From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id 5405311A4 for ; Fri, 16 Nov 2018 15:19:42 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Nov 2018 06:19:41 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,240,1539673200"; d="scan'208";a="100825519" Received: from fmsmsx108.amr.corp.intel.com ([10.18.124.206]) by orsmga003.jf.intel.com with ESMTP; 16 Nov 2018 06:19:41 -0800 Received: from fmsmsx118.amr.corp.intel.com ([169.254.1.160]) by FMSMSX108.amr.corp.intel.com ([169.254.9.157]) with mapi id 14.03.0415.000; Fri, 16 Nov 2018 06:19:40 -0800 From: "Wiles, Keith" To: "Ananyev, Konstantin" CC: Thomas Monjalon , Ilya Maximets , "dev@dpdk.org" , "Yigit, Ferruh" , "ovs-dev@openvswitch.org" , "Stokes, Ian" , "Kevin Traynor" , Ophir Munk , "Shahaf Shuler" , Eelco Chaudron , "arybchenko@solarflare.com" Thread-Topic: [dpdk-dev] Direct using of 'rte_eth_devices' in DPDK apps. Thread-Index: AQHUfZH8wsAJ6vVrrUmombz8AJ2tkaVS+cmA Date: Fri, 16 Nov 2018 14:19:40 +0000 Message-ID: <037382C8-F699-4327-B7D0-B385AA8A0EFE@intel.com> References: <70d58383-da8b-4c15-a8c4-f6f853268486@samsung.com> <11426330.8DnILqFDIn@xps> <2601191342CEEE43887BDE71AB977258010CEB8C73@IRSMSX106.ger.corp.intel.com> In-Reply-To: <2601191342CEEE43887BDE71AB977258010CEB8C73@IRSMSX106.ger.corp.intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.254.99.227] Content-Type: text/plain; charset="us-ascii" Content-ID: <466DCBFB196693469CD61008790612C3@intel.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] Direct using of 'rte_eth_devices' in DPDK apps. 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: , X-List-Received-Date: Fri, 16 Nov 2018 14:19:42 -0000 > On Nov 16, 2018, at 3:51 AM, Ananyev, Konstantin wrote: >=20 > Hi everyone, >=20 >>=20 >> Hi, >>=20 >> 16/11/2018 09:42, Ilya Maximets: >>> Hi, >>> While discussing the ways to enable DPDK 18.11 new features in OVS >>> there was suggestions to use 'rte_eth_devices[]' array directly. >>> But this array is marked as '@internal' and also it located in >>> the internal header 'lib/librte_ethdev/rte_ethdev_core.h' with the >>> following disclaimer: >>>=20 >>> /** >>> * @file >>> * >>> * RTE Ethernet Device internal header. >>> * >>> * This header contains internal data types. But they are still part of = the >>> * public API because they are used by inline functions in the published= API. >>> * >>> * Applications should not use these directly. >>> * >>> */ >>>=20 >>> From the other hand, test-pmd and some example apps in DPDK source >>> tree are using this array for various reasons. >>>=20 >>> So, is it OK to use this array directly or not? >>=20 >> Good question :) >> Thanks for bringing this discussion. >>=20 >> As you said, it is public because of inline functions using it directly >> for performance purpose. The DPDK API is bad for separating public and >> internal stuff. And over time, there is not a lot of attention on trying >> to not use internal symbols in applications. >>=20 >>> In general we need to change the API, i.e. make 'rte_eth_devices' part >>> of a public API. Or change the test-pmd and example apps to stop >>> using it. >>=20 >> I agree we need to decide an option and make it clear. >>=20 >> We can try to make this variable private and add more public functions >> to use it (I'm thinking at more iterators like sibling ones). >> It would clarify the API. >> It can be evaluated what is the real cost after compiler optimization >> for Rx/Tx functions. It can also be evaluated to uninline functions. >>=20 >> On the other hand, we can wonder what is the real benefit of trying to >> hide access to internal resources. Should we make all public? >=20 > In that case every change in any of such structures will be an ABI breaka= ge. > Even now any change in rte_eth_dev is quite problematic because of that. > I think we better keep them private as much as possible and cleanup > our examples and testpmd code. > Konstantin I Agree here, I have noticed a few places we allow direct access to interna= l data structures, which we need to restrict access by making them private = with getter/setter functions or just getter/setter functions even if we can= not make them private. At least with moving members and adding members we = can state that it is not a ABI breakage as long as everyone uses the getter= /setter functions. These functions could not be inline functions correct as= that would still break API? >=20 >>=20 >>> One more related question: Is it OK to access internal device >>> stuff using 'device' pointer obtained by 'rte_eth_dev_info'? >>> This looks really dangerous. It's unclear why pointers like this >>> exposed to user. >>=20 >> It's a lot easier to expose pointers than doing a good API for all uses. >> We need to question what is really dangerous and what we want to avoid? Regards, Keith