[openib-general] RFC userspace CMA

[Caitlin Bestler]

> -----Original Message-----
> From: Sean Hefty [mailto:mshefty at ichips.intel.com] 
> Sent: Wednesday, October 26, 2005 10:40 AM
> To: Caitlin Bestler
> Cc: Tom Tucker; openib
> Subject: Re: [openib-general] RFC userspace CMA
> 
> Caitlin Bestler wrote:
> > How much logic is really in the RDMA CM?
> > 
> > If it is sufficiently small, which is what my expectation 
> is, would it 
> > make sense to simply make the IB CM and IW CM conform to the same 
> > polymorphic interface? (Making the "RDMA CM" little more than a 
> > re-directing inline function).
> > 
> > But if there is any substantial portion of common logic 
> then the above 
> > structure definitely makes sense.
> 
> The kernel CMA is about 660 lines of code.  It performs QP 
> transitions for the user, abstracts device remove/addition, 
> plus controls the mapping from IP to IB. 
>   (The mapping function makes use of external modules, such 
> as ib_addr and
> sa_query.)
> 
> In some places, the implementation of the API of the RDMA CM 
> does little more than redirecting to the IW/IB CM, coupled 
> with synchronization for device removal.  However, it also 
> handles the IB CM callbacks to provide simpler connection 
> notification.
> 

So it sounds like the justification for the RDMA CM being
a distinct module is to centralize handling of device addition
and removal. Beyond that you are incorporating IB-specific
but device-independent logic. As a goal, the iWARP side
should be migrating there as well.