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

[Sean Hefty]

>>Would we be okay with extending the IOCTL interface to allow multicast joins, 
>>notice registration, and event reporting?  Or would it be acceptable to change 
>>the ib_umad read/write interface to add a command?
> 
> 
> What do you have in mind here ?

I was thinking of one of two possibilities here.  Currently there are IOCTL 
calls to register/unregister with the MAD layer.  Additional IOCTL calls could 
be added to join/leave multicast groups and register/unregister for SA events. 
Multicast and SA events would need to be reported through another IOCTL of some 
sort.

The alternative basically rewrites the ib_umad interface to allow read and write 
to carry some sort of command, rather than mapping them directly to sending and 
receiving a MAD.  This is how most of the RDMA kernel to user interfaces are 
written.  For example, let read return an event type (MAD received, multicast 
event, etc.), along with the event data (the MAD, etc.).

>>>As an alternative, a new kernel userspace SA module could be created to
>>>explicitly interface with the kernel ib_sa.
> 
> IMO, this is the best way to go.

This was my original approach a couple of months back, but wasn't accepted as 
mer gable upstream because it increased the size of the user to kernel 
interface.  If we can agree that this approach is usable, we can discuss more 
specific implementation details.

- Sean