[PATCH v4 3/4] build: select deprecated libraries

[Bruce Richardson]

On Fri, Jun 23, 2023 at 11:35:29AM +0200, David Marchand wrote:
> Hello Bruce,
> 
> On Thu, Jun 22, 2023 at 10:43 AM Bruce Richardson
> <bruce.richardson at intel.com> wrote:
> >
> > On Wed, Jun 21, 2023 at 07:00:57PM +0200, David Marchand wrote:
> > > Rework deprecated libraries selection by introducing a new configuration
> > > option.
> > >
> > > This breaks existing configurations that were relying on disable_libs=''
> > > for enabling deprecated libraries.
> > > On the other hand, it will make enabling optional libraries more
> > > straightforward by taking the deprecated libraries out of the picture.
> > >
> > > Signed-off-by: David Marchand <david.marchand at redhat.com>
> >
> > This gives us a single on/off value for the deprecated libs. So if you
> > wants to build only a single deprecated lib, you need to turn on this
> > option and then use "disable_libs/enable_libs" option to then selectively
> > pick which of the deprecated libs you actually want. Is that the expected
> > behaviour? Just checking that we don't want this to be a list too.
> 
> Yes, I wanted a single unified filtering stage.
> 
> But I think your suggestion is easier to use.

Slightly easier for the simple case.

> 
> - That would make it simpler for people who simply want to enable kni,
> as you mentionned before:
> $ meson setup plop -Denable_deprecated_libs=kni
> 
> But I would make this list not overlap with the disable/enable_libs
> options evaluation.
> Otherwise, in the case of a enable_libs user, the user would have to
> set kni in both lists, which is not that great:
> $ meson setup plop -Denable_deprecated_libs=kni -Denable_libs=kni,vhost
> 
> Instead, I would make it so the config is done as:
> $ meson setup plop -Denable_deprecated_libs=kni -Denable_libs=vhost
> 
> Is this what you had in mind?
> 
I'm not sure myself what I had in mind, just asking if it had been
considered as much as anything else.

Having them not-overlap would seem to be necessary to provide a meaningful
interface.

> 
> - I don't have a usage for this, but if we go with separating
> deprecated and "normal" optional libs filtering, should I introduce a
> disable_deprecated_libs too?
>

That would give us *way* to many options. I think for the sake of simplicity
we probably are as well to just go with what you are proposing in this set.
Since we only have two deprecated libraries - and hopefully never many more - 
the benefit of the list for that setting is probably minimal. I'm keen to
avoid too much complexity if we can manage it.