[ofa-general] fast path operation?

[Roland Dreier]

 > I got another question about your code for mthca HCA. In the 
 > "mthca_provider.c", the functions "mthca_create_cq(struct ib_device 
 > *ibdev, int entries, struct ib_ucontext *context, struct ib_udata *udata)" 
 > and "mthca_alloc_pd(struct ib_device *ibdev, struct ib_ucontext *context, 
 > struct ib_udata *udata)" all have a parameter "ib_ucontext*", while in the 
 > "Verbs.c", the calling functions "ib_create_cq" and "ib_alloc_pd" all pass 
 > "NULL" to this parameter, is the " ib_ucontext *" only needed for fast 
 > path operation, in which situation the user application can write directly 
 > to user space? If it's true, how to set up the fast path operation in the 
 > driver environment?

Yes, the struct ib_ucontext is used for objects that are created and
accessed in userspace.  The parameter will be non-NULL for commands
from drivers/infiniband/core/uverbs_cmd.c.

 - R.