[dpdk-dev] [RFC] doc: announce max Rx packet len field deprecation

[Ananyev, Konstantin]

> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit at intel.com>
> ---
> Cc: Thomas Monjalon <thomas at monjalon.net>
> Cc: Andrew Rybchenko <arybchenko at solarflare.com>
> Cc: Konstantin Ananyev <konstantin.ananyev at intel.com>
> Cc: Matan Azrad <matan at nvidia.com>
> Cc: Olivier Matz <olivier.matz at 6wind.com>
> Cc: Jerin Jacob <jerinj at marvell.com>
> ---
>  doc/guides/rel_notes/deprecation.rst | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
> index 8ceb385141..d4a31392d3 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -149,6 +149,31 @@ Deprecation Notices
>    will be limited to maximum 256 queues.
>    Also compile time flag ``RTE_ETHDEV_QUEUE_STAT_CNTRS`` will be removed.
> 
> +* ethdev: In ``struct rte_eth_rxmode``, ``uint32_t max_rx_pkt_len`` will be
> +  replaced by a new ``uint32_t mtu`` in v21.11.

Probably no point to keep mtu value in rte_eth_rxmode.
Better to move it to rte_eth_conf.
Apart from that: +1 for this change.
Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>

> +  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.rxmode.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.
> +  Driver is responsible from updating ``(struct rte_eth_dev)->data->mtu`` after MTU
> +  set successfully, either by ``rte_eth_dev_configure()`` or ``rte_eth_dev_set_mtu()``.
> +
> +  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 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``
> +
>  * cryptodev: support for using IV with all sizes is added, J0 still can
>    be used but only when IV length in following structs ``rte_crypto_auth_xform``,
>    ``rte_crypto_aead_xform`` is set to zero. When IV length is greater or equal
> --
> 2.26.2