Xrandr issue with Thinkpad T420 and more than two displays

Hi all,

we have an issue with more advanced X configuration and multiple displays.
Up to two displays is fine, but more than two and it gets complicated. This is under RHEL 6.4 with X Server 1.13 and Nvidia Driver 310.32.

Configuration has been taken from: https://wiki.archlinux.org/index.php/Lenovo_ThinkPad_T420s#Example_X.org-Configuration_using_Intel_and_NVIDIA_together

Problem is that with this setup X is working, but XRANDR is disabled during X startup, and I’d like some hints how to enable/enforce it to be able to resize screens and so on.

Also OpenGL is disabled during X startup, as half of the display is driven by the Integrated Intel graphics. How can this be enabled for all screens? We can also use a different driver, nouveau or nv if that’s easier to handle.

nvidia-bug-report_sb.log.gz (22.2 MB)

If more information is required, just let me know ;)

RandR is not supported when the server’s Xinerama support is enabled:

OpenGL in this configuration only works on GPUs that are identical (or at least very similar) to the one driving screen 0. In your configuration, you can’t use OpenGL on the Intel screen:

See Chapter 13. Configuring GLX in Xinerama in the README for more information.

If you use a sufficiently new Linux kernel and X server, you can try using PRIME display offload instead of Xinerama. That way, all of the rendering will happen on the NVIDIA GPU and just the display will be offloaded to the Intel chip. See Chapter 33. Offloading Graphics Display with RandR 1.4 if you want to give that a shot.