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Date: Tue, 2 Jun 2015 21:39:50 -0400 (EDT)
From: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: netdev <netdev@vger.kernel.org>, David <davem@davemloft.net>,
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        =?utf-8?Q?J=C3=A9rome?= Oufella 
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Subject: Re: [RFC 3/9] net: dsa: mv88e6xxx: add support for VTU ops
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Guenter,

On Jun 2, 2015, at 2:50 AM, Guenter Roeck linux@roeck-us.net wrote:
> On 06/01/2015 06:27 PM, Vivien Didelot wrote:
>> +    /* Bringing an interface up adds it to the VLAN 0. Ignore this. */
>> +    if (!vid)
>> +        return 0;
>> +
> 
> Me puzzled ;-). I brought this and the fid question up before.
> No idea if my e-mail got lost or what happened.
> 
> Can you explain why we don't need a configuration for vlan 0 ?

Sorry for late reply. Initially, when issuing "ip link set up dev swp0",
ndo_vlan_rx_add_vid was called to add the interface in the VLAN 0.

2 things happen here:

  * this is inconsistent with the "bridge vlan" output which doesn't seem to
    know about a VID 0;
  * VID 0 seems special for this switch: if an ingressing frame has VID 0, the
    tagged port will override the VID bits with the port default VID at egress.

Thanks,
-v