netdev - Re: [PATCH net-next 2/3] net: dsa: Allow default tag protocol to be overridden from DT

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Date:   Mon, 29 Mar 2021 00:53:09 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Tobias Waldekranz <tobias@...dekranz.com>, davem@...emloft.net,
        kuba@...nel.org, vivien.didelot@...il.com, f.fainelli@...il.com,
        netdev@...r.kernel.org, robh+dt@...nel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] net: dsa: Allow default tag protocol to be
 overridden from DT

On Sun, Mar 28, 2021 at 05:52:43PM +0200, Andrew Lunn wrote:
> > +static int dsa_switch_setup_tag_protocol(struct dsa_switch *ds)
> > +{
> > +	const struct dsa_device_ops *tag_ops = ds->dst->tag_ops;
> > +	struct dsa_switch_tree *dst = ds->dst;
> > +	int port, err;
> > +
> > +	if (tag_ops->proto == dst->default_proto)
> > +		return 0;
> > +
> > +	if (!ds->ops->change_tag_protocol) {
> > +		dev_err(ds->dev, "Tag protocol cannot be modified\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	for (port = 0; port < ds->num_ports; port++) {
> > +		if (!(dsa_is_dsa_port(ds, port) || dsa_is_cpu_port(ds, port)))
> > +			continue;
> 
> dsa_is_dsa_port() is interesting. Do we care about the tagging
> protocol on DSA ports? We never see that traffic?

I believe this comes from me (see dsa_switch_tag_proto_match). I did not
take into consideration at that time the fact that Marvell switches can
translate between DSA and EDSA. So I assumed that every switch in the
tree needs a notification about the tagging protocol, not just the
top-most one.