[dpdk-dev] [PATCH 08/13] mbuf: add named points inside the mbuf structure

[Bruce Richardson <bruce.richardson@intel.com>]

Add markers or "labels" at given points inside the mbuf which can be
used instead of individual fields to identify the start of logical
sections inside the mbuf.

The use of typedefs and dummy fields was chosen over using unions
because of a couple reasons:
* unions cause an extra level of indentation (more likely two levels as
  a union containing a struct for multiple fields would be needed). This
  makes the lines longer than they need to be and increases the need for
  wrapping. [This was the main reason]
* with markers, you can apply multiple markers at the same point if
  wanted.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
 lib/librte_mbuf/rte_mbuf.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index ca66d9a..591be95 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -115,14 +115,22 @@ extern "C" {
  */
 #define PKT_TX_OFFLOAD_MASK (PKT_TX_VLAN_PKT | PKT_TX_IP_CKSUM | PKT_TX_L4_MASK)
 
+/* define a set of marker types that can be used to refer to set points in the
+ * mbuf */
+typedef void    *MARKER[0];   /**< generic marker for a point in a structure */
+typedef uint64_t MARKER64[0]; /**< marker that allows us to overwrite 8 bytes
+                               * with a single assignment */
 /**
  * The generic rte_mbuf, containing a packet mbuf.
  */
 struct rte_mbuf {
+	MARKER cacheline0;
+
 	void *buf_addr;           /**< Virtual address of segment buffer. */
 	phys_addr_t buf_physaddr; /**< Physical address of segment buffer. */
 
 	/* next 8 bytes are initialised on RX descriptor rearm */
+	MARKER64 rearm_data;
 	uint16_t buf_len;         /**< Length of segment buffer. */
 	uint16_t data_off;
 
@@ -147,6 +155,7 @@ struct rte_mbuf {
 	uint64_t ol_flags;      /**< Offload features. */
 
 	/* remaining bytes are set on RX when pulling packet from descriptor */
+	MARKER rx_descriptor_fields1;
 	uint16_t packet_type;   /**< Type of packet, e.g. protocols used */
 	uint16_t data_len;      /**< Amount of data in segment buffer. */
 	uint32_t pkt_len;       /**< Total pkt len: sum of all segments. */
-- 
1.9.3