Re: [dpdk-dev] [v4 1/3] cryptodev: support enqueue callback functions

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> 
> Hi Tech board members,
> 
> Could you please clarify the concern?
> The latest patch (https://patches.dpdk.org/patch/82536/) supports both enqueue and dequeue callback functionality.
> 
> Thanks
> Abhinandan
> 
> > -----Original Message-----
> > From: Akhil Goyal <akhil.goyal@nxp.com>
> > Sent: Tuesday, October 27, 2020 11:59 PM
> > To: Gujjar, Abhinandan S <abhinandan.gujjar@intel.com>; dev@dpdk.org;
> > Doherty, Declan <declan.doherty@intel.com>;
> > Honnappa.Nagarahalli@arm.com; Ananyev, Konstantin
> > <konstantin.ananyev@intel.com>; techboard@dpdk.org
> > Cc: Vangati, Narender <narender.vangati@intel.com>; jerinj@marvell.com
> > Subject: RE: [v4 1/3] cryptodev: support enqueue callback functions
> >
> > Hi Tech board members,
> >
> > I have a doubt about the ABI breakage in below addition of field.
> > Could you please comment.
> >
> > >  /** The data structure associated with each crypto device. */  struct
> > > rte_cryptodev {
> > >  	dequeue_pkt_burst_t dequeue_burst;
> > > @@ -867,6 +922,10 @@ struct rte_cryptodev {
> > >  	__extension__
> > >  	uint8_t attached : 1;
> > >  	/**< Flag indicating the device is attached */
> > > +
> > > +	struct rte_cryptodev_enq_cb_rcu *enq_cbs;
> > > +	/**< User application callback for pre enqueue processing */
> > > +
> > >  } __rte_cache_aligned;
> >
> > Here rte_cryptodevs is defined in stable API list in map file which is a pointer
> > To all rte_cryptodev and the above change is changing the size of the structure.

While this patch adds new fields into rte_cryptodev structure,
it doesn't change the size of it.
struct rte_cryptodev is cache line aligned, so it's current size:
128B for 64-bit systems, and 64B(/128B) for 32-bit systems.
So for 64-bit we have 47B implicitly reserved, and for 32-bit we have 19B reserved.
That's enough to add two pointers without changing size of this struct. 

> > IMO, it seems an ABI breakage, but not sure. So wanted to double check.
> > Now if it is an ABI breakage, then can we allow it? There was no deprecation
> > notice Prior to this release.

Yes, there was no deprecation note in advance.
Though I think the risk is minimal - size of the struct will remain unchanged (see above).
My vote to let it in for 20.11.

> > Also I think if we are allowing the above change, then we should also add
> > another Field for deq_cbs also for post crypto processing in this patch only.

+1 for this.
I think it was already addressed in v5.

Konstantin