netdev - Re: [PATCH net-next 4/6] net: dsa: mv88e6xxx: do not change STP state on port disabling

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Message-ID: <20190819122737.GB16144@t480s.localdomain>
Date:   Mon, 19 Aug 2019 12:27:37 -0400
From:   Vivien Didelot <vivien.didelot@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, marek.behun@....cz, davem@...emloft.net,
        f.fainelli@...il.com
Subject: Re: [PATCH net-next 4/6] net: dsa: mv88e6xxx: do not change STP state
 on port disabling

On Mon, 19 Aug 2019 18:10:18 +0200, Andrew Lunn <andrew@...n.ch> wrote:
> > On Mon, 19 Aug 2019 15:40:57 +0200, Andrew Lunn <andrew@...n.ch> wrote:
> > > On Sun, Aug 18, 2019 at 01:35:46PM -0400, Vivien Didelot wrote:
> > > > When disabling a port, that is not for the driver to decide what to
> > > > do with the STP state. This is already handled by the DSA layer.
> > > 
> > > Putting the port into STP disabled state is how you actually disable
> > > it, for the mv88e6xxx. So this is not really about STP, it is about
> > > powering off the port. Maybe a comment is needed, rather than removing
> > > the code?
> > 
> > This is not for the driver to decide, the stack already handles that.
> > Otherwise, calling dsa_port_disable on a bridged port would result in
> > mv88e6xxx forcing the STP state to Disabled while this is not expected.

[...]

> Are you saying the core already sets the STP to disabled, for ports
> which are unused? I did not spot that in your previous patch?

Just look at dsa_port_disable Andrew:


    void dsa_port_disable(struct dsa_port *dp)
    {
    	struct dsa_switch *ds = dp->ds;
    	int port = dp->index;
    
    	if (!dp->bridge_dev)
    		dsa_port_set_state_now(dp, BR_STATE_DISABLED);
    
    	if (ds->ops->port_disable)
    		ds->ops->port_disable(ds, port);
    }


The only thing worth arguing here is whether it makes sense to call
ds->ops->disable for a bridged port, or should we simply return right
away in this case. But this would be an independent patch anyway.


Thank you,

	Vivien