netdev - Representing cpu-port of a switch

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Date:   Mon, 30 Apr 2018 00:13:50 +0530
From:   "sk.syed2" <sk.syed2@...il.com>
To:     netdev@...r.kernel.org, jayaram@...inx.com, syeds@...inx.com
Subject: Representing cpu-port of a switch

Hi,
   Sorry if this has been discussed elsewhere. The relevant discussion
is here: https://www.spinics.net/lists/netdev/msg407313.html.
  But I have few questions in addition to those answered above. We
have simple 3-port switch, with two ports(connected via phys to
external(front panel)) and one cpu port connected to the cpu via dmas.
Our switch doesn't do any tagging protocol. It simply forwards a frame
to cpu based on fdb entry. Any frame can only be received/transmitted
only by this internal port.
Without tagging, we cant really use DSA, and hide the cpu/dsa port. So
if we expose this cpu port as a interface with fixed-phy
infrastructure does it create any problems? DSA documentation says one
cannot open a socket on cpu/dsa port and send/receive traffic. Is it
fairly common to use internal/cpu port as a network interface- i.e,
creating a socket and send/receive traffic?
One problem is how to report back when network errors(like if both
front panel ports are disconnected, the expectation is to bring this
cpu port down?).
We also need to offload all the switch configuration to switch-dev. So
the question is using switch-dev without DSA and representing a cpu
port as a normal network interface would be ok?

thanks
-syed