[dpdk-dev] [PATCH v2] doc: announce ABI change for rte_eth_dev structure

[Ananyev, Konstantin]

> -----Original Message-----
> From: Jerin Jacob [mailto:jerin.jacob at caviumnetworks.com]
> Sent: Wednesday, July 27, 2016 6:11 PM
> To: Thomas Monjalon <thomas.monjalon at 6wind.com>
> Cc: Kulasek, TomaszX <tomaszx.kulasek at intel.com>; dev at dpdk.org; Ananyev, Konstantin <konstantin.ananyev at intel.com>
> Subject: Re: [dpdk-dev] [PATCH v2] doc: announce ABI change for rte_eth_dev structure
> 
> On Wed, Jul 27, 2016 at 01:59:01AM -0700, Thomas Monjalon wrote:
> > > > Signed-off-by: Tomasz Kulasek <tomaszx.kulasek at intel.com>
> > > > ---
> > > > +* 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.
> > >
> > > Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
> >
> > I think I understand you want to split the TX processing:
> > 	1/ modify/write in mbufs
> > 	2/ write in HW
> > and let application decide:
> > 	- where the TX prep is done (which core)
> 
> In what basics applications knows when and where to call tx_pkt_prep in fast path.
> if all the time it needs to call before tx_burst then the PMD won't have/don't need this callback waste cycles in fast path.Is this the expected
> behavior ?
> Anything think it as compile time to make other PMDs wont suffer because of this change.

Not sure what suffering you are talking about...
Current model - i.e. when application does preparations (or doesn't if none is required)
on its own and just call tx_burst() would still be there.
If the app doesn't want to use tx_prep() by some reason - that still ok,
and decision is up to the particular app. 
Konstantin

> 
> 
> > 	- what to do if the TX prep fail
> > So adding some processing in this first part becomes "not too
> > expensive" or "manageable" from the application point of view.
> >
> > If I well understand the intent,
> >
> > Acked-by: Thomas Monjalon <thomas.monjalon at 6wind.com> (except typos ;)