I forgot to say this: for those who have this bug, simply add this line in a service which is launched before X' start (e.g. in /etc/init/lightdm.conf, just after the line with 'script'):
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch
I forgot to say this: for those who have this bug, simply add this line in a service which is launched before X' start (e.g. in /etc/init/ lightdm. conf, just after the line with 'script'):
echo OFF > /sys/kernel/ debug/vgaswitch eroo/switch