Re: [net-next,v22,7/7] net: mtip: Extend the L2 switch driver for imx287 with bridge operations

[Jakub Kicinski <kuba@kernel.org>]

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

This commit adds bridge offloading support to the MTIP L2 switch driver,
allowing the switch to offload packet switching when a bridge is
created on its interfaces.

> diff --git a/drivers/net/ethernet/freescale/mtipsw/mtipl2sw_br.c b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw_br.c
> --- /dev/null
> +++ b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw_br.c
> @@ -0,0 +1,132 @@

[ ... ]

> +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 -EOPNOTSUPP;
> +		}
> +
> +		fep->br_offload = 1;
> +		mtip_switch_dis_port_separation(fep);
> +		mtip_clear_atable(fep);
> +	}
> +
> +	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;
> +	}

When switchdev_bridge_port_offload() fails after the second port joins the
same bridge, should the error path also revert br_offload and port
separation state?

In mtip_ndev_port_link() when the second port joins, the code sets
fep->br_offload = 1 and calls mtip_switch_dis_port_separation() before
attempting switchdev_bridge_port_offload(). If that call fails, the error
returns without reverting these changes.

This could leave the hardware with port separation disabled and br_offload
set to 1, even though only one port is actually bridged.

This concern was raised by Jakub Kicinski:
https://lore.kernel.org/netdev/20260131015440.972531-1-kuba@kernel.org/