Re: [PATCH net-next] net: dsa: fix preparation of a port STP update

[Andrew Lunn <andrew@lunn.ch>]

On Tue, Sep 29, 2015 at 12:38:36PM -0400, Vivien Didelot wrote:
> Because of the default 0 value of ret in dsa_slave_port_attr_set, a
> driver may return -EOPNOTSUPP from the commit phase of a STP state,
> which triggers a WARN() from switchdev.
> 
> This happened on a 6185 switch which does not support hardware bridging.
> 
> Reported-by: Andrew Lunn <andrew@lunn.ch>
> Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>

Acked-by: Andrew Lunn <andrew@lunn.ch>
Fixes: 3563606258cf ("switchdev: convert STP update to switchdev attr set")

David:
  This should be included in the next -rc.

Thanks
	Andrew

> ---
>  net/dsa/slave.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 0ae427c..02a3af8 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -453,12 +453,17 @@ static int dsa_slave_port_attr_set(struct net_device *dev,
>  				   struct switchdev_attr *attr,
>  				   struct switchdev_trans *trans)
>  {
> -	int ret = 0;
> +	struct dsa_slave_priv *p = netdev_priv(dev);
> +	struct dsa_switch *ds = p->parent;
> +	int ret;
>  
>  	switch (attr->id) {
>  	case SWITCHDEV_ATTR_PORT_STP_STATE:
> -		if (switchdev_trans_ph_commit(trans))
> -			ret = dsa_slave_stp_update(dev, attr->u.stp_state);
> +		if (switchdev_trans_ph_prepare(trans))
> +			ret = ds->drv->port_stp_update ? 0 : -EOPNOTSUPP;
> +		else
> +			ret = ds->drv->port_stp_update(ds, p->port,
> +						       attr->u.stp_state);
>  		break;
>  	default:
>  		ret = -EOPNOTSUPP;
> -- 
> 2.6.0
>