> 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. 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. Regards, Keith
