+/**
+ * Handle scattered buffers for mlx4_tx_burst().
+ *
+ * @param txq
+ * TX queue structure.
+ * @param segs
+ * Number of segments in buf.
+ * @param elt
+ * TX queue element to fill.
+ * @param[in] buf
+ * Buffer to process.
+ * @param elts_head
+ * Index of the linear buffer to use if necessary (normally txq->elts_head).
+ * @param[out] sges
+ * Array filled with SGEs on success.
+ *
+ * @return
+ * A structure containing the processed packet size in bytes and the
+ * number of SGEs. Both fields are set to (unsigned int)-1 in case of
+ * failure.
+ */
+static struct tx_burst_sg_ret {
+ unsigned int length;
+ unsigned int num;
+}
+tx_burst_sg(struct txq *txq, unsigned int segs, struct txq_elt *elt,
+ struct rte_mbuf *buf, unsigned int elts_head,
+ struct ibv_sge (*sges)[MLX4_PMD_SGE_WR_N])
+{
+ unsigned int sent_size = 0;
+ unsigned int j;
+ int linearize = 0;
+
+ /* When there are too many segments, extra segments are
+ * linearized in the last SGE. */
+ if (unlikely(segs > elemof(*sges))) {
+ segs = (elemof(*sges) - 1);
+ linearize = 1;
+ }
+ /* Update element. */
+ elt->buf = buf;
+ /* Register segments as SGEs. */
+ for (j = 0; (j != segs); ++j) {
+ struct ibv_sge *sge = &(*sges)[j];
+ uint32_t lkey;
+
+ /* Retrieve Memory Region key for this memory pool. */
+ lkey = txq_mp2mr(txq, buf->pool);
+ if (unlikely(lkey == (uint32_t)-1)) {
+ /* MR does not exist. */
+ DEBUG("%p: unable to get MP <-> MR association",
+ (void *)txq);
+ /* Clean up TX element. */
+ elt->buf = NULL;
+ goto stop;
+ }
+ /* Update SGE. */
+ sge->addr = rte_pktmbuf_mtod(buf, uintptr_t);
+ if (txq->priv->vf)
+ rte_prefetch0((volatile void *)
+ (uintptr_t)sge->addr);
+ sge->length = DATA_LEN(buf);
+ sge->lkey = lkey;
+ sent_size += sge->length;
+ buf = NEXT(buf);
+ }
+ /* If buf is not NULL here and is not going to be linearized,
+ * nb_segs is not valid. */
+ assert(j == segs);
+ assert((buf == NULL) || (linearize));
+ /* Linearize extra segments. */
+ if (linearize) {
+ struct ibv_sge *sge = &(*sges)[segs];
+ linear_t *linear = &(*txq->elts_linear)[elts_head];
+ unsigned int size = linearize_mbuf(linear, buf);
+
+ assert(segs == (elemof(*sges) - 1));
+ if (size == 0) {
+ /* Invalid packet. */
+ DEBUG("%p: packet too large to be linearized.",
+ (void *)txq);
+ /* Clean up TX element. */
+ elt->buf = NULL;
+ goto stop;
+ }
+ /* If MLX4_PMD_SGE_WR_N is 1, free mbuf immediately. */
+ if (elemof(*sges) == 1) {
+ do {
+ struct rte_mbuf *next = NEXT(buf);
+
+ rte_pktmbuf_free_seg(buf);
+ buf = next;
+ } while (buf != NULL);
+ elt->buf = NULL;
+ }
+ /* Update SGE. */
+ sge->addr = (uintptr_t)&(*linear)[0];
+ sge->length = size;
+ sge->lkey = txq->mr_linear->lkey;
+ sent_size += size;
+ }
+ return (struct tx_burst_sg_ret){
+ .length = sent_size,
+ .num = segs,
+ };
+stop:
+ return (struct tx_burst_sg_ret){
+ .length = -1,
+ .num = -1,
+ };
+}
+
+#endif /* MLX4_PMD_SGE_WR_N > 1 */
+