[RFC PATCH net-next 02/20] net: dsa: assign a bridge number even without TX forwarding offload

@@ -3090,8 +3090,8 @@ static int mv88e6xxx_setup(struct dsa_switch *ds)
 	 * time.
 	 */
 	if (mv88e6xxx_has_pvt(chip))
-		ds->num_fwd_offloading_bridges = MV88E6XXX_MAX_PVT_SWITCHES -
-						 ds->dst->last_switch - 1;
+		ds->max_num_bridges = MV88E6XXX_MAX_PVT_SWITCHES -
+				      ds->dst->last_switch - 1;
 
 	mv88e6xxx_reg_lock(chip);
 

@@ -3055,7 +3055,7 @@ static int sja1105_setup(struct dsa_switch *ds)
 	ds->vlan_filtering_is_global = true;
 	ds->untag_bridge_pvid = true;
 	/* tag_8021q has 3 bits for the VBID, and the value 0 is reserved */
-	ds->num_fwd_offloading_bridges = 7;
+	ds->max_num_bridges = 7;
 
 	/* Advertise the 8 egress queues */
 	ds->num_tx_queues = SJA1105_NUM_TC;

@@ -407,12 +407,12 @@ struct dsa_switch {
 	 */
 	unsigned int		num_lag_ids;
 
-	/* Drivers that support bridge forwarding offload should set this to
-	 * the maximum number of bridges spanning the same switch tree (or all
-	 * trees, in the case of cross-tree bridging support) that can be
-	 * offloaded.
+	/* Drivers that support bridge forwarding offload or FDB isolation
+	 * should set this to the maximum number of bridges spanning the same
+	 * switch tree (or all trees, in the case of cross-tree bridging
+	 * support) that can be offloaded.
 	 */
-	unsigned int		num_fwd_offloading_bridges;
+	unsigned int		max_num_bridges;
 
 	size_t num_ports;
 };

@@ -271,19 +271,15 @@ static void dsa_port_switchdev_unsync_attrs(struct dsa_port *dp)
 }
 
 static void dsa_port_bridge_tx_fwd_unoffload(struct dsa_port *dp,
-					     struct net_device *bridge_dev)
+					     struct net_device *bridge_dev,
+					     int bridge_num)
 {
-	int bridge_num = dp->bridge_num;
 	struct dsa_switch *ds = dp->ds;
 
 	/* No bridge TX forwarding offload => do nothing */
-	if (!ds->ops->port_bridge_tx_fwd_unoffload || dp->bridge_num == -1)
+	if (!ds->ops->port_bridge_tx_fwd_unoffload || bridge_num == -1)
 		return;
 
-	dp->bridge_num = -1;
-
-	dsa_bridge_num_put(bridge_dev, bridge_num);
-
 	/* Notify the chips only once the offload has been deactivated, so
 	 * that they can update their configuration accordingly.
 	 */

@@ -292,32 +288,65 @@ static void dsa_port_bridge_tx_fwd_unoffload(struct dsa_port *dp,
 }
 
 static bool dsa_port_bridge_tx_fwd_offload(struct dsa_port *dp,
-					   struct net_device *bridge_dev)
+					   struct net_device *bridge_dev,
+					   int bridge_num)
 {
 	struct dsa_switch *ds = dp->ds;
-	int bridge_num, err;
-
-	if (!ds->ops->port_bridge_tx_fwd_offload)
-		return false;
+	int err;
 
-	bridge_num = dsa_bridge_num_get(bridge_dev,
-					ds->num_fwd_offloading_bridges);
-	if (bridge_num < 0)
+	/* FDB isolation is required for TX forwarding offload */
+	if (!ds->ops->port_bridge_tx_fwd_offload || bridge_num == -1)
 		return false;
 
-	dp->bridge_num = bridge_num;
-
 	/* Notify the driver */
 	err = ds->ops->port_bridge_tx_fwd_offload(ds, dp->index, bridge_dev,
 						  bridge_num);
-	if (err) {
-		dsa_port_bridge_tx_fwd_unoffload(dp, bridge_dev);
+	if (err)
 		return false;
-	}
 
 	return true;
 }
 
+static int dsa_port_assign_bridge(struct dsa_port *dp,
+				  struct net_device *br,
+				  struct netlink_ext_ack *extack)
+{
+	struct dsa_switch *ds = dp->ds;
+	int bridge_num;
+
+	dp->bridge_dev = br;
+
+	if (!ds->max_num_bridges)
+		return 0;
+
+	bridge_num = dsa_bridge_num_get(br, ds->max_num_bridges);
+
+	if (bridge_num < 0) {
+		NL_SET_ERR_MSG_MOD(extack,
+				   "Range of offloadable bridges exceeded");
+		return -EOPNOTSUPP;
+	}
+
+	dp->bridge_num = bridge_num;
+
+	return 0;
+}
+
+static void dsa_port_unassign_bridge(struct dsa_port *dp,
+				     const struct net_device *br)
+{
+	struct dsa_switch *ds = dp->ds;
+
+	dp->bridge_dev = NULL;
+
+	if (ds->max_num_bridges) {
+		int bridge_num = dp->bridge_num;
+
+		dp->bridge_num = -1;
+		dsa_bridge_num_put(br, bridge_num);
+	}
+}
+
 int dsa_port_bridge_join(struct dsa_port *dp, struct net_device *br,
 			 struct netlink_ext_ack *extack)
 {

@@ -335,7 +364,9 @@ int dsa_port_bridge_join(struct dsa_port *dp, struct net_device *br,
 	/* Here the interface is already bridged. Reflect the current
 	 * configuration so that drivers can program their chips accordingly.
 	 */
-	dp->bridge_dev = br;
+	err = dsa_port_assign_bridge(dp, br, extack);
+	if (err)
+		return err;
 
 	brport_dev = dsa_port_to_bridge_port(dp);
 

@@ -343,7 +374,8 @@ int dsa_port_bridge_join(struct dsa_port *dp, struct net_device *br,
 	if (err)
 		goto out_rollback;
 
-	tx_fwd_offload = dsa_port_bridge_tx_fwd_offload(dp, br);
+	tx_fwd_offload = dsa_port_bridge_tx_fwd_offload(dp, br,
+							dp->bridge_num);
 
 	err = switchdev_bridge_port_offload(brport_dev, dev, dp,
 					    &dsa_slave_switchdev_notifier,

@@ -386,14 +418,15 @@ void dsa_port_bridge_leave(struct dsa_port *dp, struct net_device *br)
 		.port = dp->index,
 		.br = br,
 	};
+	int bridge_num = dp->bridge_num;
 	int err;
 
 	/* Here the port is already unbridged. Reflect the current configuration
 	 * so that drivers can program their chips accordingly.
 	 */
-	dp->bridge_dev = NULL;
+	dsa_port_unassign_bridge(dp, br);
 
-	dsa_port_bridge_tx_fwd_unoffload(dp, br);
+	dsa_port_bridge_tx_fwd_unoffload(dp, br, bridge_num);
 
 	err = dsa_broadcast(DSA_NOTIFIER_BRIDGE_LEAVE, &info);
 	if (err)