DRM_VBLANKTIME_RBSIZE
dev->_vblank_time = malloc(num_crtcs * DRM_VBLANKTIME_RBSIZE *
(dev)->_vblank_time[(crtc) * DRM_VBLANKTIME_RBSIZE + \
((count) % DRM_VBLANKTIME_RBSIZE)])
memset(&dev->_vblank_time[crtc * DRM_VBLANKTIME_RBSIZE], 0,
DRM_VBLANKTIME_RBSIZE * sizeof(struct timeval));