NAME

       ibv_alloc_mw, ibv_dealloc_mw - allocate or deallocate a memory window (MW)

SYNOPSIS

       #include <infiniband/verbs.h>

       struct ibv_mw *ibv_alloc_mw(struct ibv_pd *pd,
                                   enum ibv_mw_type type);

       int ibv_dealloc_mw(struct ibv_mw *mw);

DESCRIPTION

       ibv_alloc_mw() allocates a memory window (MW) associated with the protection domain pd.  The MW's type (1
       or 2A/2B) is type.

       The  MW is created not bound. For it to be useful, the MW must be bound, through either ibv_bind_mw (type
       1) or a special WR (type 2).  Once bound, the memory window allows RDMA (remote) access to  a  subset  of
       the  MR  to  which  it  was  bound,  until  invalidated by: ibv_bind_mw verb with zero length for type 1,
       IBV_WR_LOCAL_INV/IBV_WR_SEND_WITH_INV WR opcode for type 2, deallocation.

       ibv_dealloc_mw() Unbinds in case was previously bound and deallocates the MW mw.

RETURN VALUE

       ibv_alloc_mw() returns a pointer to the allocated MW, or NULL if  the  request  fails.   The  remote  key
       (R_Key)  field  rkey  is used by remote processes to perform Atomic and RDMA operations. This key will be
       changed during bind operations. The remote  process  places  this  rkey  as  the  rkey  field  of  struct
       ibv_send_wr passed to the ibv_post_send function.

       ibv_dealloc_mw()  returns  0  on  success,  or the value of errno on failure (which indicates the failure
       reason).

NOTES

       ibv_dereg_mr() fails if any memory window is still bound to this MR.

SEE ALSO

       ibv_alloc_pd(3), ibv_post_send(3), ibv_bind_mw(3), ibv_reg_mr(3),

AUTHORS

       Majd Dibbiny <majd@mellanox.com>

       Yishai Hadas <yishaih@mellanox.com>

libibverbs                                         2016-02-02                                    IBV_ALLOC_MW(3)