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doc: announce deprecation of maximum Rx length field

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The configuration related to the MTU is complex
and have some design issues.
This area should be redesigned a bit.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Acked-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Acked-by: Matan Azrad <matan@nvidia.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
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Ferruh Yigit 2020-11-24 17:36:28 +00:00 committed by Thomas Monjalon
parent 7f01375166
commit df18819356
1 changed files with 25 additions and 0 deletions
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doc/guides/rel_notes/deprecation.rst
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@ -64,6 +64,31 @@ Deprecation Notices
In 19.11 PMDs will still update the field even when the offload is not
enabled.
* ethdev: ``uint32_t max_rx_pkt_len`` field of ``struct rte_eth_rxmode``, will be
replaced by a new ``uint32_t mtu`` field of ``struct rte_eth_conf`` in v21.11.
The new ``mtu`` field will be used to configure the initial device MTU via
``rte_eth_dev_configure()`` API.
Later MTU can be changed by ``rte_eth_dev_set_mtu()`` API as done now.
The existing ``(struct rte_eth_dev)->data->mtu`` variable will be used to store
the configured ``mtu`` value,
and this new ``(struct rte_eth_dev)->data->dev_conf.mtu`` variable will
be used to store the user configuration request.
Unlike ``max_rx_pkt_len``, which was valid only when ``JUMBO_FRAME`` enabled,
``mtu`` field will be always valid.
When ``mtu`` config is not provided by the application, default ``RTE_ETHER_MTU``
value will be used.
``(struct rte_eth_dev)->data->mtu`` should be updated after MTU set successfully,
either by ``rte_eth_dev_configure()`` or ``rte_eth_dev_set_mtu()``.
An application may need to configure device for a specific Rx packet size, like for
cases ``DEV_RX_OFFLOAD_SCATTER`` is not supported and device received packet size
can't be bigger than Rx buffer size.
To cover these cases an application needs to know the device packet overhead to be
able to calculate the ``mtu`` corresponding to a Rx buffer size, for this
``(struct rte_eth_dev_info).max_rx_pktlen`` will be kept,
the device packet overhead can be calculated as:
``(struct rte_eth_dev_info).max_rx_pktlen - (struct rte_eth_dev_info).max_mtu``
* ethdev: ``rx_descriptor_done`` dev_ops and ``rte_eth_rx_descriptor_done``
will be removed in 21.11.
Existing ``rte_eth_rx_descriptor_status`` and ``rte_eth_tx_descriptor_status``