The title already implies the question, so what is blocking the execution from the sample program in this repo https://github.com/dvdhrm/docs/tree/master/drm-howto
It's a simple program showing KMS in action, so I downloaded it, compiled it and gave it a run. This was the output:
michael@lord:~/Downloads/docs/drm-howto$ sudo ./modeset
[sudo] password for michael:
using card '/dev/dri/card0'
mode for connector 59 is 1920x1080
ignoring unused connector 68
ignoring unused connector 71
ignoring unused connector 75
cannot set CRTC for connector 59 (13): Permission denied
exiting
Also note that I have a running X11 session on my machine.
It seems X is already using the device /dev/dri/card0 and blocks it for all other programs.
Here is my video card:
michael@lord:~/Downloads/docs/drm-howto$ lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 620 (rev 07)
I have also added i915.modeset=1 into /etc/initramfs-tools/modules and rebuilt it with sudo update-initramfs -u so it loads the driver from inside my kernel and not from the xorg side.
There is also the possibility that my driver doesn't support KMS but lspci has shown that I only have an internal intel graphics card installed. So I sticked with the xorg core display driver package which is installed by default from xserver-xorg-core.
None of these changes have taken affect. The only way I can execute those examples is by killing the xorg session and let it run in tty.
Any ideas?