[dpdk-dev] [PATCH v5 1/2] mbuf: add function returning buffer address

[Yongseok Koh <yskoh@mellanox.com>]

This patch introduces two new functions - rte_mbuf_buf_addr() and
rte_mbuf_data_addr_default().

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

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

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
---

v5:
* add more comment regarding mp arg
* use ALLOW_EXPERIMENTAL_API for rte_mbuf_to_baddr()

v4:
* fix compilation error due to the experimental tag
* add warning of experimental tag to the comments

v3:
* rename functions

v2:
* initial implementation

 lib/librte_mbuf/rte_mbuf.h | 54 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index bc562dc8a9..4a03d5e6fc 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -788,7 +788,55 @@ rte_mbuf_from_indirect(struct rte_mbuf *mi)
 }
 
 /**
- * Return the buffer address embedded in the given mbuf.
+ * Return address of buffer embedded in the given mbuf.
+ *
+ * The return value shall be same as mb->buf_addr if the mbuf is already
+ * initialized and direct. However, this API is useful if mempool of the
+ * mbuf is already known because it doesn't need to access mbuf contents in
+ * order to get the mempool pointer.
+ *
+ * @warning
+ * @b EXPERIMENTAL: This API may change without prior notice.
+ * This will be used by rte_mbuf_to_baddr() which has redundant code once
+ * experimental tag is removed.
+ *
+ * @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_experimental
+rte_mbuf_buf_addr(struct rte_mbuf *mb, struct rte_mempool *mp)
+{
+	return (char *)mb + sizeof(*mb) + rte_pktmbuf_priv_size(mp);
+}
+
+/**
+ * Return the default address of the beginning of the mbuf data.
+ *
+ * @warning
+ * @b EXPERIMENTAL: This API may change without prior notice.
+ *
+ * @param mb
+ *   The pointer to the mbuf.
+ * @return
+ *   The pointer of the beginning of the mbuf data.
+ */
+static inline char * __rte_experimental
+rte_mbuf_data_addr_default(struct rte_mbuf *mb)
+{
+	return rte_mbuf_buf_addr(mb, mb->pool) + RTE_PKTMBUF_HEADROOM;
+}
+
+/**
+ * Return address of buffer embedded in the given mbuf.
+ *
+ * @note: 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() would be more efficient.
  *
  * @param md
  *   The pointer to the mbuf.
@@ -798,9 +846,13 @@ rte_mbuf_from_indirect(struct rte_mbuf *mi)
 static inline char *
 rte_mbuf_to_baddr(struct rte_mbuf *md)
 {
+#ifdef ALLOW_EXPERIMENTAL_API
+	return rte_mbuf_buf_addr(md, md->pool);
+#else
 	char *buffer_addr;
 	buffer_addr = (char *)md + sizeof(*md) + rte_pktmbuf_priv_size(md->pool);
 	return buffer_addr;
+#endif
 }
 
 /**
-- 
2.11.0