[Buildroot] [RFC 1/1] br2-external: Alow to include toolchain from external tree

[Arnout Vandecappelle]

On 17/04/2019 22:46, Vadim Kochan wrote:
> Add possibility to select toolchain from br2-external tree which
> allows to easy use custom external toolchains by selecting them via
> menuconfig as if they were integrated into buildroot.
> 
> The br2-external tree should contain:
> 
> 	${br2-external}/external-toolchain/Config.in
> 
> file to be included into external toolchains list.
> 
> All such picked toolchains are sourced in:
> 
> 	toolchain/toolchain-external/Config.in
> 
> from auto-generated file ${O}/build/.br2-external.in.toolchain.

 Bikeshedding time: I would call the file .br2-external-toolchain.in.

> 
> Added new '-t' option in support/scripts/br2-external to generate
> kconfig for the found toolchains from the all specified external trees.
> 
> Signed-off-by: Vadim Kochan <vadim4j at gmail.com>
> ---
> 
> This is just PoC to rise the discussion about this concept.
> 
>  Makefile                               |  6 +++++-
>  support/scripts/br2-external           | 36 ++++++++++++++++++++++++++++++++--
>  toolchain/toolchain-external/Config.in |  2 ++
>  3 files changed, 41 insertions(+), 3 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 522c0b0606..4eceb88813 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -938,7 +938,7 @@ HOSTCFLAGS = $(CFLAGS_FOR_BUILD)
>  export HOSTCFLAGS
>  
>  .PHONY: prepare-kconfig
> -prepare-kconfig: outputmakefile $(BUILD_DIR)/.br2-external.in
> +prepare-kconfig: outputmakefile $(BUILD_DIR)/.br2-external.in $(BUILD_DIR)/.br2-external.in.toolchain
>  
>  $(BUILD_DIR)/buildroot-config/%onf:
>  	mkdir -p $(@D)/lxdialog
> @@ -1042,6 +1042,10 @@ endif
>  $(BUILD_DIR)/.br2-external.in: $(BUILD_DIR)
>  	$(Q)support/scripts/br2-external -k -o "$(@)" $(BR2_EXTERNAL)
>  
> +.PHONY: $(BUILD_DIR)/.br2-external.in.toolchain
> +$(BUILD_DIR)/.br2-external.in.toolchain: $(BUILD_DIR)
> +	$(Q)support/scripts/br2-external -t -o "$(@)" $(BR2_EXTERNAL)

 I don't like much that it's a separate target. However, it's consistent with
how .br2-external.in is called, so it's OK as it is.


>  # printvars prints all the variables currently defined in our
>  # Makefiles. Alternatively, if a non-empty VARS variable is passed,
>  # only the variables matching the make pattern passed in VARS are
> diff --git a/support/scripts/br2-external b/support/scripts/br2-external
> index 00cb57d1ed..3ec332d93e 100755
> --- a/support/scripts/br2-external
> +++ b/support/scripts/br2-external
> @@ -16,10 +16,11 @@ main() {
>      local OPT OPTARG
>      local br2_ext ofile ofmt
>  
> -    while getopts :hkmo: OPT; do
> +    while getopts :htkmo: OPT; do
>          case "${OPT}" in
>          h)  help; exit 0;;
>          o)  ofile="${OPTARG}";;
> +        t)  ofmt="toolchain";;
>          k)  ofmt="kconfig";;
>          m)  ofmt="mk";;
>          :)  error "option '%s' expects a mandatory argument\n" "${OPTARG}";;
> @@ -30,7 +31,7 @@ main() {
>      shift $((OPTIND-1))
>  
>      case "${ofmt}" in
> -    mk|kconfig)
> +    mk|kconfig|toolchain)
>          ;;
>      *)  error "no output format specified (-m/-k)\n";;
>      esac
> @@ -188,6 +189,37 @@ do_kconfig() {
>      printf "endmenu # User-provided options\n"
>  }
>  
> +# Generate the toolchain kconfig snippet for the br2-external tree.
> +do_toolchain() {
> +    local br2_name br2_ext
> +
> +    printf '#\n# Automatically generated file; DO NOT EDIT.\n#\n'
> +    printf '\n'
> +
> +    if [ ${#BR2_EXT_NAMES[@]} -eq 0 ]; then
> +        printf '# No br2-external tree defined.\n'
> +        return
> +    fi
> +
> +    for br2_name in "${BR2_EXT_NAMES[@]}"; do
> +        eval br2_desc="\"\${BR2_EXT_DESCS_${br2_name}}\""
> +        eval br2_ext="\"\${BR2_EXT_PATHS_${br2_name}}\""
> +
> +        if [ ! -f "${br2_ext}/toolchain-external/Config.in" ]; then
> +            continue
> +	fi

 There's some whitespace confusion here; this file uses spaces only.

> +
> +        # we have to duplicate it here too because otherwise BR2_EXTERNAL_*
> +	# is not evaluated in Config.in

 Argh, that's mightily annoying... But I don't really see a better solution. The
reason is that .br2-external.in only gets included after all the other files
have already been included. Normally Kconfig is indepdent of the order in which
you declare things, but not when you use a variable in a source directive...

 I don't see a good way around it. We could have yet another
.br2-external-variables.in that gets included *before* all the rest, but that's
also pretty ugly...

 Yann, any ideas?


 Assuming there is no better solution than this one, the patch looks pretty much
OK except for the whitespace. I believe it covers all cases. It would be nice if
the file would also contain *something* if there are some externals but none of
them have a toolchain-external/Config.in, but I don't think it's worth spending
time on that.

 For the final patch there should also be documentation of course.

 Regards,
 Arnout


> +        printf 'config BR2_EXTERNAL_%s_PATH\n' "${br2_name}"
> +        printf '\tstring\n'
> +        printf '\tdefault "%s"\n' "${br2_ext}"
> +
> +        printf 'source "%s/toolchain-external/Config.in"\n' "${br2_ext}"
> +        printf '\n'
> +    done
> +}
> +
>  help() {
>      cat <<-_EOF_
>  	Usage:
> diff --git a/toolchain/toolchain-external/Config.in b/toolchain/toolchain-external/Config.in
> index d234c1c552..70e8a89e5e 100644
> --- a/toolchain/toolchain-external/Config.in
> +++ b/toolchain/toolchain-external/Config.in
> @@ -50,6 +50,8 @@ source "toolchain/toolchain-external/toolchain-external-codesourcery-amd64/Confi
>  # architecture.
>  source "toolchain/toolchain-external/toolchain-external-custom/Config.in"
>  
> +source "$BR2_BUILD_DIR/.br2-external.in.toolchain"
> +
>  endchoice
>  
>  choice
>