[Buildroot] [PATCHv2 1/4] core: introduce the BR2_EXTERNAL variable

[Arnout Vandecappelle <arnout@mind.be>]

On 14/09/13 21:03, Thomas Petazzoni wrote:
> 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, so that string options used to
> specify paths to directories or files can use $BR2_EXTERNAL as a

  $(BR2_EXTERNAL). The $ is expanded by make. Same comment applies to 
other places in the commit message as well. You did put it correctly in 
the manual.

> reference. For example, one can use
> $BR2_EXTERNAL/board/<someboard>/kernel.config as the
> BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE value.
>
> 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 option values.
>
>   * Ensures that the path given in BR2_EXTERNAL is an absolute path, or
>     if not path is given, ensures that BR2_EXTERNAL points to a dummy
>     implementation in $(TOPDIR)/support/dummy-external/. This last part
>     is not directly useful in this commit, but is needed to properly
>     support Config.in options declared in BR2_EXTERNAL (next commit).

  It would make more sense to do it in that commit then, but that's just 
nitpicking.

>
>   * Passes the BR2_EXTERNAL into the *config environment, so that its
>     value is found when parsing/evaluating Config.in files and .config
>     values.

  That's pretty useless in this commit, since it anyway doesn't end up in 
.config and isn't used in Config.in.

>
>   * Encodes the BR2_EXTERNAL value into the Makefile wrapper (only if
>     BR2_EXTERNAL is specified by the user, not if the dummy internal
>     value is used).
>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
>   Config.in                  |  4 ++++
>   Makefile                   | 13 +++++++++++--
>   support/scripts/mkmakefile |  3 ++-
>   3 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/Config.in b/Config.in
> index 65c29b4..522eaf8 100644
> --- a/Config.in
> +++ b/Config.in
> @@ -14,6 +14,10 @@ config BR2_HOSTARCH
>   	string
>   	option env="HOSTARCH"
>
> +config BR2_EXTERNAL
> +	string
> +	option env="BR2_EXTERNAL"
> +

  If you agree to store the value in the .config file, it could look 
something like this.

-------

config BR2_EXTERNAL_FROM_ENV
         string
         option env="BR2_EXTERNAL"

# This condition forces the user to set BR2_EXTERNAL from the
# command line the first time.
if BR2_EXTERNAL_FROM_ENV != ""
config BR2_EXTERNAL
         string "External buildroot add-ons"
         default BR2_EXTERNAL_FROM_ENV
         help
           List of directories with buildroot add-ons. ...
endif

if BR2_EXTERNAL != BR2_EXTERNAL_FROM_ENV
comment "You need to re-run the config to see the new packages"
endif


-------

  It doesn't really work, though, because currently the .config is not 
read in when doing 'make menuconfig', so that BR2_EXTERNAL_FROM_ENV will 
always be "". But I'm sure we'll be able to find something that works 
with a little more effort.


>   # 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 8610592..13ad342 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -51,6 +51,14 @@ CONFIG_CONFIG_IN=Config.in
>   CONFIG=support/kconfig
>   DATE:=$(shell date +%Y%m%d)
>
> +# Turn BR2_EXTERNAL into an absolute path
> +ifneq ($(BR2_EXTERNAL),)
> +override BR2_EXTERNAL := $(realpath $(BR2_EXTERNAL))
> +BR2_EXTERNAL_USED = y
> +else
> +BR2_EXTERNAL = $(TOPDIR)/support/dummy-external/
> +endif
> +
>   # Compute the full local version string so packages can use it as-is
>   # Need to export it, so it can be got from environment in children (eg. mconf)
>   export BR2_VERSION_FULL:=$(BR2_VERSION)$(shell $(TOPDIR)/support/scripts/setlocalversion)
> @@ -632,7 +640,8 @@ COMMON_CONFIG_ENV = \
>   	KCONFIG_AUTOCONFIG=$(BUILD_DIR)/buildroot-config/auto.conf \
>   	KCONFIG_AUTOHEADER=$(BUILD_DIR)/buildroot-config/autoconf.h \
>   	KCONFIG_TRISTATE=$(BUILD_DIR)/buildroot-config/tristate.config \
> -	BUILDROOT_CONFIG=$(BUILDROOT_CONFIG)
> +	BUILDROOT_CONFIG=$(BUILDROOT_CONFIG) \
> +	BR2_EXTERNAL=$(BR2_EXTERNAL)
>
>   xconfig: $(BUILD_DIR)/buildroot-config/qconf outputmakefile
>   	@mkdir -p $(BUILD_DIR)/buildroot-config
> @@ -739,7 +748,7 @@ source-check:
>   # output directory.
>   outputmakefile:
>   ifeq ($(NEED_WRAPPER),y)
> -	$(Q)$(TOPDIR)/support/scripts/mkmakefile $(TOPDIR) $(O)
> +	$(Q)$(TOPDIR)/support/scripts/mkmakefile $(TOPDIR) $(O) $(if $(BR2_EXTERNAL_USED),$(BR2_EXTERNAL))
>   endif
>
>   # printvars prints all the variables currently defined in our Makefiles
> diff --git a/support/scripts/mkmakefile b/support/scripts/mkmakefile
> index cef2ec7..e7c1bd0 100755
> --- a/support/scripts/mkmakefile
> +++ b/support/scripts/mkmakefile
> @@ -6,7 +6,7 @@
>   # Usage
>   # $1 - Kernel src directory
>   # $2 - Output directory
> -
> +# $3 - BR2_EXTERNAL directory
>
>   test ! -r $2/Makefile -o -O $2/Makefile || exit 0
>   # Only overwrite automatically generated Makefiles
> @@ -27,6 +27,7 @@ makedir := \$(dir \$(call lastword,\$(MAKEFILE_LIST)))
>
>   MAKEARGS := -C $1
>   MAKEARGS += O=\$(if \$(patsubst /%,,\$(makedir)),\$(CURDIR)/)\$(patsubst %/,%,\$(makedir))
> +MAKEARGS += BR2_EXTERNAL=$3

  Obviously, this won't be needed anymore if the EXTERNAL is stored in 
the .config.


  Regards,
  Arnout

>
>   MAKEFLAGS += --no-print-directory
>
>


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
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