[Intel-gfx] [PATCH] Reintegrate legacy UMS.

[Chris Wilson]

You probably heard the screams of terror at the prospect of adding 50k
lines of broken code. The result of that shock was that it did produce a
viable alternative: use a shadow fb and avoid dynamic reallocation and
associated incoherency issues.

The benefits of this approach is that we get KMS (hotplug, resizable
framebuffers, rotation, reliable suspend and resume), overlays (video)
reasonable performance, and continued development. You lose GL
acceleration. (But using GEM it would suffer the same incoherency problems
that plagued X, and unless you were also using an old DRI1 compatible
version of Mesa, legacy/ums could do no better.) You also lose EXA
acceleration, but that turns out to be a good thing in the general case,
but synthetic benchmarks will show decreased performance.

The branch is available for testing from

http://cgit.freedesktop.org/~ickle/xf86-video-intel/log/?h=shadow

To enable the use of the shadow, you will have to add

Section "Device"
  Option "Shadow" "True"
EndSection

to your xorg.conf.

-- 
Chris Wilson, Intel Open Source Technology Centre