Quoting ?HonzaHavlicek:

• The nv_demos are small programs used for RE of nvidia commands and registers. They are not drivers and they do not use DRI/Gallium3D. They manually set up objects and write some commands to FIFO. The developer write some code to nv_demo and hopes to achieve some result (triangle, repated texture, scissors..). She will achieve the expected result (mostly) after a few (painfull) hours (days). General principle is to look at the MMIO and renouveau dumps and try to repeat what nvidia blob did. Sometimes it is a single bit, sometimes the whole infrastructure.
  • nv04_demo http://nouveau.cvs.sourceforge.net/nouveau/nv04_demo/
  • nv10_demo http://nouveau.cvs.sourceforge.net/nouveau/nv10_demo/
  • nv20_demo http://cgit.freedesktop.org/~pq/nv20_demo/
  • nv30_demo http://cgit.freedesktop.org/~jkolb/nv30_demo/
  • another nv30_demo http://cgit.freedesktop.org/~pmandin/nv30_demo/
  • nv40_demo http://nouveau.cvs.sourceforge.net/nouveau/nv40_demo/

Instructions (nv10_demo in this example)

•   cvs -d:pserver:anonymous@nouveau.cvs.sourceforge.net:/cvsroot/nouveau login
  cvs -z3 -d:pserver:anonymous@nouveau.cvs.sourceforge.net:/cvsroot/nouveau co -P nv10_demo

  Then enter nv10_demo and just run make.

The binary requires access to the drm module, run it using root: sudo ./nouveau_demo.