[dpdk-dev] [RFC 1/6] ethdev: add min/max MTU to device info

[Ian Stokes]

From: Stephen Hemminger <stephen at networkplumber.org>

This addresses the usability issue raised by OVS at DPDK Userspace
summit. It adds general min/max mtu into device info. For compatiablity,
and to save space, it fits in a hole in existing structure.

The initial version sets max mtu to normal Ethernet, it is up to
PMD to set larger value if it supports Jumbo frames.

Also remove the deprecation notice introduced in 18.11 regarding this
change.

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
Signed-off-by: Ian Stokes <ian.stokes at intel.com>
---
 doc/guides/rel_notes/deprecation.rst | 12 ------------
 lib/librte_ethdev/rte_ethdev.c       |  7 +++++++
 lib/librte_ethdev/rte_ethdev.h       |  2 ++
 3 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index 1b4fcb7e6..0e85c47f3 100644
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -56,18 +56,6 @@ 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.
-
 * meter: New ``rte_color`` definition will be added in 19.02 and that will
   replace ``enum rte_meter_color`` in meter library in 19.05. This will help
   to consolidate color definition, which is currently replicated in many places,
diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
index 0d192a24b..f089af94d 100644
--- a/lib/librte_ethdev/rte_ethdev.c
+++ b/lib/librte_ethdev/rte_ethdev.c
@@ -2527,6 +2527,8 @@ rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info *dev_info)
 	dev_info->rx_desc_lim = lim;
 	dev_info->tx_desc_lim = lim;
 	dev_info->device = dev->device;
+	dev_info->min_mtu = ETHER_MIN_MTU;
+	dev_info->max_mtu = ETHER_MTU;
 
 	RTE_FUNC_PTR_OR_RET(*dev->dev_ops->dev_infos_get);
 	(*dev->dev_ops->dev_infos_get)(dev, dev_info);
@@ -2590,12 +2592,17 @@ int
 rte_eth_dev_set_mtu(uint16_t port_id, uint16_t mtu)
 {
 	int ret;
+	struct rte_eth_dev_info dev_info;
 	struct rte_eth_dev *dev;
 
 	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
 	dev = &rte_eth_devices[port_id];
 	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->mtu_set, -ENOTSUP);
 
+	rte_eth_dev_info_get(port_id, &dev_info);
+	if (mtu < dev_info.min_mtu || mtu > dev_info.max_mtu)
+		return -EINVAL;
+
 	ret = (*dev->dev_ops->mtu_set)(dev, mtu);
 	if (!ret)
 		dev->data->mtu = mtu;
diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
index a3c864a13..9fe51b2bd 100644
--- a/lib/librte_ethdev/rte_ethdev.h
+++ b/lib/librte_ethdev/rte_ethdev.h
@@ -1086,6 +1086,8 @@ struct rte_eth_dev_info {
 	const char *driver_name; /**< Device Driver name. */
 	unsigned int if_index; /**< Index to bound host interface, or 0 if none.
 		Use if_indextoname() to translate into an interface name. */
+	uint16_t min_mtu;	/**< Minimum MTU allowed */
+	uint16_t max_mtu;	/**< Maximum MTU allowed */
 	const uint32_t *dev_flags; /**< Device flags */
 	uint32_t min_rx_bufsize; /**< Minimum size of RX buffer. */
 	uint32_t max_rx_pktlen; /**< Maximum configurable length of RX pkt. */
-- 
2.13.6