[media] omap3isp: Avoid a BUG_ON() in media_entity_create_link()

If an uninitialised v4l2_subdev struct was passed to
media_entity_create_link(), one of the BUG_ON()'s in the function will be
hit since media_entity.num_pads will be zero. Avoid this by checking whether
the num_pads field is non-zero for the interface.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/platform/omap3isp/isp.c

@@ -1946,6 +1946,19 @@ static int isp_register_entities(struct isp_device *isp)
 			goto done;
 		}
 
+		/*
+		 * Not all interfaces are available on all revisions
+		 * of the ISP. The sub-devices of those interfaces
+		 * aren't initialised in such a case. Check this by
+		 * ensuring the num_pads is non-zero.
+		 */
+		if (!input->num_pads) {
+			dev_err(isp->dev, "%s: invalid input %u\n",
+				entity->name, subdevs->interface);
+			ret = -EINVAL;
+			goto done;
+		}
+
 		for (i = 0; i < sensor->entity.num_pads; i++) {
 			if (sensor->entity.pads[i].flags & MEDIA_PAD_FL_SOURCE)
 				break;