drm_vblank_init
r = drm_vblank_init(adev->ddev, adev->mode_info.num_crtc);
if (drm_vblank_init(adev->ddev, adev->dm.display_indexes_num)) {
EXPORT_SYMBOL(drm_vblank_init);
ret = drm_vblank_init(&dev_priv->drm,
int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs);
r = drm_vblank_init(rdev->ddev, rdev->num_crtc);