doc: announce ABI change for mbuf structure

For 16.11, the mbuf structure will be modified implying ABI breakage.
Some discussions already took place here:
http://www.dpdk.org/dev/patchwork/patch/12878/

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Acked-by: John Daley <johndale@cisco.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>

diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index a805ca7..d1067ba 100644 (file)
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -33,6 +33,12 @@ Deprecation Notices
   do not need to care about the kind of devices that are being used, making it
   easier to add new buses later.
 
+* ABI changes are planned for 16.11 in the ``rte_mbuf`` structure: some fields
+  may be reordered to facilitate the writing of ``data_off``, ``refcnt``, and
+  ``nb_segs`` in one operation, because some platforms have an overhead if the
+  store address is not naturally aligned. Other mbuf fields, such as the
+  ``port`` field, may be moved or removed as part of this mbuf work.
+
 * The mbuf flags PKT_RX_VLAN_PKT and PKT_RX_QINQ_PKT are deprecated and
   are respectively replaced by PKT_RX_VLAN_STRIPPED and
   PKT_RX_QINQ_STRIPPED, that are better described. The old flags and