linux-kernel - Re: [PATCH] net: dsa: mv88e6xxx: avoid error message on remove from VLAN 0

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Date:   Fri, 31 May 2019 11:00:17 -0400
From:   Vivien Didelot <vivien.didelot@...il.com>
To:     Nikita Yushchenko <nikita.yoush@...entembedded.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Marek Behún <marek.behun@....cz>,
        Russell King <rmk+kernel@...linux.org.uk>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH] net: dsa: mv88e6xxx: avoid error message on remove from
 VLAN 0

Hi Nikita,

On Fri, 31 May 2019 17:46:29 +0300, Nikita Yushchenko <nikita.yoush@...entembedded.com> wrote:
> 
> 
> 31.05.2019 17:37, Andrew Lunn wrote:
> >> I'm not sure that I like the semantic of it, because the driver can actually
> >> support VID 0 per-se, only the kernel does not use VLAN 0. Thus I would avoid
> >> calling the port_vlan_del() ops for VID 0, directly into the upper DSA layer.
> >>
> >> Florian, Andrew, wouldn't the following patch be more adequate?
> >>
> >>     diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> >>     index 1e2ae9d59b88..80f228258a92 100644
> >>     --- a/net/dsa/slave.c
> >>     +++ b/net/dsa/slave.c
> >>     @@ -1063,6 +1063,10 @@ static int dsa_slave_vlan_rx_kill_vid(struct net_device *dev, __be16 proto,
> >>             struct bridge_vlan_info info;
> >>             int ret;
> >>      
> >>     +       /* VID 0 has a special meaning and is never programmed in hardware */
> >>     +       if (!vid)
> >>     +               return 0;
> >>     +
> >>             /* Check for a possible bridge VLAN entry now since there is no
> >>              * need to emulate the switchdev prepare + commit phase.
> >>              */
> >  
> Kernel currently does, but it is caught in
> mv88e6xxx_port_check_hw_vlan() and returns -ENOTSUPP from there.

But VID 0 has a special meaning for the kernel, it means the port's private
database (when it is isolated, non-bridged), it is not meant to be programmed
in the switch. That's why I would've put that knowledge into the DSA layer,
which job is to translate the kernel operations to the (dumb) DSA drivers.

I hope I'm seeing things correctly here.


Thanks,
Vivien