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CentOS 7.0 - man page for ibv_poll_cq (centos section 3)

IBV_POLL_CQ(3)			  Libibverbs Programmer's Manual		   IBV_POLL_CQ(3)

NAME
       ibv_poll_cq - poll a completion queue (CQ)

SYNOPSIS
       #include <infiniband/verbs.h>

       int ibv_poll_cq(struct ibv_cq *cq, int num_entries,
		       struct ibv_wc *wc);

DESCRIPTION
       ibv_poll_cq()  polls  the CQ cq for work completions and returns the first num_entries (or
       all available completions if the CQ contains fewer than this number) in the array wc.  The
       argument  wc  is  a  pointer  to  an  array  of	ibv_wc	structs,  as  defined in <infini-
       band/verbs.h>.

       struct ibv_wc {
	       uint64_t 	       wr_id;	       /* ID of the completed Work Request (WR) */
	       enum ibv_wc_status      status;	       /* Status of the operation */
	       enum ibv_wc_opcode      opcode;	       /* Operation type specified in the completed WR */
	       uint32_t 	       vendor_err;     /* Vendor error syndrome */
	       uint32_t 	       byte_len;       /* Number of bytes transferred */
	       uint32_t 	       imm_data;       /* Immediate data (in network byte order) */
	       uint32_t 	       qp_num;	       /* Local QP number of completed WR */
	       uint32_t 	       src_qp;	       /* Source QP number (remote QP number) of completed WR (valid only for UD QPs) */
	       int		       wc_flags;       /* Flags of the completed WR */
	       uint16_t 	       pkey_index;     /* P_Key index (valid only for GSI QPs) */
	       uint16_t 	       slid;	       /* Source LID */
	       uint8_t		       sl;	       /* Service Level */
	       uint8_t		       dlid_path_bits; /* DLID path bits (not applicable for multicast messages) */
       };

       The attribute wc_flags describes the properties of the work completion.	It is either 0 or
       the bitwise OR of one or more of the following flags:

       IBV_WC_GRH  GRH is present (valid only for UD QPs)

       IBV_WC_WITH_IMM	Immediate data value is valid

       Not all wc attributes are always valid. If the completion status is other than IBV_WC_SUC-
       CESS, only the following attributes are valid: wr_id, status, qp_num, and vendor_err.

RETURN VALUE
       On success, ibv_poll_cq() returns a non-negative value equal to the number of  completions
       found.  On failure, a negative value is returned.

NOTES
       Each polled completion is removed from the CQ and cannot be returned to it.

       The  user  should  consume work completions at a rate that prevents CQ overrun from occur-
       rence.  In case of a CQ overrun, the async event IBV_EVENT_CQ_ERR will be  triggered,  and
       the CQ cannot be used.

SEE ALSO
       ibv_post_send(3), ibv_post_recv(3)

AUTHORS
       Dotan Barak <dotanba@gmail.com>

libibverbs				    2006-10-31				   IBV_POLL_CQ(3)


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