diff options
authorThomas Petazzoni <>2013-12-05 19:11:10 (GMT)
committerPeter Korsgaard <>2013-12-08 21:38:13 (GMT)
commita4239f7fd1053c11bf4bb8bbc98cbe4b513f2d47 (patch)
parentedeb7d53978f20acc2306b71bc818e81298a68b3 (diff)
core: introduce the BR2_EXTERNAL variable
This commit introduces the BR2_EXTERNAL environment variable, which will allow to keep Buildroot customization (board-specific configuration files or root filesystem overlays, package and makefiles, as well as defconfigs) outside of the Buildroot tree. This commit only introduces the variable itself, and ensures that it is available within options. This allows us to use $BR2_EXTERNAL in a 'source' statement in Following patches extend the usage of BR2_EXTERNAL to other areas (packages and defconfigs). In details, this commit: * Introduces the BR2_EXTERNAL Kconfig option. This option has no prompt, and is therefore not visible to the user and also not stored in the .config file. It is automatically set to the value of the BR2_EXTERNAL environment variable. The only purpose of this BR2_EXTERNAL Kconfig option is to allow $BR2_EXTERNAL to be properly expanded when used inside Kconfig source statements. * Calculates the BR2_EXTERNAL value to use. If passed on the command line, then this value is taken in priority, and saved to a .br-external hidden file in the output directory. If not passed on the command line, then we read the .br-external file from the output directory. This allows the user to not pass the BR2_EXTERNAL value at each make invocation. If no BR2_EXTERNAL value is passed, we define it to support/dummy-external, so that the kconfig code finds an existing $(BR2_EXTERNAL)/package/ file to include. * Passes the BR2_EXTERNAL into the *config environment, so that its value is found when parsing/evaluating files and .config values. Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <> Signed-off-by: Thomas Petazzoni <> Reviewed-by: "Yann E. MORIN" <> Tested-by: "Yann E. MORIN" <> Acked-by: Ryan Barnett <> Tested-by: "Samuel Martin" <> Acked-by: "Samuel Martin" <> Signed-off-by: Peter Korsgaard <>
3 files changed, 32 insertions, 1 deletions
diff --git a/ b/
index 677fff6..ea060bc 100644
--- a/
+++ b/
@@ -14,6 +14,10 @@ config BR2_HOSTARCH
option env="HOSTARCH"
+config BR2_EXTERNAL
+ string
+ option env="BR2_EXTERNAL"
# Hidden boolean selected by pre-built packages for x86, when they
# need to run on x86-64 machines (example: pre-built external
# toolchains, binary tools like SAM-BA, etc.).
diff --git a/Makefile b/Makefile
index 6adacd9..f92fd9b 100644
--- a/Makefile
+++ b/Makefile
@@ -99,6 +99,29 @@ export CDPATH:=
BASE_DIR := $(shell mkdir -p $(O) && cd $(O) >/dev/null && pwd)
$(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.
+# On subsequent invocations of make, it is read in. It can still be overridden
+# on the command line, therefore the file is re-created every time make is run.
+# When BR2_EXTERNAL is not set, the .br-external file is removed and we point
+# to support/dummy-external. This makes sure we can unconditionally include the
+# and from the BR2_EXTERNAL directory. In this case,
+# override is necessary so the user can clear BR2_EXTERNAL from the command
+# line, but the dummy path is still used internally.
+BR2_EXTERNAL_FILE = $(BASE_DIR)/.br-external
+-include $(BR2_EXTERNAL_FILE)
+ifeq ($(BR2_EXTERNAL),)
+ override BR2_EXTERNAL = support/dummy-external
+ $(shell rm -f $(BR2_EXTERNAL_FILE))
+ $(shell echo BR2_EXTERNAL ?= $(BR2_EXTERNAL) > $(BR2_EXTERNAL_FILE))
@@ -631,7 +654,8 @@ COMMON_CONFIG_ENV = \
KCONFIG_AUTOCONFIG=$(BUILD_DIR)/buildroot-config/auto.conf \
KCONFIG_AUTOHEADER=$(BUILD_DIR)/buildroot-config/autoconf.h \
KCONFIG_TRISTATE=$(BUILD_DIR)/buildroot-config/tristate.config \
xconfig: $(BUILD_DIR)/buildroot-config/qconf outputmakefile
@mkdir -p $(BUILD_DIR)/buildroot-config
diff --git a/docs/manual/ b/docs/manual/
index f0bbff8..49421df 100644
--- a/docs/manual/
+++ b/docs/manual/
@@ -1,6 +1,9 @@
+# Packages included in BR2_EXTERNAL are not part of buildroot, so they
+# should not be included in the manual.
manual-update-lists: manual-check-dependencies-lists
$(Q)$(call MESSAGE,"Updating the manual lists...")
$(Q)BR2_DEFCONFIG="" TOPDIR=$(TOPDIR) O=$(O)/docs/manual/.build \
+ BR2_EXTERNAL=$(TOPDIR)/support/dummy-external \
python -B $(TOPDIR)/support/scripts/
# we can't use suitable-host-package here because that's not available in