[PATCH net-next v2] net: dsa: mt7530: add support for changing DSA master

[Vladimir Oltean]

On Sat, Feb 11, 2023 at 07:41:01PM +0100, Richard van Schagen wrote:
> Add support for changing the master of a port on the MT7530 DSA subdriver.
> 
> 
> Tested-by: Arınç ÜNAL <arinc.unal at arinc9.com>
> Signed-off-by: Richard van Schagen <richard at routerhints.com>
> Signed-off-by: Arınç ÜNAL <arinc.unal at arinc9.com>
> ---

Currently with this driver, the only way for a frame to reach the CPU is
via flooding. The DSA framework can do better: it can configure the driver
to only accept certain whitelisted MAC addresses, which reduces unwanted
traffic to the CPU. But it needs driver level support for some prerequisites,
namely FDB isolation, se see dsa_switch_supports_uc_filtering() and
dsa_switch_supports_mc_filtering().

If somebody decides to add support for RX filtering later to the mt7530 driver,
he might not have access to a setup with multiple CPU ports. So this
might become a blocking issue for him.

Would it make more sense to unlock RX filtering for the mt7530 driver
now, and to make the FDB entries added on the CPU ports work when
multiple CPU ports exist, too? Now seems like the most logical moment to
do that, not later.