netdev - Re: [PATCH net 14/15] docs: net: dsa: delete misinformation about -EOPNOTSUPP for FDB/MDB/VLAN

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Date:   Sun, 17 Jul 2022 17:50:17 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH net 14/15] docs: net: dsa: delete misinformation about
 -EOPNOTSUPP for FDB/MDB/VLAN

On Sat, Jul 16, 2022 at 09:53:43PM +0300, Vladimir Oltean wrote:
> Returning -EOPNOTSUPP does *NOT* mean anything special.
> 
> port_vlan_add() is actually called from 2 code paths, one is
> vlan_vid_add() from 8021q module and the other is
> br_switchdev_port_vlan_add() from switchdev.
> 
> The bridge has a wrapper __vlan_vid_add() which first tries via
> switchdev, then if that returns -EOPNOTSUPP, tries again via the VLAN RX
> filters in the 8021q module. But DSA doesn't distinguish between one
> call path and the other when calling the driver's port_vlan_add(), so if
> the driver returns -EOPNOTSUPP to switchdev, it also returns -EOPNOTSUPP
> to the 8021q module. And the latter is a hard error.
> 
> port_fdb_add() is called from the deferred dsa_owq only, so obviously
> its return code isn't propagated anywhere, and cannot be interpreted in
> any way.
> 
> The return code from port_mdb_add() is propagated to the bridge, but
> again, this doesn't do anything special when -EOPNOTSUPP is returned,
> but rather, br_switchdev_mdb_notify() returns void.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew