Re: [PATCH v8 net-next 11/12] net: dsa: mv88e6xxx: add blackhole ATU entries

[Vladimir Oltean]

On Tue, Oct 18, 2022 at 06:56:18PM +0200, Hans J. Schultz wrote:
> Blackhole FDB entries can now be added, deleted or replaced in the
> driver ATU.

Why is this necessary, why is it useful?

> 
> Signed-off-by: Hans J. Schultz <netdev@xxxxxxxxxxxxxxxxxxxx>
> ---
>  static int mv88e6xxx_port_fdb_add(struct dsa_switch *ds, int port,
>  				  const unsigned char *addr, u16 vid,
>  				  u16 fdb_flags, struct dsa_db db)
> @@ -2742,9 +2794,10 @@ static int mv88e6xxx_port_fdb_add(struct dsa_switch *ds, int port,
>  	struct mv88e6xxx_chip *chip = ds->priv;
>  	int err;
>  
> -	/* Ignore entries with flags set */
> -	if (fdb_flags)
> +	if (fdb_flags & DSA_FDB_FLAG_LOCKED)
>  		return 0;

I don't understand this. If no driver looks at DSA_FDB_FLAG_LOCKED
(not even mv88e6xxx, up until the end of the series), then why was it
propagated all the way in the first place?

> +	if (fdb_flags & DSA_FDB_FLAG_BLACKHOLE)
> +		return mv88e6xxx_blackhole_fdb_add(ds, addr, vid);
>  
>  	if (mv88e6xxx_port_is_locked(chip, port))
>  		mv88e6xxx_atu_locked_entry_find_purge(ds, port, addr, vid);
> @@ -2765,9 +2818,10 @@ static int mv88e6xxx_port_fdb_del(struct dsa_switch *ds, int port,
>  	bool locked_found = false;
>  	int err = 0;
>  
> -	/* Ignore entries with flags set */
> -	if (fdb_flags)
> +	if (fdb_flags & DSA_FDB_FLAG_LOCKED)
>  		return 0;
> +	if (fdb_flags & DSA_FDB_FLAG_BLACKHOLE)
> +		return mv88e6xxx_blackhole_fdb_del(ds, addr, vid);
>  
>  	if (mv88e6xxx_port_is_locked(chip, port))
>  		locked_found = mv88e6xxx_atu_locked_entry_find_purge(ds, port, addr, vid);
> -- 
> 2.34.1
>