drm_vblank_count
last = drm_vblank_count(dev, pipe);
last != drm_vblank_count(dev, pipe),
seq = drm_vblank_count(dev, pipe);
vblank_passed(drm_vblank_count(dev, pipe),
vblank = drm_vblank_count(dev, pipe);
return drm_vblank_count(crtc->dev, drm_crtc_index(crtc));