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Documentation: networking: dsa: add paragraph for the MRP offload 

Add a short summary of the methods that a driver writer must implement
for getting an MRP instance to work on top of a DSA switch.

Cc: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vladimir Oltean 2021-03-16 13:24:16 +02:00 committed by David S. Miller
parent a9985444f2
commit f8f3c20af1
1 changed files with 30 additions and 0 deletions
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30
Documentation/networking/dsa/dsa.rst
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@ -757,6 +757,36 @@ 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.
IEC 62439-2 (MRP)
-----------------
The Media Redundancy Protocol is a topology management protocol optimized for
fast fault recovery time for ring networks, which has some components
implemented as a function of the bridge driver. MRP uses management PDUs
(Test, Topology, LinkDown/Up, Option) sent at a multicast destination MAC
address range of 01:15:4e:00:00:0x and with an EtherType of 0x88e3.
Depending on the node's role in the ring (MRM: Media Redundancy Manager,
MRC: Media Redundancy Client, MRA: Media Redundancy Automanager), certain MRP
PDUs might need to be terminated locally and others might need to be forwarded.
An MRM might also benefit from offloading to hardware the creation and
transmission of certain MRP PDUs (Test).
Normally an MRP instance can be created on top of any network interface,
however in the case of a device with an offloaded data path such as DSA, it is
necessary for the hardware, even if it is not MRP-aware, to be able to extract
the MRP PDUs from the fabric before the driver can proceed with the software
implementation. DSA today has no driver which is MRP-aware, therefore it only
listens for the bare minimum switchdev objects required for the software assist
to work properly. The operations are detailed below.
- ``port_mrp_add`` and ``port_mrp_del``: notifies driver when an MRP instance
with a certain ring ID, priority, primary port and secondary port is
created/deleted.
- ``port_mrp_add_ring_role`` and ``port_mrp_del_ring_role``: function invoked
when an MRP instance changes ring roles between MRM or MRC. This affects
which MRP PDUs should be trapped to software and which should be autonomously
forwarded.
TODO
====