netdev - Re: [PATCH net-next 15/15] net: mscc: ocelot: don't hardcode the number of the CPU port

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Date:   Sun, 10 Nov 2019 17:50:31 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     jakub.kicinski@...ronome.com, davem@...emloft.net,
        alexandre.belloni@...tlin.com, f.fainelli@...il.com,
        vivien.didelot@...il.com, joergen.andreasen@...rochip.com,
        allan.nielsen@...rochip.com, horatiu.vultur@...rochip.com,
        claudiu.manoil@....com, netdev@...r.kernel.org,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH net-next 15/15] net: mscc: ocelot: don't hardcode the
 number of the CPU port

On Sat, Nov 09, 2019 at 03:03:01PM +0200, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> VSC7514 is a 10-port switch with 2 extra "CPU ports" (targets in the
> queuing subsystem for terminating traffic locally).

So maybe that answers my last question.
 
> There are 2 issues with hardcoding the CPU port as #10:
> - It is not clear which snippets of the code are configuring something
>   for one of the CPU ports, and which snippets are just doing something
>   related to the number of physical ports.
> - Actually any physical port can act as a CPU port connected to an
>   external CPU (in addition to the local CPU). This is called NPI mode
>   (Node Processor Interface) and is the way that the 6-port VSC9959
>   (Felix) switch is integrated inside NXP LS1028A (the "local management
>   CPU" functionality is not used there).

So i'm having trouble reading this and spotting the difference between
the DSA concept of a CPU port and the two extra "CPU ports". Maybe
using the concept of virtual ports would help?

Are the physical ports number 0-9, and so port #10 is the first extra
"CPU port", aka a virtual port? And so that would not work for DSA,
where you need a physical port.

      Andrew