[PATCH v2 1/2] mbuf: add function returning default buffer address

[Yongseok Koh <yskoh@mellanox.com>]

This patch introduces two new functions - rte_mbuf_buf_addr_default() and
rte_mbuf_data_baddr_default().

rte_mbuf_buf_addr_default() reutrns the default buffer address of given
mbuf which comes after mbuf structure and private data.

rte_mbuf_data_baddr_default() returns the default address of mbuf data
taking the headroom into account.

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
---

v2:
* initial implementation

 lib/librte_mbuf/rte_mbuf.h | 43 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index bc562dc8a9..6c4c1bd3e8 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -788,8 +788,47 @@ rte_mbuf_from_indirect(struct rte_mbuf *mi)
 }
 
 /**
+ * Return the default buffer address of the mbuf.
+ *
+ * @param mb
+ *   The pointer to the mbuf.
+ * @param mp
+ *   The pointer to the mempool of the mbuf.
+ * @return
+ *   The pointer of the mbuf buffer.
+ */
+static inline char *
+rte_mbuf_buf_addr_default(struct rte_mbuf *mb, struct rte_mempool *mp)
+{
+	char *buffer_addr;
+
+	buffer_addr = (char *)mb + sizeof(*mb) + rte_pktmbuf_priv_size(mp);
+	return buffer_addr;
+}
+
+
+/**
+ * Return the default address of the beginning of the mbuf data.
+ *
+ * @param mb
+ *   The pointer to the mbuf.
+ * @return
+ *   The pointer of the beginning of the mbuf data.
+ */
+static inline char *
+rte_mbuf_data_baddr_default(struct rte_mbuf *mb)
+{
+	return rte_mbuf_buf_addr_default(mb, mb->pool) + RTE_PKTMBUF_HEADROOM;
+}
+
+/**
  * Return the buffer address embedded in the given mbuf.
  *
+ * Note that accessing mempool pointer of a mbuf is expensive because the
+ * pointer is stored in the 2nd cache line of mbuf. If mempool is known, it
+ * is better not to reference the mempool pointer in mbuf but calling
+ * rte_mbuf_buf_addr_default() would be more efficient.
+ *
  * @param md
  *   The pointer to the mbuf.
  * @return
@@ -798,9 +837,7 @@ rte_mbuf_from_indirect(struct rte_mbuf *mi)
 static inline char *
 rte_mbuf_to_baddr(struct rte_mbuf *md)
 {
-	char *buffer_addr;
-	buffer_addr = (char *)md + sizeof(*md) + rte_pktmbuf_priv_size(md->pool);
-	return buffer_addr;
+	return rte_mbuf_buf_addr_default(md, md->pool);
 }
 
 /**
-- 
2.11.0