Fixed virtual box driver (drm_v5.4.144_6), sort of

Hi everyone,

Since I wanted to know how all things are working out between FreeBSD, DRM and Linux, I skimmed through the source and tested a lot with FBSD13 running in Virtual Box 6.x on FBSD13 host. Now I fixed the Makefiles and found the issue for the kernel panic which happens directly after loading the vbox DRM driver.
Within X11 everything looks now okay, multiple monitors as well as different resolutions work, but in the console there is still a bug making it unusable:
You can’t see any output, the console is frozen. If you force the repaint of the virtual machine window (moving other windows around or open the „about dialog“ of Virtual Box), the output is drawn. So console works, but the framebuffer output seems to have issues.
Do you have an idea where I could look to fix this issue? Is there any more documentation on how DRM works?
Also, how should I provide the fix? Diff here in the list, or PR in Github?

Best,
 Alexander