I think that if a PCI bus is a root bus, attached to a host bridge not a

PCI->PCI bridge, then bus->self is allowed to be NULL. Certainly that's
the case on my Pegasos, and it makes the MGA DRM driver oops...
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/char/drm/mga_drv.c

@@ -161,7 +161,7 @@ static int mga_driver_device_is_agp(drm_device_t * dev)
 	 * device.
 	 */
 
-	if ((pdev->device == 0x0525)
+	if ((pdev->device == 0x0525) && pdev->bus->self
 	    && (pdev->bus->self->vendor == 0x3388)
 	    && (pdev->bus->self->device == 0x0021)) {
 		return 0;