netdev - Re: [PATCH net-next v2 3/7] net: dsa: Register devlink ports before calling DSA driver setup()

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Message-ID: <20200927004514.GC3889809@lunn.ch>
Date:   Sun, 27 Sep 2020 02:45:14 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Jiri Pirko <jiri@...dia.com>, Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net-next v2 3/7] net: dsa: Register devlink ports before
 calling DSA driver setup()

> > +static int dsa_port_devlink_setup(struct dsa_port *dp)
> >  {
> >  	struct devlink_port *dlp = &dp->devlink_port;
> > +	struct dsa_switch_tree *dst = dp->ds->dst;
> > +	struct devlink_port_attrs attrs = {};
> > +	struct devlink *dl = dp->ds->devlink;
> > +	const unsigned char *id;
> > +	unsigned char len;
> > +	int err;
> > +
> > +	id = (const unsigned char *)&dst->index;
> > +	len = sizeof(dst->index);
> > +
> > +	attrs.phys.port_number = dp->index;
> > +	memcpy(attrs.switch_id.id, id, len);
> > +	attrs.switch_id.id_len = len;
> > +
> > +	if (dp->setup)
> > +		return 0;
> >  
> 
> I wonder what this is protecting against? I ran on a multi-switch tree
> without these 2 lines and I didn't get anything like multiple
> registration or things like that. What is the call path that would call
> dsa_port_devlink_setup twice?

I made a duplicate copy of dsa_port_setup() and trimmed out what was
not needed to give the new dsa_port_setup() and
dsa_port_devlink_setup(). I did not trim enough...

> 
> > +	switch (dp->type) {
> > +	case DSA_PORT_TYPE_UNUSED:
> > +		memset(dlp, 0, sizeof(*dlp));
> > +		attrs.flavour = DEVLINK_PORT_FLAVOUR_UNUSED;
> 
> > +		devlink_port_attrs_set(dlp, &attrs);
> > +		err = devlink_port_register(dl, dlp, dp->index);
> 
> These 2 lines are common everywhere. Could you move them out of the
> switch-case statement?

Yes, that makes sense. Too much blind copy/paste without actually
reviewing the code afterwards.

	  Andrew