On Xorg log file I have the folowing traces :
drmOpenDevice : node name is /dev/dri/card0
[drm] failed to load kernel module "vivante"
There is no directory "/dev/dri". According to Ubuntu Software Center the installed vivante driver is "gpu-viv-ubt0 12.11.01.oneiric.MX6DQ.post GA.RC3"
What I have to install to allow running GL2 applications.