Subject: Re: [patch net-next RFC 04/12] rtnl: expose physical switch id for particular device

From: John Fastabend <[email-masked]>
Date: Fri, 22 Aug 2014 12:08:39 -0700

On 08/21/2014 09:18 AM, Jiri Pirko wrote:
> The netdevice represents a port in a switch, it will expose
> IFLA_PHYS_SWITCH_ID value via rtnl. Two netdevices with the same value
> belong to one physical switch.
>
> Signed-off-by: Jiri Pirko <[email-masked]>

What is the relation between phys_port_id and phys_switch_id?

phys_port_id was intended to identify a set of ports that belong
to a single uplink port,

	eth0     eth1    eth2   eth3      (host facing)
           |       |       |      |
           |       |       |      |
       +---+-------+-------+------+---+
       |      embedded switch         |
       +------------------------------+
                      |
                     MAC                   (network)

In the NIC case there is a simply switch with a port to the
network which we currently don't represent with a netdev. Any
netdev where the phys_switch_id's are behind the same embedded
switch.

In the switch id case we are indicating the port is attached to
the same embedded switch as well.

          eth0 eth1 eth2 eth3
           |    |    |    |
      +----+----+----+----+----+
      |         switch         |
      +----+----+----+----+----+

but they do not share an uplink port? So in this case each ethx
has a unique phys_port_id but the same phys_switch_id?

In the first case both phys_port_id and phys_switch_id should
be equal for all interfaces correct?

Is that clear/useful at all? We need to document this somewhere
if/when the patches are submitted otherwise I doubt we will get it
consistently right across drivers. There could for example be
somewhat strange devices with virtual functions hanging off of the
switch.

Thanks,
John

-- 
John Fastabend         Intel Corporation