Re: [dpdk-dev] [PATCH v4 1/4] ethdev: add the API for getting burst mode information

[Thomas Monjalon <thomas@monjalon.net>]

25/10/2019 18:02, Jerin Jacob:
> On Fri, Oct 25, 2019 at 9:15 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> > 25/10/2019 16:08, Ferruh Yigit:
> > > On 10/25/2019 10:36 AM, Thomas Monjalon wrote:
> > > > 15/10/2019 09:51, Haiyue Wang:
> > > >> Some PMDs have more than one RX/TX burst paths, add the ethdev API
> > > >> that allows an application to retrieve the mode information about
> > > >> Rx/Tx packet burst such as Scalar or Vector, and Vector technology
> > > >> like AVX2.
> > > >
> > > > I missed this patch. I and Andrew, maintainers of ethdev, were not CC'ed.
> > > > Ferruh, I would expect to be Cc'ed and/or get a notification before merging.
> > >
> > > It has been discussed in the mail list and went through multiple discussions,
> > > patch is out since the August, +1 to cc all maintainers I missed that part,
> > > but when the patch is reviewed and there is no objection, why block the merge?
> >
> > I'm not saying blocking the merge.
> > My bad is that I missed the patch and I am asking for help with a notification
> > in this case. Same for Andrew I guess.
> > Note: it is merged in master and I am looking to improve this feature.
> 
> > > >> +/**
> > > >> + * Ethernet device RX/TX queue packet burst mode information structure.
> > > >> + * Used to retrieve information about packet burst mode setting.
> > > >> + */
> > > >> +struct rte_eth_burst_mode {
> > > >> +  uint64_t options;
> > > >> +};
> > > >
> > > > Why a struct for an integer?
> > >
> > > Again by a request from me, to not need to break the API if we need to add more
> > > thing in the future.
> >
> > I would replace it with a string. This is the most flexible API.
> 
> IMO, Probably, best of both worlds make a good option here,
> as Haiyue suggested if we have an additional dev_specific[1] in structure.
> and when a pass to the application, let common code make final string as
> (options flags to string + dev_specific)
> 
> options flag can be zero if PMD does not have any generic flags nor
> interested in such a scheme.
> Generic flags will help at least to have some common code.
> 
> [1]
> struct rte_eth_burst_mode {
>         uint64_t options;
>         char dev_specific[128]; /* PMD has specific burst mode information */
> };

I really don't see how we can have generic flags.
The flags which are proposed are just matching
the functions implemented in Intel PMDs.
And this is a complicate solution.
Why not just returning a name for the selected Rx/Tx mode?