Best practice device tree design for display subsystems/DRM

[Sascha Hauer]

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.

Sascha

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