[elrepo] skylake, nvidia, bumblebee

[Nicolas Thierry-Mieg]

Hello,

as mentioned a few weeks ago I am trying to get C7 fully functional on a 
new Acer Aspire E5-575G-55DE laptop, which has an intel i5-6200U with 
integrated HD Graphics 520 as well as a nvidia GeForce GTX 950M.

Thanks to advice from this list I got the intel graphics to work with 
the standard EL7 kernel by adding i915.preliminary_hw_support=1 to the 
kernel options.

I then followed the instructions from http://elrepo.org/tiki/bumblebee 
to install the nvidia kmod and driver, as well as bumblebee. After 
rebooting I get a "Oh no! Something has gone wrong" screen.

I managed to fix this by
sudo mv /usr/lib64/xorg/modules/extensions/nvidia/ /usr/lib64/xorg/
and modifying XorgModulePath accordingly in bumblebee.conf .

Everything now works: I can now boot in X mode (using the intel gpu) and 
start applications using the nvidia gpu with optirun.

Comparing the Xorg.0.log files between initial (broken) install and 
after my fix, the main difference is (removing timestamps for readability):

BROKEN:
(II) LoadModule: "glx"
(II) Loading /usr/lib64/xorg/modules/extensions/nvidia/libglx.so
(EE) Failed to load /usr/lib64/xorg/modules/extensions/nvidia/libglx.so: 
libnvidia-tls.so.367.44: cannot open shared object file: No such file or 
directory
(II) UnloadModule: "glx"
(II) Unloading glx
(EE) Failed to load module "glx" (loader failed, 7)

FIXED:
(II) LoadModule: "glx"
(II) Loading /usr/lib64/xorg/modules/extensions/libglx.so
(II) Module glx: vendor="X.Org Foundation"
	compiled for 1.17.2, module version = 1.0.0
	ABI class: X.Org Server Extension, version 9.0
(==) AIGLX enabled


So it seems that when the nvidia libglx is in 
/usr/lib64/modules/extensions/nvidia/libglx.so , X tries to load that 
instead of the correct /usr/lib64/xorg/modules/extensions/libglx.so .

This is surprising because in both cases I have:
(==) ModulePath set to "/usr/lib64/xorg/modules"


The elrepo instructions worked for me on another laptop with 
intel+nvidia, so I don't understand. I had to fiddle with a bunch of 
things on this laptop, both for this nvidia problem and to try to get 
the wifi working, so it's possible I screwed up something. But I've 
double-checked everything I could think of without finding the culprit.
So, does anyone have any ideas why X is picking up the wrong libglx.so 
here? I'm willing to check any files and test things, I just don't know 
where to look or what to try now.

Thanks,
Nicolas