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 Config.in 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 Config.in options. This allows us to use
$BR2_EXTERNAL in a 'source' statement in Config.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/Config.in file to
include.
* Passes the BR2_EXTERNAL into the *config environment, so that its
value is found when parsing/evaluating Config.in files and .config
values.
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: Ryan Barnett <rjbarnet@rockwellcollins.com>
Tested-by: "Samuel Martin" <s.martin49@gmail.com>
Acked-by: "Samuel Martin" <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
diff --git a/Makefile b/Makefile
index 6adacd9..f92fd9b 100644
--- a/Makefile
+++ b/Makefile
@@ -99,6 +99,29 @@
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
+# Config.in and external.mk 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))
+else
+ $(shell echo BR2_EXTERNAL ?= $(BR2_EXTERNAL) > $(BR2_EXTERNAL_FILE))
+endif
+
+
BUILD_DIR:=$(BASE_DIR)/build
STAMP_DIR:=$(BASE_DIR)/stamps
BINARIES_DIR:=$(BASE_DIR)/images
@@ -631,7 +654,8 @@
KCONFIG_AUTOCONFIG=$(BUILD_DIR)/buildroot-config/auto.conf \
KCONFIG_AUTOHEADER=$(BUILD_DIR)/buildroot-config/autoconf.h \
KCONFIG_TRISTATE=$(BUILD_DIR)/buildroot-config/tristate.config \
- BUILDROOT_CONFIG=$(BUILDROOT_CONFIG)
+ BUILDROOT_CONFIG=$(BUILDROOT_CONFIG) \
+ BR2_EXTERNAL=$(BR2_EXTERNAL)
xconfig: $(BUILD_DIR)/buildroot-config/qconf outputmakefile
@mkdir -p $(BUILD_DIR)/buildroot-config