netdev - Re: [net-next PATCH 1/5] net: dsa: tag_rtl4

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Message-ID: <20200604005407.GA977471@lunn.ch>
Date:   Thu, 4 Jun 2020 02:54:07 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev <netdev@...r.kernel.org>, DENG Qingfang <dqfext@...il.com>
Subject: Re: [net-next PATCH 1/5] net: dsa: tag_rtl4_a: Implement Realtek 4
 byte A tag

> > Where is spanning tree performed? In the switch, or by the
> > host?
> 
> In the switch I think.
> There is a register in the ASIC to set the spanning tree status
> to disabled, blocking, learning or forwarding.

Hi Linus

Spanning tree needs two parts. You need to be able to change the ports
between disabled, blocking, learning, forwarding. And you need to be
able to send/receive frames.

If spanning tree is performed in the ASIC, i don't see why there would
be registers to control the port status. It would do it all itself,
and not export these controls.

So i would not give up on spanning tree as a way to reverse engineer
this.

    Andrew