Re: [PATCH 22/23] kbuild: make wrapper Makefile more convenient for external modules

[Nicolas Schier]

On Tue, Sep 17, 2024 at 11:16:50PM +0900, Masahiro Yamada wrote:
> When Kbuild starts building in a separate output directory, it generates
> a wrapper Makefile, allowing you to invoke 'make' from the output
> directory.
> 
> This commit makes it more convenient, so you can invoke 'make' without
> M= or MO=.
> 
> First, you need to build external modules in a separate directory:
> 
>   $ make M=/path/to/module/source/dir MO=/path/to/module/build/dir
> 
> Once the wrapper Makefile is generated in /path/to/module/build/dir,
> you can proceed as follows:
> 
>   $ cd /path/to/module/build/dir
>   $ make
> 
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> ---
> 
>  Makefile | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 9f0ba07e8f25..81603a50c757 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -641,10 +641,20 @@ ifdef building_out_of_srctree
>  # At the same time when output Makefile generated, generate .gitignore to
>  # ignore whole output directory
>  
> +ifdef KBUILD_EXTMOD
> +print_env_for_makefile = \
> +	echo "export KBUILD_OUTPUT = $(objtree)"; \
> +	echo "export KBUILD_EXTMOD = $(_vpath)" ; \
> +	echo "export KBUILD_EXTMOD_OUTPUT = $(CURDIR)"
> +else
> +print_env_for_makefile = \
> +	echo "export KBUILD_OUTPUT = $(CURDIR)"
> +endif
> +
>  quiet_cmd_makefile = GEN     Makefile
>        cmd_makefile = { \
>  	echo "\# Automatically generated by $(abs_srctree)/Makefile: don't edit"; \
> -	echo "export KBUILD_OUTPUT = $(CURDIR)"; \
> +	$(print_env_for_makefile); \
>  	echo "include $(abs_srctree)/Makefile"; \
>  	} > Makefile
>  
> -- 
> 2.43.0

Nice idea, thanks!

Reviewed-by: Nicolas Schier <nicolas@xxxxxxxxx>