Re: [dpdk-dev] [RFC] ethdev: add new offload flag to keep CRC

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 06/09/2018 01:57 AM, Ferruh Yigit wrote:
> DEV_RX_OFFLOAD_KEEP_CRC offload flag added.
>
> DEV_RX_OFFLOAD_CRC_STRIP flag will remain one more release
> default behavior in PMDs is to keep the CRC until this flag removed
>
> Until DEV_RX_OFFLOAD_CRC_STRIP flag is removed:
> - Setting both KEEP_CRC & CRC_STRIP is INVALID

ethdev layer should enforce it.

> - Setting only CRC_STRIP PMD should strip the CRC
> - Setting only KEEP_CRC PMD should keep the CRC
> - Not setting both PMD should keep the CRC
>
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>

- rte_rx_offload_names should be updated as well
- testpmd should be updated

I'm not sure that I understand the transition plan. I think PMDs which 
support
KEEP_CRC should be updated by the patch to advertise the offload. Otherwise,
generic checks in ethdev will not allow to enable it. Other option is to 
simply
drop it on ethdev layer (since basically it changes nothing for PMD now) and
encourage PMD maintainers to advertise and take it into account if the 
feature
is supported (however, if the bit is dropped on ethdev layer, the code 
would
be unused/dead regardless application request). Too complicated. I guess
there are not so many PMDs which support KEEP_CRC. Better to update them.

The patch should encourage applications which would like to keep CRC to
use the offload since the next release will drop CRC_STRIP and it will
change behaviour (no KEEP_CRC => strip it)