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

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Date:	Fri, 22 Aug 2014 12:08:39 -0700
From:	John Fastabend <john.fastabend@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
CC:	netdev@...r.kernel.org, davem@...emloft.net, nhorman@...driver.com,
	andy@...yhouse.net, tgraf@...g.ch, dborkman@...hat.com,
	ogerlitz@...lanox.com, jesse@...ira.com, pshelar@...ira.com,
	azhou@...ira.com, ben@...adent.org.uk, stephen@...workplumber.org,
	jeffrey.t.kirsher@...el.com, vyasevic@...hat.com,
	xiyou.wangcong@...il.com, john.r.fastabend@...el.com,
	edumazet@...gle.com, jhs@...atatu.com, sfeldma@...ulusnetworks.com,
	f.fainelli@...il.com, roopa@...ulusnetworks.com,
	linville@...driver.com, dev@...nvswitch.org, jasowang@...hat.com,
	ebiederm@...ssion.com, nicolas.dichtel@...nd.com,
	ryazanov.s.a@...il.com, buytenh@...tstofly.org,
	aviadr@...lanox.com, nbd@...nwrt.org, alexei.starovoitov@...il.com,
	Neil.Jerram@...aswitch.com, ronye@...lanox.com
Subject: Re: [patch net-next RFC 04/12] rtnl: expose physical switch id for
 particular device

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 <jiri@...nulli.us>

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
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