On Wed, Jul 12, 2017 at 06:23:38PM +0200, Thomas Monjalon wrote: > 12/07/2017 17:57, Morten Brørup: > > From: Stephen Hemminger > > > Morten Brørup <m...@smartsharesystems.com> wrote: > > > > From: Yang, Zhiyong [mailto:zhiyong.y...@intel.com] > > > > > From: Morten Brørup > > > > > > From: Wiles, Keith > > > > > > > > On Jul 11, 2017, at 10:23 AM, Morten Brørup wrote: > > > > > > > > From: Thomas Monjalon > > > > > > > >> 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. > > > > > > > > > > > > > > > My preference: Follow convention and change it to uint16_t > > > > > > > > everywhere. > > > > > > > > > > > > > > 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). > > > > > > > > > > > > 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? > > > > > > > > If the DPDK Coding Style is based on Linux Coding Style, we should > > > > avoid typedefs in general, not just for structures. Please read Linus > > > > Torvalds' opinions about it: > > > > http://yarchive.net/comp/linux/typedefs.html > > > > > > > > Perhaps the DPDK Coding Style should be updated to clarify this. (Or > > > > if we decide otherwise, to explicitly mention this deviation from the > > > > Linux coding style.) > > > > > > It is logical to use typedef's for this kind of scalar type that may > > > need to change. > > > Names matter, please avoid pid (confuse with posix) and dev (confuse > > > with device id). > > > I would prefer: rte_portid_t and rte_queueid_t > > > > > > Longer term, probably rte_eth_devices[] needs to go. Change port id > > > into something more like ifindex. And use sparse data structure to > > > allow very large number of devices and non-contiguous lookup. Think of > > > a VPN server where each VPN connection looks like a DPDK device. > > > > We are using a non-contiguous ifindex in our firmware, for virtual > > interfaces as you mention, so I get your point here! > > But until DPDK gets there, I suppose the DPDK port id is considered > > more or less contiguous. > > > > You clearly have a longer track record working with Linus than me, > > so if you interpret the coding style like that, I will not object > > anymore - as my objection was based on coding style. And will someone > > please update the DPDK Coding Style document accordingly... > > > > rte_portid_t is fine with me, but why not just rte_port_t? > > One problem with opaque typedef is that we don't know how to print them, > except if we have a PRIx macro. > > So I suggest to keep with uint16_t (my preference), > or to add a printf format macro.
+1 for using basic types rather than typedefs.
