ARM topic: Is DT on ARM the solution, or is there something better?

[Sascha Hauer]

On Thu, Oct 24, 2013 at 11:00:56AM +0200, Thierry Reding wrote:
> On Thu, Oct 24, 2013 at 09:28:11AM +0200, Sascha Hauer wrote:
> > On Wed, Oct 23, 2013 at 09:14:17PM -0400, Rob Clark wrote:
> > > On Mon, Oct 21, 2013 at 5:27 AM, Sascha Hauer <s.hauer at pengutronix.de> wrote:
> > > >> If a subsystem doesn't work well with DT, then the choices are either:
> > > >>
> > > >> (a) don't use DT with the subsystem
> > > >
> > > > The underlying problem has nothing to do with DT. Multi component
> > > > hardware does exist and won't vanish when we stop using DT.
> > > >
> > > >> (b) fix the subsystem
> > > >
> > > > I'd love to do that. Step one to this seems to be to increase the
> > > > awareness that there's something wrong with DRM.
> > > 
> > > 
> > > Note that I suspect your idea of "fixing drm" is going to break some
> > > userspace assumptions about the hw (ie. userspace isn't expecting
> > > crtcs/encoders/connectors to suddenly appear/disappear.  And the funny
> > > thing is, on all of this hw, that isn't going to happen anyways.
> > 
> > I was talking about all SoC DRM drivers implementing variants of the
> > same glue between drm and the multidevice nature of the components.
> > 
> > To make that sure: I never had the intention to implement hotplug for
> > drm. Also what the imx-drm driver does is not for hotplug, but only for
> > binding different components together.
> 
> I think we should be able to solve that problem generically. Essentially
> we need some sort of composite device that subdevices can register with.
> The composite device can keep track of what devices are needed (this
> works well by walking the device tree, looking for nodes that match by
> compatible and see if their status property is set to"okay") and once
> all of those have been registered do whatever the specific subsystem
> requires.

It would be great to have a generic approach to this since subsystems
like ASoC and v4l2 have the same problem.

Sascha

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