From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id 114E547D1 for ; Tue, 6 Dec 2016 15:45:19 +0100 (CET) Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga101.fm.intel.com with ESMTP; 06 Dec 2016 06:45:19 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,310,1477983600"; d="scan'208";a="199605244" Received: from irsmsx102.ger.corp.intel.com ([163.33.3.155]) by fmsmga004.fm.intel.com with ESMTP; 06 Dec 2016 06:45:17 -0800 Received: from irsmsx156.ger.corp.intel.com (10.108.20.68) by IRSMSX102.ger.corp.intel.com (163.33.3.155) with Microsoft SMTP Server (TLS) id 14.3.248.2; Tue, 6 Dec 2016 14:45:17 +0000 Received: from irsmsx105.ger.corp.intel.com ([169.254.7.43]) by IRSMSX156.ger.corp.intel.com ([169.254.3.74]) with mapi id 14.03.0248.002; Tue, 6 Dec 2016 14:45:17 +0000 From: "Ananyev, Konstantin" To: "Richardson, Bruce" CC: =?iso-8859-1?Q?N=E9lio_Laranjeiro?= , "dev@dpdk.org" , Olivier Matz , "Lu, Wenzhuo" , Adrien Mazarguil Thread-Topic: [dpdk-dev] [PATCH] net: introduce big and little endian types Thread-Index: AQHSOpqjJZEmwRN0kU6+9TJvUFcv9KD4oKeAgADKCYCAAX/vkIAAD1IAgAALoxCAABAkgIAAD9eg Date: Tue, 6 Dec 2016 14:45:16 +0000 Message-ID: <2601191342CEEE43887BDE71AB9772583F0E47E1@irsmsx105.ger.corp.intel.com> References: <2601191342CEEE43887BDE71AB9772583F0E3F68@irsmsx105.ger.corp.intel.com> <20161205120603.GL21794@autoinstall.dev.6wind.com> <2601191342CEEE43887BDE71AB9772583F0E4632@irsmsx105.ger.corp.intel.com> <20161206115502.GA12224@bricha3-MOBL3.ger.corp.intel.com> <2601191342CEEE43887BDE71AB9772583F0E46DC@irsmsx105.ger.corp.intel.com> <20161206133427.GB15416@bricha3-MOBL3.ger.corp.intel.com> In-Reply-To: <20161206133427.GB15416@bricha3-MOBL3.ger.corp.intel.com> Accept-Language: en-IE, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.182] Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] [PATCH] net: introduce big and little endian types 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: Tue, 06 Dec 2016 14:45:20 -0000 >=20 > On Tue, Dec 06, 2016 at 12:41:00PM +0000, Ananyev, Konstantin wrote: > > > > > > > -----Original Message----- > > > From: Richardson, Bruce > > > Sent: Tuesday, December 6, 2016 11:55 AM > > > To: Ananyev, Konstantin > > > Cc: N=E9lio Laranjeiro ; dev@dpdk.org; Ol= ivier Matz ; Lu, Wenzhuo > > > ; Adrien Mazarguil > > > Subject: Re: [dpdk-dev] [PATCH] net: introduce big and little endian = types > > > > > > On Tue, Dec 06, 2016 at 11:23:42AM +0000, Ananyev, Konstantin wrote: > > > > Hi Neilo, > > > > > > > > > > > > Hi Neilo, > > > > > > > > > > > > > > This commit introduces new rte_{le,be}{16,32,64}_t types and = updates > > > > > > > rte_{le,be,cpu}_to_{le,be,cpu}_*() and network header structu= res > > > > > > > accordingly. > > > > > > > > > > > > > > Specific big/little endian types avoid uncertainty and conver= sion mistakes. > > > > > > > > > > > > > > No ABI change since these are simply typedefs to the original= types. > > > > > > > > > > > > It seems like quite a lot of changes... > > > > > > Could you probably explain what will be the benefit in return? > > > > > > Konstantin > > > > > > > > > > Hi Konstantin, > > > > > > > > > > The benefit is to provide documented byte ordering for data types > > > > > software is manipulating to determine when network to CPU (or CPU= to > > > > > network) conversion must be performed. > > > > > > > > Ok, but is it really worth it? > > > > User can still make a mistake and forget to call ntoh()/hton() at s= ome particular place. > > > > From other side most people do know that network protocols headers = are usually in BE format. > > > > I would understand the effort, if we'll have some sort of tool that= would do some sort of static code analysis > > > > based on these special types or so. > > > > Again, does it mean that we should go and change uint32_t to rte_le= _32 inside all Intel PMDs > > > > (and might be in some others too) to be consistent? > > > > Konstantin > > > > > > > > > > I actually quite like this patch as I think it will help make things > > > clear when the user is possibly doing something wrong. I don't think = we > > > need to globally change all PMDs to use the types, though. > > > > Ok, so where do you believe we should draw a line? > > Why let say inside lib/librte_net people should use these typedefs, but > > inside drivers/net/ixgbe they don't? >=20 > Because those are not public APIs. It would be great if driver writers > used the typedefs, but I don't think it should be mandatory. Ok, so only public API would have to use these typedefs when appropriate, c= orrect? I still think that the effort to make these changes and keep this rule outw= eighs the benefit, but ok if everyone else think it is useful - I wouldn't object too much.=20 >=20 > > > > > > > > One thing I'm wondering though, is if we might want to take this > > > further. For little endian environments, we could define the big endi= an > > > types as structs using typedefs, and similarly the le types on be > > > platforms, so that assigning from the non-native type to the native o= ne > > > without a transformation function would cause a compiler error. > > > > Not sure I understand you here. > > Could you possibly provide some example? > > > typedef struct { > short val; > } rte_be16_t; Hmm, so: uint32_t x =3D rte_be_to_cpu_32(1); would suddenly stop compiling? That definitely looks like an ABI breakage to me. Konstantin >=20 > That way if you try to assign a value of type rte_be16_t to a uint16_t > variable you'll get a compiler error, unless you use an appropriate > conversion function. In short, it changes things from not just looking > wrong - which is the main purpose of Neilo's patchset - to actually > making it incorrect from the compiler's point of view too. >=20 > /Bruce