[Buildroot] [PATCH 13/16 v3] core: add support for multiple br2-external trees

[Thomas Petazzoni]

Hello,

On Sun, 17 Jul 2016 12:34:33 +0200, Yann E. MORIN wrote:

> What we do is to treat BR2_EXTERNAL as a space-separated list of paths,
> which we iterate to construct:

As discussed on IRC, is the space-separated list the best choice? Most
environment variables that contain paths in Unix are colon-separated
instead (PATH, LD_LIBRARY_PATH, PKG_CONFIG_PATH, etc, etc.)

Making it space-separated makes it a bit annoying IMO.

> -# This needs to be *after* we compute BR_EXTERNAL, above.
>  .PHONY: $(BR2_EXTERNAL_FILE)
>  $(BR2_EXTERNAL_FILE):
> -	@echo BR2_EXTERNAL ?= $(BR_EXTERNAL) >$@
> +	@echo BR2_EXTERNAL ?= $(BR2_EXTERNAL) >$@
> +
> +# Those two variables need to be defined as simply-expanded variables, they
> +# can't be recursively-expanded, because the values they are assigned change
> +# with each iteration of the foreach, below.
> +BR_EXTERNAL_IDS :=
> +EXTRA_ENV :=
> +
> +# If there is no or one br2-external trees used, then we don't require (but
> +# accept) an ID; otherwise (i.e. there are two or more br2-external trees)
> +# we require they do all define their ID.
> +ifeq ($(filter-out 0 1,$(words $(BR2_EXTERNAL))),)
> +BR2_EXTERNAL_NEED_ID := loose
> +else
> +BR2_EXTERNAL_NEED_ID := strict
> +endif
> +
> +# Validate the br2-external tree passed as $(1):
> +# - check the directory actually exists
> +# - check if we need and have a non-empty ID
> +# - check the ID is not a duplicate
> +# - set variables for later use
> +define BR2_EXTERNAL_VALIDATE
> +  _BR_EXT_DIR := $$(shell cd $(1) >/dev/null 2>&1 && pwd)
> +  ifeq ($$(_BR_EXT_DIR),)
> +    $$(error BR2_EXTERNAL='$(1)' does not exist, relative to $$(TOPDIR))
> +  endif
> +  _BR_EXT_ID := $$(shell cat $$(_BR_EXT_DIR)/external.id 2>/dev/null)
> +  ifeq ($$(_BR_EXT_ID),)
> +    ifeq ($(BR2_EXTERNAL_NEED_ID),strict)
> +      $$(error BR2_EXTERNAL='$(1)' has no ID (in file 'external.id'),\
> +               mandatory to use more than one br2-external tree at once)
> +    endif # BR2_EXTERNAL_NEED_ID strict
> +  endif # No ID
> +  ifneq ($$(filter $$(_BR_EXT_ID),$$(BR_EXTERNAL_IDS)),)
> +    $$(error Duplicate ID '$$(_BR_EXT_ID)' in '$(1)', previously defined in '$$(BR2_EXTERNAL_$$(_BR_EXT_ID))')
> +  endif
> +  ifneq ($$(_BR_EXT_ID),)
> +    BR2_EXTERNAL_$$(_BR_EXT_ID) := $$(_BR_EXT_DIR)
> +    BR_EXTERNAL_IDS += $$(_BR_EXT_ID)
> +    EXTRA_ENV += BR2_EXTERNAL_$$(_BR_EXT_ID)=$$(_BR_EXT_DIR)
> +  endif # _BR_EXT_ID not empty
> +endef # BR2_EXTERNAL_VALIDATE

This is really long and not so pretty to look at. Perhaps all the
"validation" aspects can be handled in the shell script that generates
the .br2-external.in Config.in snippet?

>  # 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
> @@ -787,7 +813,7 @@ 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) \
> +	BR2_EXTERNAL="$(BR2_EXTERNAL)" \
>  	HOST_GCC_VERSION="$(HOSTCC_VERSION)" \
>  	BUILD_DIR=$(BUILD_DIR) \
>  	SKIP_LEGACY=
> @@ -895,12 +921,25 @@ $(BUILD_DIR)/.br2-external.in: $(BUILD_DIR)
>  	$(Q)if [ -n '$(BR2_EXTERNAL)' ]; then \
>  		printf "#\n# Automatically generated file; DO NOT EDIT.\n#\n\n"; \
>  		printf 'menu "User-provided options"\n\n'; \
> -		if [ -z "$(BR2_EXTERNAL_ID)" ]; then \
> +		if [ -z "$(call strip,$(BR_EXTERNAL_IDS))" ]; then \
> +			printf 'comment "%s"\n\n' $(BR2_EXTERNAL); \
>  			printf 'source "%s/Config.in"\n\n' $$(cd $(BR2_EXTERNAL) >/dev/null 2>&1 && pwd); \
>  		else \
> -			printf 'config BR2_EXTERNAL_%s\n' $(BR2_EXTERNAL_ID); \
> -			printf '\tstring\n\tdefault "%s"\n\n' $(BR2_EXTERNAL_$(BR2_EXTERNAL_ID)); \
> -			printf 'source "$$BR2_EXTERNAL_%s/Config.in"\n\n' $(BR2_EXTERNAL_ID); \
> +			$(foreach id,$(BR_EXTERNAL_IDS),\
> +				for i in $$(seq 1 80); do printf '#'; done; printf '\n\n'; \
> +				if [ $(words $(call strip,$(BR_EXTERNAL_IDS))) -gt 1 ]; then \
> +					printf 'menu "BR2_EXTERNAL_%s"\n\n' $(id); \
> +				else \
> +					printf 'comment "BR2_EXTERNAL_%s"\n\n' $(id); \
> +				fi; \
> +				printf 'comment "%s"\n\n' $(BR2_EXTERNAL_$(id)); \
> +				printf 'config BR2_EXTERNAL_%s\n' $(id); \
> +				printf '\tstring\n\tdefault "%s"\n\n' $(BR2_EXTERNAL_$(id)); \
> +				printf 'source "$$BR2_EXTERNAL_%s/Config.in"\n\n' $(id); \
> +				if [ $(words $(call strip,$(BR_EXTERNAL_IDS))) -gt 1 ]; then \
> +					printf 'endmenu # BR2_EXTERNAL_%s\n\n' $(id); \
> +				fi; ) \
> +			for i in $$(seq 1 80); do printf '#'; done; printf '\n\n'; \
>  		fi; \
>  		printf 'endmenu # User-provided options\n'; \

This is really where you want to start having a helper shell script IMO.

> -ifneq ($(wildcard $(BR2_EXTERNAL)/configs/*_defconfig),)
> +ifneq ($(wildcard $(patsubst %,%/configs/*_defconfig,$(BR2_EXTERNAL))),)

Everywhere you use a patsubst like this, a foreach would be more
appropriate I believe:

ifneq ($(wildcard $(foreach d,$(BR2_EXTERNAL),$(d)/configs/*_defconfig))

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com