core: add support for multiple br2-external trees

Currently, we only support at most one br2-external tree. Being able
to use more than one br2-external tree can be very useful.

A use-case would be for having a br2-external to contain the basic
packages, basic board defconfigs and board files, provided by one team
responsible for the "board-bringup", while other teams consume that
br2-external as a base, and complements it each with their own set of
packages, defconfigs and extra board files.

Another use-case would be for third-parties to provide their own
Buildroot packaging in a br2-external tree, along-side the archives for
their stuff.

Finally, another use-case is to be able to add FLOSS packages in a
br2-external tree, and proprietary packages in another. This allows
to not touch the Buildroot tree at all, and still be able to get in
compliance by providing only that br2-external tree(s) that contains
FLOSS packages, leaving aside the br2-external tree(s) with the
proprietary bits.

What we do is to treat BR2_EXTERNAL as a colon-separated (space-
separated also work, and we use that internally) list of paths, on which
we iterate to construct:

  - the list of all br2-external names, BR2_EXTERNAL_NAMES,

  - the per-br2-external tree BR2_EXTERNAL_$(NAME) variables, which
    point each to the actual location of the corresponding tree,

  - the list of paths to all the external.mk files, BR2_EXTERNAL_MKS,

  - the space-separated list of absolute paths to the external trees,
    BR2_EXTERNAL_DIRS.

Once we have all those variables, we replace references to BR2_EXTERNAL
with either one of those.

This cascades into how we display the list of defconfigs, so that it is
easy to see what br2-external tree provides what defconfigs. As
suggested by Arnout, tweak the comment from "User-provided configs" to
"External configs", on the assumption that some br2-external trees could
be provided by vendors, so not necessarily user-provided. Ditto the menu
in Kconfig, changed from "User-provided options" to "External options".

Now, when more than one br2-external tree is used, each gets its own
sub-menu in the "User-provided options" menu. The sub-menu is labelled
with that br2-external tree's name and the sub-menu's first item is a
comment with the path to that br2-external tree.

If there's only one br2-external tree, then there is no sub-menu; there
is a single comment that contains the name and path to the br2-external
tree.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Romain Naour <romain.naour@openwide.fr>
Cc: Julien CORJON <corjon.j@ecagroup.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

1 files changed, 35 insertions, 22 deletions

diff --git a/Makefile b/Makefile
index e263b54b8..249cee85d 100644
--- a/Makefile
+++ b/Makefile
@@ -143,7 +143,7 @@ $(if $(BASE_DIR),, $(error output directory "$(O)" does not exist))
 # Handling of BR2_EXTERNAL.
 #
 # The value of BR2_EXTERNAL is stored in .br-external in the output directory.
-# The location of the external.mk makefile fragment is computed in that file.
+# The location of the external.mk makefile fragments is computed in that file.
 # On subsequent invocations of make, this file is read in. BR2_EXTERNAL can
 # still be overridden on the command line, therefore the file is re-created
 # every time make is run.
@@ -448,16 +448,15 @@ include boot/common.mk
 include linux/linux.mk
 include fs/common.mk
 
-# If using a br2-external tree, the BR2_EXTERNAL_$(NAME)_PATH variable
-# is also present in the .config file. Since .config is included after
-# we defined BR2_EXTERNAL_$(NAME)_PATH in the Makefile, the value in
-# that variable is quoted. We just include the generated Makefile fragment
-# .br2-external.mk a third time, which will set that variable to the
-# un-quoted value.
+# If using a br2-external tree, the BR2_EXTERNAL_$(NAME)_PATH variables
+# are also present in the .config file. Since .config is included after
+# we defined them in the Makefile, the values for those variables are
+# quoted. We just include the generated Makefile fragment .br2-external.mk
+# a third time, which will set those variables to the un-quoted values.
 include $(BR2_EXTERNAL_FILE)
 
 # Nothing to include if no BR2_EXTERNAL tree in use
-include $(BR2_EXTERNAL_MK)
+include $(BR2_EXTERNAL_MKS)
 
 # Now we are sure we have all the packages scanned and defined. We now
 # check for each package in the list of enabled packages, that all its
@@ -849,7 +848,7 @@ define percent_defconfig
 	@$$(COMMON_CONFIG_ENV) BR2_DEFCONFIG=$(1)/configs/$$@ \
 		$$< --defconfig=$(1)/configs/$$@ $$(CONFIG_CONFIG_IN)
 endef
-$(eval $(foreach d,$(TOPDIR) $(if $(BR2_EXTERNAL_NAME),$(BR2_EXTERNAL_$(BR2_EXTERNAL_NAME)_PATH)),$(call percent_defconfig,$(d))$(sep)))
+$(eval $(foreach d,$(TOPDIR) $(BR2_EXTERNAL_DIRS),$(call percent_defconfig,$(d))$(sep)))
 
 savedefconfig: $(BUILD_DIR)/buildroot-config/conf prepare-kconfig
 	@$(COMMON_CONFIG_ENV) $< \
@@ -972,19 +971,33 @@ help:
 	@echo 'it on-line at http://buildroot.org/docs.html'
 	@echo
 
+# List the defconfig files
+# $(1): base directory
+# $(2): br2-external name, empty for bundled
+define list-defconfigs
+	@first=true; \
+	for defconfig in $(1)/configs/*_defconfig; do \
+		[ -f "$${defconfig}" ] || continue; \
+		if $${first}; then \
+			if [ "$(2)" ]; then \
+				printf "External configs in $(2):\n"; \
+			else \
+				printf "Built-in configs:\n"; \
+			fi; \
+			first=false; \
+		fi; \
+		defconfig="$${defconfig##*/}"; \
+		printf "  %-35s - Build for %s\n" "$${defconfig}" "$${defconfig%_defconfig}"; \
+	done; \
+	$${first} || printf "\n"
+endef
+
+# We iterate over BR2_EXTERNAL_NAMES rather than BR2_EXTERNAL_DIRS,
+# because we want to display the name of the br2-external tree.
 list-defconfigs:
-	@echo 'Built-in configs:'
-	@$(foreach b, $(sort $(notdir $(wildcard $(TOPDIR)/configs/*_defconfig))), \
-	  printf "  %-35s - Build for %s\\n" $(b) $(b:_defconfig=);)
-ifneq ($(BR2_EXTERNAL_NAME),)
-ifneq ($(wildcard $(BR2_EXTERNAL_$(BR2_EXTERNAL_NAME)_PATH)/configs/*_defconfig),)
-	@echo
-	@echo 'User-provided configs:'
-	@$(foreach b, $(sort $(notdir $(wildcard $(BR2_EXTERNAL_$(BR2_EXTERNAL_NAME)_PATH)/configs/*_defconfig))), \
-	  printf "  %-35s - Build for %s\\n" $(b) $(b:_defconfig=);)
-endif
-endif
-	@echo
+	$(call list-defconfigs,$(TOPDIR))
+	$(foreach name,$(BR2_EXTERNAL_NAMES),\
+		$(call list-defconfigs,$(BR2_EXTERNAL_$(name)_PATH),$(name))$(sep))
 
 release: OUT = buildroot-$(BR2_VERSION)
 
@@ -1003,7 +1016,7 @@ print-version:
 	@echo $(BR2_VERSION_FULL)
 
 include docs/manual/manual.mk
--include $(if $(BR2_EXTERNAL_NAME),$(BR2_EXTERNAL_$(BR2_EXTERNAL_NAME)_PATH)/docs/*/*.mk)
+-include $(foreach dir,$(BR2_EXTERNAL_DIRS),$(dir)/docs/*/*.mk)
 
 .PHONY: $(noconfig_targets)