Re: [dpdk-dev] [PATCH 1/1] build: allow disabling libs

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, Sep 18, 2020 at 02:54:21PM +0200, Mohammed Hawari wrote:
> Hello Bruce,
> 
> Thanks for the quick response, see inline
> 
> Best regards,
> 
> Mohammed
> 
> > On 18 Sep 2020, at 13:43, Bruce Richardson <bruce.richardson@intel.com> wrote:
> > 
> > On Fri, Sep 18, 2020 at 10:49:23AM +0200, Mohammed Hawari wrote:
> >> Similarly to the disable_drivers option, the disable_libs option is
> >> introduced. This allows to selectively disable the build of elements
> >> in libs to speed-up the build process.
> >> 
> >> Signed-off-by: Mohammed Hawari <mohammed@hawari.fr>
> >> ---
> > 
> > While I don't particularly like allowing libs to be enabled and disabled
> > since it complicates the build, I can see why it's necessary. This is an
> > area that does need some discussion, as I believe others have some opinions
> > in this area too.
> > 
> > However, for now, some additional thoughts, both on this patch and in
> > general:
> > 
> > 1. I see you included disabling apps if their required libs are not
> >   available. What about the drivers though?
> To my understanding, in the current code, the drivers/meson.build file already
> does that check with:
> 
> foreach d:deps
>                 if not is_variable('shared_rte_' + d)
>                     build = false
> 

Yes, my mistake, I forgot that that was added as one driver could depend
upon another. :-(

> > 2. A bigger issue is whether this is really what we want to do, guarantee a
> >   passing build even if vast chunks of DPDK are actually enabled? I'd tend
> >   towards "no" in this case, and I'd rather see disabling of libs more
> >   constrained.
> > 3. To this end, I think I'd rather see us maintain a set of libs which are
> >   allowed to be disabled, and prevent the rest from being so. For example,
> >   it makes no sense in DPDK to disable the EAL or mempool libs, since nothing
> >   will build, while the bitrate_stats or latency_stats libs could likely
> >   be disabled with little or no impact.
> I tend to agree with that more structured approach, but I am going to wait until
> we get some more thoughts from the community before starting that work.
> 

That seems a wise approach. If there is no consensus after a while here, it
probably needs to go to the technical board.