[RFC PATCH 08/12] build: use recursive addition for enabled drivers option

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

As with the libraries, recursively add dependencies of the enabled
drivers to the build list to enable building with, for example, just
--enable_drivers=net/mlx5 or --enable_drivers=net/cpfl.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
 drivers/meson.build | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/meson.build b/drivers/meson.build
index cb71bc8231..fe514a0b15 100644
--- a/drivers/meson.build
+++ b/drivers/meson.build
@@ -71,23 +71,26 @@ foreach driver_option : ['disable_drivers', 'enable_drivers']
 endforeach
 
 disable_drivers = run_command(list_dir_globs, disable_drivers, check: true).stdout().split()
-enable_drivers = run_command(list_dir_globs, enable_drivers, check: true).stdout().split()
-foreach d:enable_drivers
+requested_drivers = run_command(list_dir_globs, enable_drivers, check: true).stdout().split()
+foreach d:requested_drivers
     if disable_drivers.contains(d)
         error('Driver "@0@" is in both "enable_drivers" and "disable_drivers".'.format(d))
     endif
 endforeach
-require_drivers = true
-if enable_drivers.length() == 0
-    require_drivers = false
-    enable_drivers = run_command(list_dir_globs, '**', check: true).stdout().split()
-endif
+require_drivers = requested_drivers.length() != 0
 
 # these drivers must always be enabled, otherwise the build breaks
 always_enable = ['bus/pci', 'bus/vdev']
 # we always need a mempool driver, and ring is default, so make it mandatory
 always_enable += ['mempool/ring']
-enable_drivers += always_enable
+
+# expand the requested drivers to also include the drivers they depend on; with
+# no drivers requested every driver is wanted, so no list is needed
+enable_drivers = []
+if require_drivers
+    enable_drivers = run_command(resolve_deps_cmd, dpdk_deps_graph, '--drivers',
+            requested_drivers + always_enable, check: true).stdout().strip().split(',')
+endif
 
 default_cflags = machine_args
 default_cflags += ['-DALLOW_EXPERIMENTAL_API']
@@ -200,7 +203,7 @@ foreach subpath:subdirs
             name = name.split('/')[1]
         endif
 
-        if not enable_drivers.contains(drv_path)
+        if require_drivers and not enable_drivers.contains(drv_path)
             build = false
             reason = 'not in enabled drivers build config'
         elif disable_drivers.contains(drv_path)
-- 
2.53.0