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

[Or Gerlitz]

Sean Hefty wrote:
>> 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.

I don't think there's a need for module params here, as Sean stated, the 
impl. provide default values and the user can override them.

The smartness here should be on the user side, so if they don't like the 
idea of default values, we can remove them, instead of providing a way 
to set the default values...

>> 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.

Again, as this API is targeted for "plain and native IB" apps that is 
applications that does not want to use the IPoIB association from 
network to rdma devices (which is used by the CMA to know the pkey etc), 
if the application want to look in the /sys files of the root/child 
interface to learn the pkey etc params, let them do it.

Or.