[ewg] RE: ofed 1.2 multicast patch documentation

[Sean Hefty]

>The ib_sa/rdmacm multicast code in ofed 1.2 comes in the form of one big
>  undocumented patch (merged_sean_rdma_dev_ofed_1_2.patch), is the below
>fine as a change log comment?

Yes - this should work for the change log comment.

- Sean

>Or.
>
>>     Author: Sean Hefty <sean.hefty at intel.com>
>>     RDMA/cma: Add multicast communication support
>>
>>     Extend rdma_cm to support multicast communication.  Multicast support
>>     is added to the existing RDMA_PS_UDP port space, as well as a new
>>     RDMA_PS_IPOIB port space.  The latter port space allows joining the
>>     multicast groups used by IPoIB, which enables offloading IPoIB traffic
>>     to a separate QP.  The port space determines the signature used in the
>>     MGID when joining the group.  The newly added RDMA_PS_IPOIB also
>>     allows for unicast operations, similar to RDMA_PS_UDP.
>>
>>     Supporting the RDMA_PS_IPOIB requires changing how UD QPs are
>initialized,
>>     since we can no longer assume that the qkey is constant.  This requires
>>     saving the Q_Key to use when attaching to a device, so that it is
>>     available when creating the QP.  The Q_Key information is exported to
>>     the user through the existing rdma_init_qp_attr() interface.
>>
>>     Multicast support is also exported to userspace through the rdma_ucm.
>>
>>     Signed-off-by: Roland Dreier <rolandd at cisco.com>
>>
>>
>>     Author: Sean Hefty <sean.hefty at intel.com>
>>     IB/sa: Track multicast join/leave requests
>>
>>     The IB SA tracks multicast join/leave requests on a per port basis and
>>     does not do any reference counting: if two users of the same port join
>>     the same group, and one leaves that group, then the SA will remove the
>>     port from the group even though there is one user who wants to stay a
>>     member left.  Therefore, in order to support multiple users of the
>>     same multicast group from the same port, we need to perform reference
>>     counting locally.
>>
>>     To do this, add an multicast submodule to ib_sa to perform reference
>>     counting of multicast join/leave operations.  Modify ib_ipoib (the
>>     only in-kernel user of multicast) to use the new interface.
>>
>>     Signed-off-by: Roland Dreier <rolandd at cisco.com>
>>