drm: check for supported chipset before booting fbdev off the hw

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/nouveau_drm.c

@@ -325,7 +325,16 @@ static int nouveau_drm_probe(struct pci_dev *pdev,
 	    !vga_switcheroo_handler_flags())
 		return -EPROBE_DEFER;
 
-	/* remove conflicting drivers (vesafb, efifb etc) */
+	/* We need to check that the chipset is supported before booting
+	 * fbdev off the hardware, as there's no way to put it back.
+	 */
+	ret = nvkm_device_pci_new(pdev, NULL, "error", true, false, 0, &device);
+	if (ret)
+		return ret;
+
+	nvkm_device_del(&device);
+
+	/* Remove conflicting drivers (vesafb, efifb etc). */
 	aper = alloc_apertures(3);
 	if (!aper)
 		return -ENOMEM;