+/* by default set head/tail distance as 1/8 of ring capacity */
+#define HTD_MAX_DEF 8
+
+/* return the size of memory occupied by a ring */
+ssize_t
+rte_ring_get_memsize_elem(unsigned int esize, unsigned int count)
+{
+ ssize_t sz;
+
+ /* Check if element size is a multiple of 4B */
+ if (esize % 4 != 0) {
+ RTE_LOG(ERR, RING, "element size is not a multiple of 4\n");
+
+ return -EINVAL;
+ }
+
+ /* count must be a power of 2 */
+ if ((!POWEROF2(count)) || (count > RTE_RING_SZ_MASK )) {
+ RTE_LOG(ERR, RING,
+ "Requested number of elements is invalid, must be power of 2, and not exceed %u\n",
+ RTE_RING_SZ_MASK);
+
+ return -EINVAL;
+ }
+
+ sz = sizeof(struct rte_ring) + count * esize;
+ sz = RTE_ALIGN(sz, RTE_CACHE_LINE_SIZE);
+ return sz;
+}
+
+/* return the size of memory occupied by a ring */
+ssize_t
+rte_ring_get_memsize(unsigned int count)
+{
+ return rte_ring_get_memsize_elem(sizeof(void *), count);
+}
+
+/*
+ * internal helper function to reset prod/cons head-tail values.
+ */
+static void
+reset_headtail(void *p)
+{
+ struct rte_ring_headtail *ht;
+ struct rte_ring_hts_headtail *ht_hts;
+ struct rte_ring_rts_headtail *ht_rts;
+
+ ht = p;
+ ht_hts = p;
+ ht_rts = p;
+
+ switch (ht->sync_type) {
+ case RTE_RING_SYNC_MT:
+ case RTE_RING_SYNC_ST:
+ ht->head = 0;
+ ht->tail = 0;
+ break;
+ case RTE_RING_SYNC_MT_RTS:
+ ht_rts->head.raw = 0;
+ ht_rts->tail.raw = 0;
+ break;
+ case RTE_RING_SYNC_MT_HTS:
+ ht_hts->ht.raw = 0;
+ break;
+ default:
+ /* unknown sync mode */
+ RTE_ASSERT(0);
+ }
+}
+
+void
+rte_ring_reset(struct rte_ring *r)
+{
+ reset_headtail(&r->prod);
+ reset_headtail(&r->cons);
+}
+
+/*
+ * helper function, calculates sync_type values for prod and cons
+ * based on input flags. Returns zero at success or negative
+ * errno value otherwise.
+ */
+static int
+get_sync_type(uint32_t flags, enum rte_ring_sync_type *prod_st,
+ enum rte_ring_sync_type *cons_st)
+{
+ static const uint32_t prod_st_flags =
+ (RING_F_SP_ENQ | RING_F_MP_RTS_ENQ | RING_F_MP_HTS_ENQ);
+ static const uint32_t cons_st_flags =
+ (RING_F_SC_DEQ | RING_F_MC_RTS_DEQ | RING_F_MC_HTS_DEQ);
+
+ switch (flags & prod_st_flags) {
+ case 0:
+ *prod_st = RTE_RING_SYNC_MT;
+ break;
+ case RING_F_SP_ENQ:
+ *prod_st = RTE_RING_SYNC_ST;
+ break;
+ case RING_F_MP_RTS_ENQ:
+ *prod_st = RTE_RING_SYNC_MT_RTS;
+ break;
+ case RING_F_MP_HTS_ENQ:
+ *prod_st = RTE_RING_SYNC_MT_HTS;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ switch (flags & cons_st_flags) {
+ case 0:
+ *cons_st = RTE_RING_SYNC_MT;
+ break;
+ case RING_F_SC_DEQ:
+ *cons_st = RTE_RING_SYNC_ST;
+ break;
+ case RING_F_MC_RTS_DEQ:
+ *cons_st = RTE_RING_SYNC_MT_RTS;
+ break;
+ case RING_F_MC_HTS_DEQ:
+ *cons_st = RTE_RING_SYNC_MT_HTS;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+int
+rte_ring_init(struct rte_ring *r, const char *name, unsigned count,
+ unsigned flags)
+{
+ int ret;
+
+ /* compilation-time checks */
+ RTE_BUILD_BUG_ON((sizeof(struct rte_ring) &
+ RTE_CACHE_LINE_MASK) != 0);
+ RTE_BUILD_BUG_ON((offsetof(struct rte_ring, cons) &
+ RTE_CACHE_LINE_MASK) != 0);
+ RTE_BUILD_BUG_ON((offsetof(struct rte_ring, prod) &
+ RTE_CACHE_LINE_MASK) != 0);
+
+ RTE_BUILD_BUG_ON(offsetof(struct rte_ring_headtail, sync_type) !=
+ offsetof(struct rte_ring_hts_headtail, sync_type));
+ RTE_BUILD_BUG_ON(offsetof(struct rte_ring_headtail, tail) !=
+ offsetof(struct rte_ring_hts_headtail, ht.pos.tail));
+
+ RTE_BUILD_BUG_ON(offsetof(struct rte_ring_headtail, sync_type) !=
+ offsetof(struct rte_ring_rts_headtail, sync_type));
+ RTE_BUILD_BUG_ON(offsetof(struct rte_ring_headtail, tail) !=
+ offsetof(struct rte_ring_rts_headtail, tail.val.pos));
+
+ /* init the ring structure */
+ memset(r, 0, sizeof(*r));
+ ret = strlcpy(r->name, name, sizeof(r->name));
+ if (ret < 0 || ret >= (int)sizeof(r->name))
+ return -ENAMETOOLONG;
+ r->flags = flags;
+ ret = get_sync_type(flags, &r->prod.sync_type, &r->cons.sync_type);
+ if (ret != 0)
+ return ret;
+
+ if (flags & RING_F_EXACT_SZ) {
+ r->size = rte_align32pow2(count + 1);
+ r->mask = r->size - 1;
+ r->capacity = count;
+ } else {
+ if ((!POWEROF2(count)) || (count > RTE_RING_SZ_MASK)) {
+ RTE_LOG(ERR, RING,
+ "Requested size is invalid, must be power of 2, and not exceed the size limit %u\n",
+ RTE_RING_SZ_MASK);
+ return -EINVAL;
+ }
+ r->size = count;
+ r->mask = count - 1;
+ r->capacity = r->mask;
+ }
+
+ /* set default values for head-tail distance */
+ if (flags & RING_F_MP_RTS_ENQ)
+ rte_ring_set_prod_htd_max(r, r->capacity / HTD_MAX_DEF);
+ if (flags & RING_F_MC_RTS_DEQ)
+ rte_ring_set_cons_htd_max(r, r->capacity / HTD_MAX_DEF);
+
+ return 0;
+}
+
+/* create the ring for a given element size */