[openib-general] [PATCH] multicast: add support for MGID 0

[Sean Hefty]

>These are the hard coded values for pkey, qkey, and join state mentioned
>above. Should there be module parameters to override them ?

My thought was that a user could override any of the values before creating the
group.  I'm not sure module parameters are necessary, but I do see how they
might be useful.  I'll see what others think.

>Also, where do the other parameters (components) that are necessary to
>create a group come from ?

They default to 0.  I looked at the values returned for the ipoib broadcast
group that was running on my system, and coded the values to match that.

>Another option would be to obtain all of them from the appropriate
>(partition based) IPoIB broadcast group.

I agree, and this is what the RDMA CM does.  This was the future extension that
I mentioned, since there are still issues that would need to be worked out.
Including partition information in the query changes the API.  Also, ipoib
depends on the ib_multicast module, so ib_multicast cannot rely on ipoib being
loaded.  It may work better for a user to get the broadcast address that they
want, then query for that MGID, but I haven't looked at this enough to know what
makes the most sense yet.

- Sean