users of drm-legacy-kmod or drm drivers from base

[ This is cross-posted across several mailing lists for maximum 
visibility.  Please respect reply-to and keep replies to x11_at_FreeBSD.org 
. Thank you! ]

In order to improve support for the new lkpi based graphics drivers 
(drm-kmod) and to improve the graphics stack we have switched mesa to 
prefer DRI3 over DRI2.  This was done in r528071.  For those using 
drm-kmod, this should improve performance somewhat, and more importantly 
alleviate the use of the FIXDRM option (now removed) in xorg-server.

However, for those of you using graphics/drm-legacy-kmod or the drm 
drivers in base, this change can cause issues.  If you are experiencing 
problems when running OpenGL applications, you can force the use of the 
DRI2 backend.

To force mesa to use DRI2, set the environment variable 
LIBGL_DRI3_DISABLE to 1 before starting any OpenGL application.  The 
easiest way to accomplish this is by adding it to either your shell 
startup file or ~/.xinitrc.

As an example, for users of [t]csh, put
setenv LIBGL_DRI3_DISABLE 1
in ~/.cshrc.

For users of bourne type shells (sh, bash, ksh, zsh, ...) instead put
export LIBGL_DRI3_DISABLE=1
in ~/.profile

If you are using these legacy drivers, I'm also very interested in 
hearing what issues you are facing that prevents you from using the new 
lkpi based drivers.

Regards
-- 
Niclas Zeising
FreeBSD Graphics Team