[v4,4/4] build: select optional libraries

  There is currently no way to know which libraries are optional.
Introduce a enable_libs option (close to what we have for drivers) so
that packagers or projects consuming DPDK can more easily select the
optional libraries that matter to them and disable other optional
libraries.

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
Changes since v3:
- split non related cleanup changes,
- fixed false positive complaints about disabling mandatory libs by
  building the list of always enabled libs, appending this list to
  enable_list and checking the disable side,
- updated enable/disable_libs descriptions,

Changes since v2:
- moved the IOVA check for kni build in lib/kni/meson.build,
- reworked deprecated libraries handling by only considering them when
  no enable_libs option is set. With this, no need for a default value
  in meson_options.txt, yet configurations in the CI must be adjusted,
- moved mandatory libraries check after enable/disable_libs evaluation,

---
 lib/meson.build   | 33 +++++++++++++++++++++++----------
 meson_options.txt |  4 +++-
 2 files changed, 26 insertions(+), 11 deletions(-)
  

On Wed, Jun 21, 2023 at 07:00:58PM +0200, David Marchand wrote:
> There is currently no way to know which libraries are optional.
> Introduce a enable_libs option (close to what we have for drivers) so
> that packagers or projects consuming DPDK can more easily select the
> optional libraries that matter to them and disable other optional
> libraries.
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---

LGTM - one minor suggestion inline below.

Acked-by: Bruce Richardson <bruce.richardson@intel.com>

> Changes since v3:
> - split non related cleanup changes,
> - fixed false positive complaints about disabling mandatory libs by
>   building the list of always enabled libs, appending this list to
>   enable_list and checking the disable side,
> - updated enable/disable_libs descriptions,
> 
> Changes since v2:
> - moved the IOVA check for kni build in lib/kni/meson.build,
> - reworked deprecated libraries handling by only considering them when
>   no enable_libs option is set. With this, no need for a default value
>   in meson_options.txt, yet configurations in the CI must be adjusted,
> - moved mandatory libraries check after enable/disable_libs evaluation,
> 
> ---
>  lib/meson.build   | 33 +++++++++++++++++++++++----------
>  meson_options.txt |  4 +++-
>  2 files changed, 26 insertions(+), 11 deletions(-)
> 
> diff --git a/lib/meson.build b/lib/meson.build
> index a6e9e19b42..407769b270 100644
> --- a/lib/meson.build
> +++ b/lib/meson.build
> @@ -92,17 +92,20 @@ dpdk_libs_deprecated += [
>          'kni',
>  ]
>  
> -disabled_libs = []
> -opt_disabled_libs = run_command(list_dir_globs, get_option('disable_libs'),
> -        check: true).stdout().split()
> -foreach l:opt_disabled_libs
> +disable_libs = run_command(list_dir_globs, get_option('disable_libs'), check: true).stdout().split()
> +
> +enable_libs = run_command(list_dir_globs, get_option('enable_libs'), check: true).stdout().split()
> +if enable_libs.length() == 0
> +    enable_libs += optional_libs
> +endif
> +
> +always_enable = []
> +foreach l:libraries
>      if not optional_libs.contains(l)
> -        warning('Cannot disable mandatory library "@0@"'.format(l))
> -        continue
> +        always_enable += l
>      endif
> -    disabled_libs += l
>  endforeach

Minor nit, I'd actually put this block further up the file just after the
optional_libs list. It's more an array definition, and moving it up puts
the next line (below) to add to enable_libs immediately after the other
assignments to enable_libs.

> -
> +enable_libs += always_enable
>  
>  default_cflags = machine_args
>  default_cflags += ['-DALLOW_EXPERIMENTAL_API']
> @@ -139,12 +142,22 @@ foreach l:libraries
>      if dpdk_libs_deprecated.contains(l) and not get_option('enable_deprecated_libs')
>          build = false
>          reason = 'deprecated libraries disabled via build config'
> -    elif disabled_libs.contains(l)
> +    elif not enable_libs.contains(l)
>          build = false
> -        reason = 'explicitly disabled via build config'
> +        reason = 'not in enabled libraries build config'
>          if dpdk_libs_deprecated.contains(l)
>              reason += ' (deprecated lib)'
>          endif
> +    elif disable_libs.contains(l)
> +        if always_enable.contains(l)
> +            warning('Cannot disable mandatory library "@0@"'.format(l))
> +        else
> +            build = false
> +            reason = 'explicitly disabled via build config'
> +            if dpdk_libs_deprecated.contains(l)
> +                reason += ' (deprecated lib)'
> +            endif
> +        endif
>      endif
>  
>      if build
> diff --git a/meson_options.txt b/meson_options.txt
> index f959015e46..9951563146 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -11,7 +11,7 @@ option('disable_apps', type: 'string', value: '', description:
>  option('disable_drivers', type: 'string', value: '', description:
>         'Comma-separated list of drivers to explicitly disable.')
>  option('disable_libs', type: 'string', value: '', description:
> -       'Comma-separated list of libraries to explicitly disable. [NOTE: not all libs can be disabled]')
> +       'Comma-separated list of optional libraries to explicitly disable. [NOTE: mandatory libs cannot be disabled]')
>  option('drivers_install_subdir', type: 'string', value: 'dpdk/pmds-<VERSION>', description:
>         'Subdirectory of libdir where to install PMDs. Defaults to using a versioned subdirectory.')
>  option('enable_docs', type: 'boolean', value: false, description:
> @@ -26,6 +26,8 @@ option('enable_driver_sdk', type: 'boolean', value: false, description:
>         'Install headers to build drivers.')
>  option('enable_kmods', type: 'boolean', value: false, description:
>         'build kernel modules')
> +option('enable_libs', type: 'string', value: '', description:
> +       'Comma-separated list of optional libraries to explicitly enable. [NOTE: mandatory libs are always enabled]')
>  option('examples', type: 'string', value: '', description:
>         'Comma-separated list of examples to build by default')
>  option('ibverbs_link', type: 'combo', choices : ['static', 'shared', 'dlopen'], value: 'shared', description:
> -- 
> 2.40.1
>