Alright. After a lot of work, I managed to get Mesa to compile from GIT,
together with the libdrm from latest GIT. However, I'm barely able to test
anything with it, as any game I open crashes.

I tried with 3 projects, and they all crash the moment any 3D is to be
rendered. There was however a very simple game that would run, although it uses
very small textures so there's barely anything to test. If you know a simple
application that can use a lot of vram and simulate the transfer, please point
it out.