package/dpdk: make drivers selectable

Add BR2_PACKAGE_DPDK_DRIVERS_LIST to control which DPDK applications are
built:
  - empty : use DPDK defaults
  - none  : disable all drivers (-Ddisable_drivers='*/*')
  - list  : pass to -Denable_drivers= (comma-separated)

Signed-off-by: Maxime Leroy <maxime@leroys.fr>
[Julien: slightly change the drivers Config.in help text:
 - rename net/ixgbe to net/intel/ixgbe
 - change find -maxdepth value to 3
]
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/dpdk/Config.in

@@ -43,6 +43,27 @@ config BR2_PACKAGE_DPDK_EXAMPLES
 config BR2_PACKAGE_DPDK_TESTS
 	bool "Install tests"
 
+config BR2_PACKAGE_DPDK_DRIVERS_LIST
+	string "List of enabled drivers"
+	help
+	  Controls which DPDK drivers are built.
+
+	  Values:
+	   (empty): use DPDK defaults
+	   none   : build no drivers
+	   list   : e.g. "net/virtio,net/intel/ixgbe"
+
+	  To list possible drivers found in the DPDK source tree:
+	    find drivers -mindepth 2 -maxdepth 3 -type d \
+	    ! -printf '%P\n' | sort
+
+	  Note: providing manually a list of dpdk drivers to enable
+	  does not automatically enable its dependencies (internal or
+	  external). It is the user responsiblity to add internal dpdk
+	  dependencies in this list, and/or select the relevant
+	  Buildroot packages for external dependencies. DPDK
+	  configuration will fail in case of missing dependencies.
+
 endif
 
 comment "dpdk needs a glibc toolchain w/ threads, gcc >= 4.9, headers >= 4.19"

package/dpdk/dpdk.mk

@@ -47,6 +47,15 @@ else
 DPDK_CONF_OPTS += -Dexamples=
 endif
 
+DPDK_DRIVERS := $(call qstrip,$(BR2_PACKAGE_DPDK_DRIVERS_LIST))
+ifneq ($(DPDK_DRIVERS),)
+  ifeq ($(DPDK_DRIVERS),none)
+    DPDK_CONF_OPTS += -Ddisable_drivers='*/*'
+  else
+    DPDK_CONF_OPTS += -Denable_drivers='$(DPDK_DRIVERS)'
+  endif
+endif
+
 ifeq ($(BR2_PACKAGE_DPDK_TESTS),y)
 DPDK_CONF_OPTS += -Dtests=true
 else