[openib-general] [RFC] userspace IB SA support

[Sean Hefty]

>1. Join a multicast group - needs to use the ib_sa multicast capability.

Adding this functionality to the existing ib_umad module would add an extra
dependency of ib_umad on the ib_sa module.  Multicast join / leave operations
could be done by adding additional IOCTLs, by embedding the request as a
send_mad call, or by modifying the ib_umad send interface.

As an alternative, a new kernel userspace SA module could be created to
explicitly interface with the kernel ib_sa.

>2. Receive notification of multicast errors.

Add to this, receive notification of the join as well.  This could be
accomplished by returning the relevant data (SA attribute only) through
libibumad recv_mad.  This would change the behavior of the user/kernel
interface, but I'm not sure how many applications would be affected by the
change.

>3. Leave a multicast group.
>4. Register to receive SA events - needs to use the ib_sa notice capability.
>5. Receive notification of events.
>6. Deregister from SA events.

SA event notification could be handled similarly to multicast...

- Sean