doc: announce ethdev ABI change for MTU limits info

Maximum and minimum MTU values vary between hardware devices. In
hardware agnostic DPDK applications access to such information would
allow a more accurate way of validating and setting supported MTU values on
a per device basis rather than using a defined default for all devices.

The following solution was proposed:

http://mails.dpdk.org/archives/dev/2018-September/110959.html

This patch adds a depreciation notice for ``rte_eth_dev_info`` as new
members will be added to represent min and max MTU values. These can be
added to fit a hole in the existing structure for amd64 but not for 32 bit,
as such ABI change will occur as size of the structure will be impacted.

Signed-off-by: Ian Stokes <ian.stokes@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>

diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index 08557b9..27ede77 100644 (file)
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -63,6 +63,18 @@ Deprecation Notices
   Target release for removal of the legacy API will be defined once most
   PMDs have switched to rte_flow.
 
+* ethdev: Maximum and minimum MTU values vary between hardware devices. In
+  hardware agnostic DPDK applications access to such information would allow
+  a more accurate way of validating and setting supported MTU values on a per
+  device basis rather than using a defined default for all devices. To
+  resolve this, the following members will be added to ``rte_eth_dev_info``.
+  Note: these can be added to fit a hole in the existing structure for amd64
+  but not for 32-bit, as such ABI change will occur as size of the structure
+  will increase.
+
+  - Member ``uint16_t min_mtu`` the minimum MTU allowed.
+  - Member ``uint16_t max_mtu`` the maximum MTU allowed.
+
 * pdump: As we changed to use generic IPC, some changes in APIs and structure
   are expected in subsequent release.