mode and one which _can_ > > reformat the selected mode. > > What you describe here is a forced clone mode. This could be described > in the devicetree so that a driver wouldn't start before all connected > displays (links) are present, but this should be limited to the affected > path, not to the whole componentized device. Okay, to throw a recent argument back at you: so what in this scenario if you have a driver for the fixed-mode device but not the other device? It's exactly the same problem which you were describing to Sebastian just a moment ago with drivers missing from the supernode approach - you can't start if one of those "forced clone" drivers is missing. -- Russell King