core: introduce per br2-external NAME

This unique NAME is used to construct a per br2-external tree variable,
BR2_EXTERNAL_$(NAME)_PATH, which contains the path to the br2-external
tree.

This variable is available both from Kconfig (set in the Kconfig
snippet) and from the .mk files.

Also, display the NAME and its path as a comment in the menuconfig.

This will ultimately allow us to support multiple br2-external trees at
once, with that NAME (and thus BR2_EXTERNAL_$(NAME)) uniquely defining
which br2-external tree is being used.

The obvious outcome is that BR2_EXTERNAL should now no longer be used to
refer to the files in the br2-external tree; that location is now known
from the BR2_EXTERNAL_$(NAME)_PATH variable instead. This means we no
longer need to expose, and must stop from from exposing BR2_EXTERNAL as
a Kconfig variable.

Finally, this also fixes a latent bug in the pkg-generic infra, where we
would so far always refer to BR2_EXTERNAL (even if not set) to filter
the names of packages (to decide whether they are a bootloader, a
toolchain or a simple package).

Note: since the variables in the Makefile and in Kconfig are named the
same, the one we computed early on in the Makefile will be overridden by
the one in .config when we have it. Thus, even though they are set to
the same raw value, the one from .config is quoted and, being included
later in the Makefile, will take precedence, so we just re-include the
generated Makefile fragment a third time before includeing the
br2-external's Makefiles. That's unfortunate, but there is no easy way
around that as we do want the two variables to be named the same in
Makefile and Kconfig (and we can't ask the user to un-quote that variable
himself either), hence this little dirty triple-inclusion trick.

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>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

1 files changed, 14 insertions, 5 deletions

diff --git a/Makefile b/Makefile
index ff93caec1..e263b54b8 100644
--- a/Makefile
+++ b/Makefile
@@ -448,6 +448,14 @@ 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.
+include $(BR2_EXTERNAL_FILE)
+
 # Nothing to include if no BR2_EXTERNAL tree in use
 include $(BR2_EXTERNAL_MK)
 
@@ -763,7 +771,6 @@ COMMON_CONFIG_ENV = \
 	KCONFIG_AUTOHEADER=$(BUILD_DIR)/buildroot-config/autoconf.h \
 	KCONFIG_TRISTATE=$(BUILD_DIR)/buildroot-config/tristate.config \
 	BR2_CONFIG=$(BR2_CONFIG) \
-	BR2_EXTERNAL=$(BR2_EXTERNAL) \
 	HOST_GCC_VERSION="$(HOSTCC_VERSION)" \
 	BUILD_DIR=$(BUILD_DIR) \
 	SKIP_LEGACY=
@@ -842,7 +849,7 @@ define percent_defconfig
 	@$$(COMMON_CONFIG_ENV) BR2_DEFCONFIG=$(1)/configs/$$@ \
 		$$< --defconfig=$(1)/configs/$$@ $$(CONFIG_CONFIG_IN)
 endef
-$(eval $(foreach d,$(TOPDIR) $(BR2_EXTERNAL),$(call percent_defconfig,$(d))$(sep)))
+$(eval $(foreach d,$(TOPDIR) $(if $(BR2_EXTERNAL_NAME),$(BR2_EXTERNAL_$(BR2_EXTERNAL_NAME)_PATH)),$(call percent_defconfig,$(d))$(sep)))
 
 savedefconfig: $(BUILD_DIR)/buildroot-config/conf prepare-kconfig
 	@$(COMMON_CONFIG_ENV) $< \
@@ -969,12 +976,14 @@ list-defconfigs:
 	@echo 'Built-in configs:'
 	@$(foreach b, $(sort $(notdir $(wildcard $(TOPDIR)/configs/*_defconfig))), \
 	  printf "  %-35s - Build for %s\\n" $(b) $(b:_defconfig=);)
-ifneq ($(wildcard $(BR2_EXTERNAL)/configs/*_defconfig),)
+ifneq ($(BR2_EXTERNAL_NAME),)
+ifneq ($(wildcard $(BR2_EXTERNAL_$(BR2_EXTERNAL_NAME)_PATH)/configs/*_defconfig),)
 	@echo
 	@echo 'User-provided configs:'
-	@$(foreach b, $(sort $(notdir $(wildcard $(BR2_EXTERNAL)/configs/*_defconfig))), \
+	@$(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
 
 release: OUT = buildroot-$(BR2_VERSION)
@@ -994,7 +1003,7 @@ print-version:
 	@echo $(BR2_VERSION_FULL)
 
 include docs/manual/manual.mk
--include $(BR2_EXTERNAL)/docs/*/*.mk
+-include $(if $(BR2_EXTERNAL_NAME),$(BR2_EXTERNAL_$(BR2_EXTERNAL_NAME)_PATH)/docs/*/*.mk)
 
 .PHONY: $(noconfig_targets)