Hi Tom,
> -----Original Message-----
> From: Tom Rix <t...@redhat.com>
> Sent: Thursday, July 7, 2022 6:34 AM
> To: Chautru, Nicolas <nicolas.chau...@intel.com>; dev@dpdk.org;
> tho...@monjalon.net; gak...@marvell.com; hemant.agra...@nxp.com
> Cc: maxime.coque...@redhat.com; m...@ashroe.eu; Richardson, Bruce
> <bruce.richard...@intel.com>; david.march...@redhat.com;
> step...@networkplumber.org
> Subject: Re: [PATCH v4 3/7] bbdev: add device info on queue topology
>
>
> On 7/6/22 2:12 PM, Chautru, Nicolas wrote:
> > Hi Tom,
> >
> >> -----Original Message-----
> >> From: Tom Rix <t...@redhat.com>
> >> Subject: Re: [PATCH v4 3/7] bbdev: add device info on queue topology
> >>
> >>
> >> On 7/5/22 5:23 PM, Nicolas Chautru wrote:
> >>> Adding more options in the API to expose the number of queues
> >>> exposed and related priority.
> >>>
> >>> Signed-off-by: Nicolas Chautru <nicolas.chau...@intel.com>
> >>> ---
> >>> lib/bbdev/rte_bbdev.h | 4 ++++
> >>> 1 file changed, 4 insertions(+)
> >>>
> >>> diff --git a/lib/bbdev/rte_bbdev.h b/lib/bbdev/rte_bbdev.h index
> >>> 9b1ffa4..ac941d6 100644
> >>> --- a/lib/bbdev/rte_bbdev.h
> >>> +++ b/lib/bbdev/rte_bbdev.h
> >>> @@ -289,6 +289,10 @@ struct rte_bbdev_driver_info {
> >>>
> >>> /** Maximum number of queues supported by the device */
> >>> unsigned int max_num_queues;
> >>> + /** Maximum number of queues supported per operation type */
> >>> + unsigned int num_queues[RTE_BBDEV_OP_TYPE_PADDED_MAX];
> >>> + /** Priority level supported per operation type */
> >>> + unsigned int queue_priority[RTE_BBDEV_OP_TYPE_PADDED_MAX];
> >> It is better to add new elements to the end of a structure for better
> >> backward compatibility
> > All that serie is not ABI compatible (sizes change etc...). I don’t believe
> > there
> is such a recommendation, is there?
>
> Depends on what users expect, a dynamically linked old application would at
> best core here. If the elements were added to the end, yes the size would
> change but the old dynamically linked application would not use
> them. Dynamically linking is nice because problems in the library can be
> fixed
> and shipped without forcing the user recompile. Though the user may not
> realize it, this change forces them to recompile.
>
> Tom
Thanks Tom. In that very context, the change are big enough not to have any
form of compatibility. This a new ABI version, and user knows they will have to
recompile.
Still it would be great to capture a recommendation in DPDK coding guideline in
case there is such a BKM, I have heard multiple arguments for different
preference, if we want to harmonize such things let's capture in coding guide
lines, it would not hurt. Maybe one for Thomas?
>
> >
> >> Tom
> >>
> >>> /** Queue size limit (queue size must also be power of 2) */
> >>> uint32_t queue_size_lim;
> >>> /** Set if device off-loads operation to hardware */
