From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Hesselbarth Subject: Re: Best practice device tree design for display subsystems/DRM Date: Thu, 04 Jul 2013 11:44:41 +0200 Message-ID: <51D54409.6020608@gmail.com> References: <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> <20130704091131.GR13924@flint.arm.linux.org.uk> <20130704093047.GJ10414@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130704093047.GJ10414-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 , Russell King List-Id: devicetree@vger.kernel.org On 07/04/13 11:30, Sascha Hauer wrote: > On Thu, Jul 04, 2013 at 10:11:31AM +0100, Russell King wrote: >> 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. > > Indeed, then you will see nothing on your display, but I rather make > this setup a special case than the rather usual case that we do not > have compiled in all drivers for all devices referenced in the > supernode. The super-node links SoC internal devices that do not necessarily match with the subsystem driver. You have one single DRM driver exploiting several device nodes for a single video card. But you need one device node to hook the driver to. Sebastian