media: imx: csi: Implement get_fwnode_pad op

The CSI does not have a 1:1 relationship between fwnode port numbers and
pad indexes. In fact the CSI fwnode device is itself a port which is the
sink, containing only a single fwnode endpoint. Implement media_entity
operation get_fwnode_pad to first verify the given endpoint is the CSI's
sink endpoint, and if so return the CSI sink pad index.
Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/imx/imx-media-csi.c

@@ -1832,9 +1832,32 @@ static void csi_unregistered(struct v4l2_subdev *sd)
 		ipu_csi_put(priv->csi);
 }
 
+/*
+ * The CSI has only one fwnode endpoint, at the sink pad. Verify the
+ * endpoint belongs to us, and return CSI_SINK_PAD.
+ */
+static int csi_get_fwnode_pad(struct media_entity *entity,
+			      struct fwnode_endpoint *endpoint)
+{
+	struct v4l2_subdev *sd = media_entity_to_v4l2_subdev(entity);
+	struct csi_priv *priv = v4l2_get_subdevdata(sd);
+	struct fwnode_handle *csi_port = dev_fwnode(priv->dev);
+	struct fwnode_handle *csi_ep;
+	int ret;
+
+	csi_ep = fwnode_get_next_child_node(csi_port, NULL);
+
+	ret = endpoint->local_fwnode == csi_ep ? CSI_SINK_PAD : -ENXIO;
+
+	fwnode_handle_put(csi_ep);
+
+	return ret;
+}
+
 static const struct media_entity_operations csi_entity_ops = {
 	.link_setup = csi_link_setup,
 	.link_validate = v4l2_subdev_link_validate,
+	.get_fwnode_pad = csi_get_fwnode_pad,
 };
 
 static const struct v4l2_subdev_core_ops csi_core_ops = {