Head-based output configuration API a.k.a clone mode infrastructure

From: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

Hi all,

all of the clone mode infrastructure has landed. There is just this one
patch remaining that actually allows one to use it through weston.ini.

Mind, this may be hard to test, because most contemporary PC graphics
devices might not support shared-CRTC clone mode at all. So if you try
this and face a frozen or black screen, it's likely that your hardware
just doesn't support this. An indication of no support is an error in
Weston log saying "atomic: couldn't commit new state" or "set mode
failed". Unfortunately, Weston does not recover from modeset failures
yet, but you should be able to quit gracefully with the usual
Ctrl+Alt+Backspace. You can still see in the Weston log how Weston tried
to configure clone mode.

I have used an i.MX6 based system to test.

This is also available in a GitLab(!) branch here along with the other
patch (force-on output) depending on this one:
https://gitlab.freedesktop.org/pq/weston/commits/clonemode-v10


The old Phabricator task (obsolete):
https://phabricator.freedesktop.org/T7727
The GitLab issue:
https://gitlab.freedesktop.org/wayland/weston/issues/22


Thanks,
pq

Pekka Paalanen (1):
  weston: support clone mode on DRM-frontend

 compositor/main.c  | 492 ++++++++++++++++++++++++++++++++++++++++++++++++++---
 man/weston-drm.man |  12 ++
 2 files changed, 484 insertions(+), 20 deletions(-)