[dpdk-dev] [RFC] doc: announce max Rx packet len field deprecation
Ferruh Yigit
ferruh.yigit at intel.com
Wed Oct 21 18:28:30 CEST 2020
On 10/21/2020 4:10 PM, Andrew Rybchenko wrote:
> On 10/21/20 1:18 PM, Ananyev, Konstantin wrote:
>>> 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>
>
> Do we really need the field in either rte_eth_rxmode or rte_eth_conf?
> What's the point of duplication? We have dedicated API to get/set
> which could be called in stopped state, set value saved in
> data->mtu and used by the driver at start up and Rx queues setup
> (to check scatter vs data room in mbuf consistency).
>
Not sure if we really need it, I had same thought.
The benefit of having it is, user can configure the Rx packet size within the
``rte_eth_dev_configure()`` API, without it user will need to call the
``rte_eth_dev_set_mtu()`` API explicitly, which will add another mandatory call
to the device initialization, so I think having this fields simplifies the
initialization.
Having it has the duplication problem, same thing configured by two different APIs.
>>> + 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
>
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