[dpdk-dev] [PATCH] doc: announce ABI change for rte_eth_dev structure

[Vlad Zolotarov]

On 07/31/2016 10:46 AM, Vlad Zolotarov wrote:
>
>
> On 07/20/2016 05:24 PM, Tomasz Kulasek wrote:
>> This is an ABI deprecation notice for DPDK 16.11 in librte_ether about
>> changes in rte_eth_dev and rte_eth_desc_lim structures.
>>
>> In 16.11, we plan to introduce rte_eth_tx_prep() function to do
>> necessary preparations of packet burst to be safely transmitted on
>> device for desired HW offloads (set/reset checksum field according to
>> the hardware requirements) and check HW constraints (number of segments
>> per packet, etc).
>>
>> While the limitations and requirements may differ for devices, it
>> requires to extend rte_eth_dev structure with new function pointer
>> "tx_pkt_prep" which can be implemented in the driver to prepare and
>> verify packets, in devices specific way, before burst, what should to
>> prevent application to send malformed packets.
>>
>> Also new fields will be introduced in rte_eth_desc_lim: nb_seg_max and
>> nb_mtu_seg_max, providing an information about max segments in TSO and
>> non TSO packets acceptable by device.
>>
>> Signed-off-by: Tomasz Kulasek <tomaszx.kulasek at intel.com>
>
> Acked-by: Vlad Zolotarov <vladz at scylladb.com>

One small comment however.
Although this function is a must we need a way to clearly understand 
which one the clusters are malformed since dropping the whole bulk is 
usually not an option and sending the malformed packets anyway may cause 
a HW hang, thus not an option as well.
Another thing - I've pulled the current master and I couldn't find the 
way an application may query the mentioned Tx offload HW limitation, 
e.g. maximum number of segments.
Knowing this limitation would avoid extra liniarization.

thanks,
vlad

>
>> ---
>>   doc/guides/rel_notes/deprecation.rst |    7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/doc/guides/rel_notes/deprecation.rst 
>> b/doc/guides/rel_notes/deprecation.rst
>> index f502f86..485aacb 100644
>> --- a/doc/guides/rel_notes/deprecation.rst
>> +++ b/doc/guides/rel_notes/deprecation.rst
>> @@ -41,3 +41,10 @@ Deprecation Notices
>>   * The mempool functions for single/multi producer/consumer are 
>> deprecated and
>>     will be removed in 16.11.
>>     It is replaced by rte_mempool_generic_get/put functions.
>> +
>> +* In 16.11 ABI changes are plained: the ``rte_eth_dev`` structure 
>> will be
>> +  extended with new function pointer ``tx_pkt_prep`` allowing 
>> verification
>> +  and processing of packet burst to meet HW specific requirements 
>> before
>> +  transmit. Also new fields will be added to the 
>> ``rte_eth_desc_lim`` structure:
>> +  ``nb_seg_max`` and ``nb_mtu_seg_max`` provideing information about 
>> number of
>> +  segments limit to be transmitted by device for TSO/non-TSO packets.
>