From: Vladimir Oltean <vladimir.olt...@nxp.com> Add a short summary of the methods that a driver writer must implement for offloading a link aggregation group, and what is still missing.
Cc: Tobias Waldekranz <tob...@waldekranz.com> Signed-off-by: Vladimir Oltean <vladimir.olt...@nxp.com> --- Documentation/networking/dsa/dsa.rst | 32 ++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/Documentation/networking/dsa/dsa.rst b/Documentation/networking/dsa/dsa.rst index 463b48714fe9..0a5b06cf4d45 100644 --- a/Documentation/networking/dsa/dsa.rst +++ b/Documentation/networking/dsa/dsa.rst @@ -698,6 +698,38 @@ Bridge VLAN filtering function that the driver has to call for each MAC address known to be behind the given port. A switchdev object is used to carry the VID and MDB info. +Link aggregation +---------------- + +Link aggregation is implemented in the Linux networking stack by the bonding +and team drivers, which are modeled as virtual, stackable network interfaces. +DSA is capable of offloading a link aggregation group (LAG) to hardware that +supports the feature, and supports bridging between physical ports and LAGs, +as well as between LAGs. A bonding/team interface which holds multiple physical +ports constitutes a logical port, although DSA has no explicit concept of a +physical port at the moment. Due to this, events where a LAG joins/leaves a +bridge are treated as if all individual physical ports that are members of that +LAG join/leave the bridge. Switchdev port attributes (VLAN filtering, STP +state, etc) on a LAG are treated similarly: DSA offloads the same switchdev +port attribute on all members of the LAG. Switchdev objects on a LAG (FDB, MDB) +are not yet supported, since the DSA driver API does not have the concept of a +logical port ID. + +- ``port_lag_join``: function invoked when a given switch port is added to a + LAG. The driver may return ``-EOPNOTSUPP``, and in this case, DSA will fall + back to a software implementation where all traffic from this port is sent to + the CPU. +- ``port_lag_leave``: function invoked when a given switch port leaves a LAG + and returns to operation as a standalone port. +- ``port_lag_change``: function invoked when the link state of any member of + the LAG changes, and the hashing function needs rebalancing only towards the + subset of physical LAG member ports that are up. + +Drivers that benefit from having an ID associated with each offloaded LAG +can optionally populate ``ds->num_lag_ids`` from the ``dsa_switch_ops::setup`` +method. The LAG ID associated with a bonding/team interface can then be +retrieved by a DSA switch driver using the ``dsa_lag_id`` function. + TODO ==== -- 2.25.1
