[ofa-general] Re: [PATCHv4 RFC] Scalable Reliable Connection: API and documentation

[Roland Dreier]

 > +++ b/SRC.txt
 > @@ -0,0 +1,138 @@
 > +Here's some documentation on Scalable Reliable Connections.

I think this would be more useful in the man page for
ibv_open_src_domain() (which needs to be written ;).

You know, reading over the patch, it strikes me that "src" is a very
confusing acronym, since it really looks like an abbreviation for
"source."  I don't know what would be better off the top of my head
but ideas would be appreciated.

 > --- a/src/libibverbs.map
 > +++ b/src/libibverbs.map
 > @@ -24,6 +24,7 @@ IBVERBS_1.0 {
 >  		ibv_get_cq_event;
 >  		ibv_ack_cq_events;
 >  		ibv_create_srq;
 > +		ibv_create_src_srq;
 >  		ibv_modify_srq;
 >  		ibv_query_srq;
 >  		ibv_destroy_srq;
 > @@ -35,6 +36,8 @@ IBVERBS_1.0 {
 >  		ibv_destroy_ah;
 >  		ibv_attach_mcast;
 >  		ibv_detach_mcast;
 > +		ibv_open_src_domain;
 > +		ibv_close_src_domain;
 >  		ibv_cmd_get_context;
 >  		ibv_cmd_query_device;
 >  		ibv_cmd_query_port;

These new symbols definitely don't belong in the IBVERBS_1.0 ABI.  In
fact since this all changes structure layout I think we need to create
an IBVERBS_1.2 ABI and create compat-1_1.c to deal with it.

Also, if we're going to change the signature of the create_srq method:

 >  	struct ibv_srq *	(*create_srq)(struct ibv_pd *pd,
 > +					      struct ibv_src_domain *src_domain,
 > +					      struct ibv_cq *src_cq,
 >  					      struct ibv_srq_init_attr *srq_init_attr);

then I think we need something like

#define IBV_CREATE_SRQ_METHOD_HAS_SRC_PARAMS

so that driver libraries can still work with both old and new
libibverbs.  I'm not sure the gain of avoiding a new entry point is
worth forcing every driver library (even the ones that don't do SRC)
to change -- it might be better to mimic the consumer API and just
have a new create_srq_srq method.  That way driver libraries that
don't do SRC would stay source compatible (I think).

 - R.