linux-kernel - Re: [PATCH net-next v3 08/12] net: dsa: rzn1-a5psw: add FDB support

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Date:   Thu, 5 May 2022 15:44:31 +0200
From:   Clément Léger <clement.leger@...tlin.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Herve Codina <herve.codina@...tlin.com>,
        Miquèl Raynal <miquel.raynal@...tlin.com>,
        Milan Stevanovic <milan.stevanovic@...com>,
        Jimmy Lalande <jimmy.lalande@...com>,
        Pascal Eberhard <pascal.eberhard@...com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v3 08/12] net: dsa: rzn1-a5psw: add FDB support

Le Wed, 4 May 2022 19:24:57 +0300,
Vladimir Oltean <olteanv@...il.com> a écrit :

> On Wed, May 04, 2022 at 11:29:56AM +0200, Clément Léger wrote:
> > +static int a5psw_port_fdb_del(struct dsa_switch *ds, int port,
> > +			      const unsigned char *addr, u16 vid,
> > +			      struct dsa_db db)
> > +{
> > +	struct a5psw *a5psw = ds->priv;
> > +	union lk_data lk_data = {0};
> > +	bool clear = false;
> > +	int ret = 0;
> > +	u16 entry;
> > +	u32 reg;
> > +
> > +	ether_addr_copy(lk_data.entry.mac, addr);
> > +
> > +	spin_lock(&a5psw->lk_lock);
> > +
> > +	ret = a5psw_lk_execute_lookup(a5psw, &lk_data, &entry);
> > +	if (ret) {
> > +		dev_err(a5psw->dev, "Failed to lookup mac address\n");
> > +		goto lk_unlock;
> > +	}
> > +
> > +	lk_data.hi = a5psw_reg_readl(a5psw, A5PSW_LK_DATA_HI);
> > +	if (!lk_data.entry.valid) {
> > +		dev_err(a5psw->dev, "Tried to remove non-existing entry\n");
> > +		ret = -ENOENT;
> > +		goto lk_unlock;  
> 
> These error messages can happen under quite normal use with your hardware.
> For example:
> 
> ip link add br0 type bridge && ip link set br0 master br0
> bridge fdb add dev swp0 00:01:02:03:04:05 vid 1 master static
> bridge fdb add dev swp0 00:01:02:03:04:05 vid 2 master static
> bridge fdb del dev swp0 00:01:02:03:04:05 vid 2 master static
> bridge fdb del dev swp0 00:01:02:03:04:05 vid 1 master static
> 
> Because the driver ignores the VID, then as soon as the VID 2 FDB entry
> is removed, the VID 1 FDB entry doesn't exist anymore, either.

Argh did not thought about that but indeed, that will for sure trigger
the error.

> 
> The above is a bit artificial. More practically, the bridge installs
> local FDB entries (MAC address of bridge device, MAC addresses of ports)
> once in the VLAN-unaware database (VID 0), and once per VLAN installed
> on br0.

Ok, seems clear.

> 
> When the MAC address of br0 is different from that of the ports, and it
> is changed by the user, you'll get these errors too, since those changes
> translate into a deletion of the old local FDB entries (installed as FDB
> entries towards the CPU port). Do you want the users to see them and
> think something is wrong?  I mean, something _is_ wrong (the hardware),
> but you have to work with that somehow.

Indeed, I'll simply remove these error message. Should I still return
an error value however ? Seems like I should not to avoid triggering
any error that might confuse the user.

-- 
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com