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[204.195.22.127]) by smtp.gmail.com with ESMTPSA id l22sm2979307pjy.31.2020.08.04.09.20.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Aug 2020 09:20:15 -0700 (PDT) Date: Tue, 4 Aug 2020 09:20:07 -0700 From: Stephen Hemminger To: Bruce Richardson Cc: pbhagavatula@marvell.com, jerinj@marvell.com, Ray Kinsella , Neil Horman , John McNamara , Marko Kovacevic , dev@dpdk.org, thomas@monjalon.net, david.marchand@redhat.com Message-ID: <20200804092007.54bf76f3@hermes.lan> In-Reply-To: <20200804104153.GA1464@bricha3-MOBL.ger.corp.intel.com> References: <20200802105137.1666-1-pbhagavatula@marvell.com> <20200803072903.1209-1-pbhagavatula@marvell.com> <20200804104153.GA1464@bricha3-MOBL.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH v2] doc: add reserve fields to eventdev public structures X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Tue, 4 Aug 2020 11:41:53 +0100 Bruce Richardson wrote: > On Mon, Aug 03, 2020 at 12:59:03PM +0530, pbhagavatula@marvell.com wrote: > > From: Pavan Nikhilesh > > > > Add 64 byte padding at the end of event device public structure to allow > > future extensions. > > > > Signed-off-by: Pavan Nikhilesh > > Acked-by: Jerin Jacob > > --- > > v2 Changes: > > - Modify commit title. > > - Add patch reference to doc. > > > > doc/guides/rel_notes/deprecation.rst | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst > > index ea4cfa7a4..ec5db68e9 100644 > > --- a/doc/guides/rel_notes/deprecation.rst > > +++ b/doc/guides/rel_notes/deprecation.rst > > @@ -151,3 +151,14 @@ Deprecation Notices > > Python 2 support will be completely removed in 20.11. > > In 20.08, explicit deprecation warnings will be displayed when running > > scripts with Python 2. > > + > > +* eventdev: A 64 byte padding is added at the end of the following structures > > + in event device library to support future extensions: > > + ``rte_event_crypto_adapter_conf``, ``rte_event_eth_rx_adapter_conf``, > > + ``rte_event_eth_rx_adapter_queue_conf``, ``rte_event_eth_tx_adapter_conf``, > > + ``rte_event_timer_adapter_conf``, ``rte_event_timer_adapter_info``, > > + ``rte_event_dev_info``, ``rte_event_dev_config``, ``rte_event_queue_conf``, > > + ``rte_event_port_conf``, ``rte_event_timer_adapter``, > > + ``rte_event_timer_adapter_data``. > > + Reference: > > + http://patches.dpdk.org/project/dpdk/list/?series=10728&archive=both&state=* > > -- > > I don't like this idea of adding lots of padding to the ends of these > structures. For some structures, such as the public arrays for devices it > may be necessary, but for all the conf structures passed as parameters to > functions I think we can do better. Since these structures are passed by > the user to various functions, function versioning can be used to ensure > that the correct function in eventdev is always called. From there to the > individual PMDs, we can implement ABI compatibility by either: > 1. including the length of the struct as a parameter to the driver. (This is > a bit similar to my proposal for rawdev [1]) > 2. including the ABI version as a parameter to the driver. > > Regards > /Bruce > > [1] http://inbox.dpdk.org/dev/?q=enhance+rawdev+APIs This is a bad idea. Reserved fields won't work because nothing requires that the application zero them. You can't start using them later because the application may put uninitialized or junk data there.