Hi Thomas,
> -----Original Message-----
> From: Thomas Monjalon <tho...@monjalon.net>
> Sent: Monday, March 16, 2020 2:09 PM
> To: Trahe, Fiona <fiona.tr...@intel.com>
> Cc: Kusztal, ArkadiuszX <arkadiuszx.kusz...@intel.com>; David Marchand
> <david.march...@redhat.com>; nhor...@tuxdriver.com;
> bl...@debian.org; ktray...@redhat.com; Ray Kinsella <m...@ashroe.eu>;
> dev@dpdk.org; Akhil Goyal <akhil.go...@nxp.com>; Yigit, Ferruh
> <ferruh.yi...@intel.com>; Ananyev, Konstantin
> <konstantin.anan...@intel.com>; dev@dpdk.org; Anoob Joseph
> <ano...@marvell.com>; Richardson, Bruce <bruce.richard...@intel.com>;
> Mcnamara, John <john.mcnam...@intel.com>; do...@seketeli.net; Andrew
> Rybchenko <arybche...@solarflare.com>; acon...@redhat.com; Trahe,
> Fiona <fiona.tr...@intel.com>
> Subject: Re: [dpdk-dev] [PATCH v2 4/4] add ABI checks
>
> 16/03/2020 13:57, Trahe, Fiona:
> > From: Kusztal, ArkadiuszX <arkadiuszx.kusz...@intel.com>
> > > > > > The patch we're working on will provide two versions of
> > > > > > rte_cryptodev_info_get(), both call the same PMD function from
> > > > > > the
> > > > dev_ops info_get fn ptr.
> > > > > > The default version operates s as normal, the 19.11 version
> > > > > > searches through the list returned by the PMD, looking for
> > > > > > sym.aead.algo = ChaChaPoly, it needs to strip it from
> > > > > the list.
> > > > > > As PMDs just pass a ptr to their capabilities list ( it isn't
> > > > > > a linked list, but an array with an end marker =
> > > > > > RTE_CRYPTODEV_END_OF_CAPABILITIES_LIST) if the API layer
> > > > > > detects Chacha it must allocate some space and store a local
> > > > > > copy of the trimmed
> > > > list. This must be stored only once per device.
> > >
> > > [Arek] The problem with this solution is that we need to allocate memory.
> > > So the question is how to handle unlikely case of malloc error when
> > > we operate inside void function rte_cryptodev_info_get?
> > > And even if we would pass somehow error condition to the caller then
> what to do is another question.
> >
> > [Fiona] Quick recap: To avoid breaking ABI, we must return a set of
> > capabilities with/without ChaChaPoly depending on the appl version. To
> > resolve this, within the rte_cryptodev layer, we propose to inspect the
> capabilities returned by PMD and strip ChaCha if it exists.
> > In that case memory for the new trimmed capabilities array has to be
> malloced by the lib.
>
> What happens if the capability is removed from the original capabilities
> input?
>
> > All good, except how to handle a malloc fail is yet another API breakage as
> rte_cryptodev_get_info() returns void.
> > We propose to return an empty capability list, i.e. a list with only
> > the END element (which can be done without malloc) in this corner case of
> a corner case.
> > Anyone see any issue with this?
>
> How can we use the feature if it is not advertised in capabilities?
What Fiona meant is that empty capability would indicate error condition in
this case. That's why she asked if you ok with this API breakage.
>
>
