[PATCH] [RFC] drm/i915/dp: add support for load detect Apple DP->VGA dongles

[Daniel Vetter]

On Fri, Jun 06, 2014 at 12:57:46PM +0300, Jani Nikula wrote:
> On Fri, 06 Jun 2014, Dave Airlie <airlied at gmail.com> wrote:
> > From: Dave Airlie <airlied at redhat.com>
> >
> > The DP1.2 spec has some bits for forced load sensing on VGA dongles,
> > however the apple dongle I have doesn't do DP 1.2 yet, so I dug into
> > its vendor specific area and found a register that seems to correspond
> > to load detected on the outputs.
> >
> > The main reason I need this was at LCA this year the slide capture system
> > failed to provide EDID, but I realised OSX worked. Really need to add support
> > to nouveau, but hey i915 is a start.
> >
> > The dongle also appears to use short IRQs to denote a plug/unplug event,
> > though something seems to be failing in reading back the dpcd values from it.
> > (also this is based on my MST work just because.)
> 
> Good timing for making use of the OUI! See
> 
> http://mid.gmane.org/1401920981-3137-1-git-send-email-clinton.a.taylor@intel.com
> 
> > Signed-off-by: Dave Airlie <airlied at redhat.com>

Just a high-level bikeshed: Now that we have this nice dp helper library
shouldn't we add a dp_detect function there which fills out a bunch of
sink state in the core dp struct and also implements tricks like this?
Maybe as the plain dp version of the relevant dp mst handler?

Definitely not much point in copy&pasting this for radeon, noveau, tegra
and all the others.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch