Re: [net-next,v20,7/7] net: mtip: Extend the L2 switch driver for imx287 with bridge operations

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net: mtip: Extend the L2 switch driver for imx287 with bridge operations

This patch adds bridge operations support to the MTIP L2 switch driver,
enabling hardware offloading for packet switching when a bridge is
created on the switch interfaces.

[ ... ]

+static int mtip_ndev_port_link(struct net_device *ndev,
+			       struct net_device *br_ndev,
+			       struct netlink_ext_ack *extack)
+{
+	struct mtip_ndev_priv *priv = netdev_priv(ndev), *other_priv;
+	struct switch_enet_private *fep = priv->fep;
+	struct net_device *other_ndev;
+	int err;
+
+	/* Check if one port of MTIP switch is already bridged */
+	if (fep->br_members && !fep->br_offload) {
+		/* Get the second bridge ndev */
+		other_ndev = fep->ndev[fep->br_members - 1];
+		other_priv = netdev_priv(other_ndev);
+		if (other_priv->master_dev != br_ndev) {
+			NL_SET_ERR_MSG_MOD(extack,
+					   "L2 offloading only possible for the same bridge!");
+			return notifier_from_errno(-EOPNOTSUPP);

                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Should this return -EOPNOTSUPP instead of notifier_from_errno(-EOPNOTSUPP)?
The caller mtip_netdevice_event() already wraps the return value with
notifier_from_errno(ret), so double-wrapping corrupts the return value.

Looking at similar drivers like cpsw_new.c (cpsw_netdevice_port_link),
the pattern is to return raw errno values here and let the event handler
do the conversion.

+		}
+
+		fep->br_offload = 1;
+		mtip_switch_dis_port_separation(fep);
+		mtip_clear_atable(fep);
+	}
+
+	if (!priv->master_dev)
+		priv->master_dev = br_ndev;
+
+	fep->br_members |= BIT(priv->portnum - 1);
+
+	err = switchdev_bridge_port_offload(ndev, ndev, NULL, NULL, NULL,
+					    false, extack);
+	if (err) {
+		dev_err(&ndev->dev, "can't offload bridge port %s [err: %d]\n",
+			ndev->name, err);
+		return err;
+	}

If switchdev_bridge_port_offload() fails, the state changes made earlier
in the function (br_offload, br_members, master_dev, and the hardware
configuration via mtip_switch_dis_port_separation and mtip_clear_atable)
are not rolled back.

Looking at cpsw_new.c for reference, it modifies br_members after the
switchdev call succeeds, avoiding the need for rollback. Could the state
updates here be reordered to happen after switchdev_bridge_port_offload()
returns successfully?

[ ... ]

+static int mtip_netdevice_event(struct notifier_block *unused,
+				unsigned long event, void *ptr)
+{

[ ... ]

+	return notifier_from_errno(ret);
+}

[ ... ]