Re: [PATCH v4 net-next 12/15] net: dsa: track the number of switches in a tree

[Florian Fainelli <f.fainelli@gmail.com>]

On 7/18/2021 2:44 PM, Vladimir Oltean wrote:
> In preparation of supporting data plane forwarding on behalf of a
> software bridge, some drivers might need to view bridges as virtual
> switches behind the CPU port in a cross-chip topology.
> 
> Give them some help and let them know how many physical switches there
> are in the tree, so that they can count the virtual switches starting
> from that number on.
> 
> Note that the first dsa_switch_ops method where this information is
> reliably available is .setup(). This is because of how DSA works:
> in a tree with 3 switches, each calling dsa_register_switch(), the first
> 2 will advance until dsa_tree_setup() -> dsa_tree_setup_routing_table()
> and exit with error code 0 because the topology is not complete. Since
> probing is parallel at this point, one switch does not know about the
> existence of the other. Then the third switch comes, and for it,
> dsa_tree_setup_routing_table() returns complete = true. This switch goes
> ahead and calls dsa_tree_setup_switches() for everybody else, calling
> their .setup() methods too. This acts as the synchronization point.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian