> -----Original Message----- > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Morten Brørup > Sent: Wednesday, July 12, 2017 3:25 PM > To: Wiles, Keith <keith.wi...@intel.com> > Cc: Thomas Monjalon <tho...@monjalon.net>; DPDK <dev@dpdk.org>; Olivier > Matz <olivier.m...@6wind.com>; Wang, Zhihong <zhihong.w...@intel.com>; > Yuanhan Liu <yuanhan....@linux.intel.com>; Ananyev, Konstantin > <konstantin.anan...@intel.com>; Richardson, Bruce > <bruce.richard...@intel.com>; Chilikin, Andrey <andrey.chili...@intel.com>; > Jan Blunck <jblu...@infradead.org>; Nélio Laranjeiro > <nelio.laranje...@6wind.com>; arybche...@solarflare.com; > jerin.ja...@caviumnetworks.com > Subject: Re: [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and > nbsegments > > > -----Original Message----- > > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Wiles, Keith > > Sent: Tuesday, July 11, 2017 6:48 PM > > To: Morten Brørup > > Cc: Thomas Monjalon; DPDK; Olivier Matz; Wang, Zhihong; Yuanhan Liu; > > Ananyev, Konstantin; Richardson, Bruce; Chilikin, Andrey; Jan Blunck; > > Nélio Laranjeiro; arybche...@solarflare.com; > > jerin.ja...@caviumnetworks.com > > Subject: Re: [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and > > nbsegments > > > > > > > On Jul 11, 2017, at 10:23 AM, Morten Brørup > > <m...@smartsharesystems.com> wrote: > > > > > >> -----Original Message----- > > >> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Thomas > > >> Monjalon > > >> Sent: Tuesday, July 11, 2017 5:06 PM > > >> To: Morten Brørup > > >> Cc: dev@dpdk.org; Wiles, Keith; Olivier Matz; Wang, Zhihong; > > >> Yuanhan Liu; Ananyev, Konstantin; Richardson, Bruce; Chilikin, > > >> Andrey; Jan Blunck; nelio.laranje...@6wind.com; > > >> arybche...@solarflare.com; jerin.ja...@caviumnetworks.com > > >> Subject: Re: [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port > > and > > >> nbsegments > > >> > > >> 11/07/2017 15:30, Morten Brørup: > > >>> Morten Brørup wrote: > > >>>> Olivier Matz wrote: > > >>>>> As I said in a previous message, I think a good first step would > > >>>>> be to introduce a typedef for the port number: > > >> rte_eth_port_num_t. > > >>>>> It can still be uint8_t for now, and can be switched to 16 bits > > >> in > > >>>>> one step when everyone uses this new type. > > >>>> > > >>>> I think that DPDK follows the Linux tradition of exposing the > > >>>> variable types, as opposed to hiding them behind typedefs. This > > has > > >>>> the unfortunate consequence that when a variable type changes, it > > >>>> has to be changed everywhere. > > >>>> > > >>>> Introducing a rte_eth_port_num_t will require changing the same > > >>>> files at the same locations everywhere, so not even as a > > >>>> temporary solution will it be beneficial. > > >> [...] > > >>> What I was trying to communicate with my long argument about type > > >> definitions was: When the type changed from 8 bit to 16 bit, the > > type > > >> needs to change from uint8_t to uint16_t everywhere too, including > > in > > >> the ethdev APIs. > > >>> > > >>> Don't start breaking coding conventions here by hiding the type of > > >> this variable. > > >> > > >> So, Morten, you are against the typedef, right? > > >> Because we need to change it everywhere anyway, right? > > >> > > >> Note: I have no strong opinion. > > > > > > I'm against the typedef because it would break convention, and I'm a > > strong proponent of conventions. In other projects, I'm all for > > typedefs, virtual classes, inheritance etc., but DPDK follows the > > Linux convention of not hiding simple types. > > > > > > We need to change it from uint8_t everywhere, regardless what we > > > change it to. (But if we need to change it again sometime in the > > > future, then a typedef will save us next time.) > > > > If the number of ports go beyond 64K then I will be the first one (if > > still alive) to eat this email. :-) The only reason to have more then > > 2 bytes would be to encode something into the port id value, which I > > could see, but a very slim chance IMHO. > > > > > > > > However, if we change the convention and start hiding simple types, > > they still need the rte_ prefix regardless if they are popular or > > obscure types. Even struct rte_mbuf has the rte_ prefix, and I > > consider that a very popular type. If so, rte_port_t would be a good > > name for this type. > > > > > > My preference: Follow convention and change it to uint16_t > > everywhere. > > > > > > Med venlig hilsen / kind regards > > > - Morten Brørup > > > > > > > As we must change the uint8_t to uint16_t, then I would like it to be > > more descriptive via a typedef. I really do not see us needing to > > change it again in the near future. The only reason to make it a > > typedef is to be able to identify from just the prototype of the > > function that it takes a port ID value, which I am in favor of doing > > here for that reason. > > That is not a very good reason: When used as a function parameter, the type is > only shown in the function declaration, whereas the variable name is shown > every time it is used inside the function. So remember to always use > meaningful > variable names, such as "port" (like in the mbuf structure) or "port_id" > (used in > other places). > > > > > As for Olivier’s statement about the typedef name I do not see the > > need for ‘_eth_' to be part of the typedef as it conveys no extra > > information in the name. Everything port related in DPDK is a ethernet > > type device or port. If we do add something like fiber channel maybe > > rte_pid_t is reason to that too, but if it contains ‘_eth_’ it would > > not. > > > > I would like to see names that are just short enough to convey the > > information and not be redundant. IMHO rte_pid_t is fine, but if we > > use some something similar to the length of uint8_t (7) or uint16_t > > (8) characters then we would not have to also reformat the line more > > then needed. Using rte_pid_t (pid == port_id) we only extend the > > length by one (or two) characters and most likely the added byte(s) > > will not cause more format problems in the code. > > I still don't support typedefs for scalar types. I consider it against the > coding > style, although after reviewing the official DPDK Coding Style documentation > (http://dpdk.org/doc/guides/contributing/coding_style.html), I can see that > it is > not explicitly stated. Please also note that section 1.5.7 of the DPDK Coding > Style documentation says that the _t postfix should be avoided. Anyway, if we > end up with a typedef, please don't use something resembling pid_t known from > POSIX (https://www.gnu.org/software/libc/manual/html_node/Process- > Identification.html). >
How about rte_dev_id_t? Thanks Zhiyong > > > > > Regards, > > Keith
