doc: announce ethdev API change for preferred burst size

rte_eth_rx_burst(..,nb_pkts) function has semantic that if return value
is smaller than requested, application can consider it end of packet
stream. Some hardware can only support smaller burst sizes which need
to be advertised. Similar is the case for Tx burst.

This patch adds deprecation notice for rte_eth_dev_info structure as
new members, for preferred Rx and Tx burst and ring size would be
added - impacting the size of the structure.

Signed-off-by: Shreyansh Jain <shreyansh.jain@nxp.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Zhiyong Yang <zhiyong.yang@intel.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>

diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index 149bf23..05436b2 100644 (file)
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -115,6 +115,19 @@ Deprecation Notices
   The new API add rss_level field to ``rte_eth_rss_conf`` to enable a choice
   of RSS hash calculation on outer or inner header of tunneled packet.
 
+* ethdev:  Currently, if the  rte_eth_rx_burst() function returns a value less
+  than *nb_pkts*, the application will assume that no more packets are present.
+  Some of the hw queue based hardware can only support smaller burst for RX
+  and TX and thus break the expectation of the rx_burst API. Similar is the
+  case for TX burst as well as ring sizes. ``rte_eth_dev_info`` will be added
+  with following new parameters so as to support semantics for drivers to
+  define a preferred size for Rx/Tx burst and rings.
+
+  - Member ``struct preferred_size`` would be added to enclose all preferred
+    size to be fetched from driver/implementation.
+  - Members ``uint16_t rx_burst``,  ``uint16_t tx_burst``, ``uint16_t rx_ring``,
+    and ``uint16_t tx_ring`` would be added to ``struct preferred_size``.
+
 * i40e: The default flexible payload configuration which extracts the first 16
   bytes of the payload for RSS will be deprecated starting from 18.02. If
   required the previous behavior can be configured using existing flow