linux-kernel - Re: [net-next v4 4/5] net: mtip: The L2 switch driver for imx287

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Message-ID: <cab89673-6126-43ff-b7eb-1f311fa4498b@lunn.ch>
Date: Wed, 9 Apr 2025 23:26:08 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Lukasz Majewski <lukma@...x.de>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, davem@...emloft.net,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Richard Cochran <richardcochran@...il.com>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	Stefan Wahren <wahrenst@....net>
Subject: Re: [net-next v4 4/5] net: mtip: The L2 switch driver for imx287

> +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;
> +
> +	/* 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);

This is not an error condition as such. The switch cannot do it, so
-EOPNOTSUPP is correct, but the Linux software bridge can, and it
will. So there is no need to use NL_SET_ERR_MSG_MOD().


> +		}
> +
> +		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);
> +
> +	dev_dbg(&ndev->dev,
> +		"%s: ndev: %s br: %s fep: 0x%x members: 0x%x offload: %d\n",
> +		__func__, ndev->name,  br_ndev->name, (unsigned int)fep,
> +		fep->br_members, fep->br_offload);
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static void mtip_netdevice_port_unlink(struct net_device *ndev)
> +{
> +	struct mtip_ndev_priv *priv = netdev_priv(ndev);
> +	struct switch_enet_private *fep = priv->fep;
> +
> +	dev_dbg(&ndev->dev, "%s: ndev: %s members: 0x%x\n", __func__,
> +		ndev->name, fep->br_members);
> +
> +	fep->br_members &= ~BIT(priv->portnum - 1);
> +	priv->master_dev = NULL;
> +
> +	if (!fep->br_members) {
> +		fep->br_offload = 0;
> +		mtip_switch_en_port_separation(fep);
> +		mtip_clear_atable(fep);
> +	}

This does not look quite correct. So you disable port separation once
both ports are a member of the same bridge. So you should enable port
separation as soon as one leaves. So if fep->br_members has 0 or 1
bits set, you need to enable port separation.

	Andrew