netdev - Re: [PATCH v2 net-next 8/8] net: dsa: mv88e6xxx: Offload bridge broadcast flooding flag

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Message-ID: <20210318143505.5lu3ebozbkrayygp@skbuf>
Date:   Thu, 18 Mar 2021 16:35:05 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Tobias Waldekranz <tobias@...dekranz.com>
Cc:     davem@...emloft.net, kuba@...nel.org, andrew@...n.ch,
        vivien.didelot@...il.com, f.fainelli@...il.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 8/8] net: dsa: mv88e6xxx: Offload bridge
 broadcast flooding flag

On Thu, Mar 18, 2021 at 03:15:50PM +0100, Tobias Waldekranz wrote:
> These switches have two modes of classifying broadcast:
> 
> 1. Broadcast is multicast.
> 2. Broadcast is its own unique thing that is always flooded
>    everywhere.
> 
> This driver uses the first option, making sure to load the broadcast
> address into all active databases. Because of this, we can support
> per-port broadcast flooding by (1) making sure to only set the subset
> of ports that have it enabled whenever joining a new bridge or VLAN,
> and (2) by updating all active databases whenever the setting is
> changed on a port.
> 
> Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
> ---
>  drivers/net/dsa/mv88e6xxx/chip.c | 73 +++++++++++++++++++++++++++++++-
>  1 file changed, 72 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
> index 7976fb699086..3baa4dadb0dd 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.c
> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> @@ -1982,6 +1982,21 @@ static int mv88e6xxx_broadcast_setup(struct mv88e6xxx_chip *chip, u16 vid)
>  	int err;
>  
>  	for (port = 0; port < mv88e6xxx_num_ports(chip); port++) {
> +		struct dsa_port *dp = dsa_to_port(chip->ds, port);
> +		struct net_device *brport;
> +
> +		if (dsa_is_unused_port(chip->ds, port))
> +			continue;
> +
> +		brport = dsa_port_to_bridge_port(dp);
> +
> +		if (dp->bridge_dev &&
> +		    !br_port_flag_is_set(brport, BR_BCAST_FLOOD))

I think I would have liked to see a dsa_port_to_bridge_port helper that
actually returns NULL when dp->bridge_dev is NULL.

This would make your piece of code look as follows:

		brport = dsa_port_to_bridge_port(dp);
		if (brport && !br_port_flag_is_set(brport, BR_BCAST_FLOOD)
			continue;

> +			/* Skip bridged user ports where broadcast
> +			 * flooding is disabled.
> +			 */
> +			continue;
> +
>  		err = mv88e6xxx_port_add_broadcast(chip, port, vid);
>  		if (err)
>  			return err;