1IBV_POLL_CQ(3)          Libibverbs Programmer's Manual          IBV_POLL_CQ(3)
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NAME

6       ibv_poll_cq - poll a completion queue (CQ)
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SYNOPSIS

9       #include <infiniband/verbs.h>
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11       int ibv_poll_cq(struct ibv_cq *cq, int num_entries,
12                       struct ibv_wc *wc);
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DESCRIPTION

15       ibv_poll_cq()  polls  the  CQ  cq  for work completions and returns the
16       first num_entries (or all available  completions  if  the  CQ  contains
17       fewer  than this number) in the array wc.  The argument wc is a pointer
18       to an array of ibv_wc structs, as defined in <infiniband/verbs.h>.
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20       struct ibv_wc {
21               uint64_t                wr_id;          /* ID of the completed Work Request (WR) */
22               enum ibv_wc_status      status;         /* Status of the operation */
23               enum ibv_wc_opcode      opcode;         /* Operation type specified in the completed WR */
24               uint32_t                vendor_err;     /* Vendor error syndrome */
25               uint32_t                byte_len;       /* Number of bytes transferred */
26               union {
27                       __be32                  imm_data;         /* Immediate data (in network byte order) */
28                       uint32_t                invalidated_rkey; /* Local RKey that was invalidated */
29               };
30               uint32_t                qp_num;         /* Local QP number of completed WR */
31               uint32_t                src_qp;         /* Source QP number (remote QP number) of completed WR (valid only for UD QPs) */
32               unsigned int            wc_flags;       /* Flags of the completed WR */
33               uint16_t                pkey_index;     /* P_Key index (valid only for GSI QPs) */
34               uint16_t                slid;           /* Source LID */
35               uint8_t                 sl;             /* Service Level */
36               uint8_t                 dlid_path_bits; /* DLID path bits (not applicable for multicast messages) */
37       };
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40       The attribute wc_flags describes the properties of the work completion.
41       It is either 0 or the bitwise OR of one or more of the following flags:
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43       IBV_WC_GRH  GRH is present (valid only for UD QPs)
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45       IBV_WC_WITH_IMM  Immediate data value is valid
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47       IBV_WC_WITH_INV   Invalidated  RKey data value is valid (cannot be com‐
48       bined with IBV_WC_WITH_IMM)
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50       IBV_WC_IP_CSUM_OK  TCP/UDP checksum over IPv4 and IPv4 header  checksum
51       are
52              verified.  Valid only when device_cap_flags in device_attr indi‐
53              cates current QP is supported by checksum offload.
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55       Not all wc attributes are always valid. If  the  completion  status  is
56       other  than  IBV_WC_SUCCESS,  only  the following attributes are valid:
57       wr_id, status, qp_num, and vendor_err.
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RETURN VALUE

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

64       Each polled completion is removed from the CQ and cannot be returned to
65       it.
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67       The user should consume work completions at a  rate  that  prevents  CQ
68       overrun  from  occurrence.   In  case  of a CQ overrun, the async event
69       IBV_EVENT_CQ_ERR will be triggered, and the CQ cannot be used.
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71       IBV_WC_DRIVER1 will be reported as a response to IBV_WR_DRIVER1 opcode;
72       IBV_WC_DRIVER2/IBV_WC_DRIVER3 will be reported on specific driver oper‐
73       ations.
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SEE ALSO

76       ibv_post_send(3), ibv_post_recv(3)
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AUTHORS

79       Dotan Barak <dotanba@gmail.com>
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83libibverbs                        2006-10-31                    IBV_POLL_CQ(3)