Re: [dpdk-dev] [PATCH v2 0/7] Removal of PCI bus ABIs

["Xia, Chenbo" <chenbo.xia@intel.com>]

> -----Original Message-----
> From: Thomas Monjalon <thomas@monjalon.net>
> Sent: Thursday, October 14, 2021 4:26 PM
> To: Harris, James R <james.r.harris@intel.com>; Walker, Benjamin
> <benjamin.walker@intel.com>; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: Liu, Changpeng <changpeng.liu@intel.com>; David Marchand
> <david.marchand@redhat.com>; dev@dpdk.org; Aaron Conole <aconole@redhat.com>;
> Zawadzki, Tomasz <tomasz.zawadzki@intel.com>
> Subject: Re: [dpdk-dev] [PATCH v2 0/7] Removal of PCI bus ABIs
> 
> 14/10/2021 10:07, Xia, Chenbo:
> > From: Thomas Monjalon <thomas@monjalon.net>
> > > 14/10/2021 09:00, Xia, Chenbo:
> > > > From: Thomas Monjalon <thomas@monjalon.net>
> > > > > 14/10/2021 04:21, Xia, Chenbo:
> > > > > > From: Thomas Monjalon <thomas@monjalon.net>
> > > > > > > Yes I think we need to agree on functions to keep as-is for
> > > compatibility.
> > > > > > > Waiting for your input please.
> > > > > >
> > > > > > So, do you mean currently DPDK doesn't guarantee ABI for drivers
> > > > >
> > > > > Yes
> > > > >
> > > > > > but could have driver ABI in the future?
> > > > >
> > > > > I don't think so, not general compatibility,
> > > > > but we can think about a way to avoid breaking SPDK specifically,
> > > > > which has less requirements.
> > > >
> > > > So the problem here is exposing some APIs to SPDK directly? Without the
> > > 'enable_driver_sdk'
> > > > option, I don't see a solution of both exposed and not-ABI. Any idea in
> your
> > > mind?
> > >
> > > No the idea is to keep using enable_driver_sdk.
> > > But so far, there is no compatibility guarantee for driver SDK.
> > > The discussion is about which basic compatibility requirement is needed
> for
> > > SPDK.
> >
> > Sorry for not understanding your point quickly, but what's the difference of
> > 'general compatibility' and 'basic compatibility'? Because in my mind, one
> > struct or function should either be ABI-compatible or not. Could you help
> explain
> > it a bit?
> 
> I wonder whether we could have a guarantee for a subset of structs and
> functions.
> Anyway, this is just opening the discussion to collect some inputs first.
> Then we'll have to check what is possible and get a techboard approval.
> 

After going through related code in SPDK, I think we can add some new functions and keep
some macros in the exposed header (i.e., rte_bus_pci.h) for SPDK to register pci driver
and get needed info.

Most structs/marocs will be hided and SPDK can use the new proposed APIs and small set
of macros/structs to build. In this way, the problem of SPDK building with DPDK distros
and ABI issue can both be solved. APIs like struct rte_pci_device and struct rte_pci_driver
can be hided to minimize pci bus ABI.

Thomas & SPDK folks, please share your opinions of above.

Thanks,
Chenbo