linux-kernel - Re: [PATCH] net: dsa: tag_brcm: legacy: fix daisy-chained switches

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Message-ID: <00783066-a99c-4bab-ae60-514f4bce687b@lunn.ch>
Date:   Fri, 17 Mar 2023 17:32:01 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Álvaro Fernández Rojas <noltari@...il.com>
Cc:     f.fainelli@...il.com, jonas.gorski@...il.com, olteanv@...il.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: dsa: tag_brcm: legacy: fix daisy-chained switches

On Fri, Mar 17, 2023 at 01:08:15PM +0100, Álvaro Fernández Rojas wrote:
> When BCM63xx internal switches are connected to switches with a 4-byte
> Broadcom tag, it does not identify the packet as VLAN tagged, so it adds one
> based on its PVID (which is likely 0).
> Right now, the packet is received by the BCM63xx internal switch and the 6-byte
> tag is properly processed. The next step would to decode the corresponding
> 4-byte tag. However, the internal switch adds an invalid VLAN tag after the
> 6-byte tag and the 4-byte tag handling fails.
> In order to fix this we need to remove the invalid VLAN tag after the 6-byte
> tag before passing it to the 4-byte tag decoding.

Is there an errata for this invalid VLAN tag? Or is the driver simply
missing some configuration for it to produce a valid VLAN tag?

The description does not convince me you are fixing the correct
problem.

	Andrew