The change allow to build external modules with nested makefiles.
Current unofficial way(using "src" variable) allow to build
external(out of tree) kernel module with separating source and build
artifacts dirs but with nested makefiles it doesn't work properly.
Build system trap to recursion inside makefiles, articafts output dir
path grow with each iteration until exceed max path len and build failed
This fix update "src" var during processing subdirs and resolve
recursion issue
Usage example:
make -C KERNEL_SOURCE_TREE M=BUILD_OUT_DIR src=EXT_MOD_SRC_DIR modules

Cc: Valerii Chernous <vchernou@cisco.com>
Cc: xe-linux-external@cisco.com
Signed-off-by: Valerii Chernous <vchernou@cisco.com>
---
 scripts/Makefile.build | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a293950e2e07..75ea9052ea4a 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -490,6 +490,7 @@ $(single-subdir-goals): $(single-subdirs)
 PHONY += $(subdir-ym)
 $(subdir-ym):
 	$(Q)$(MAKE) $(build)=$@ \
+	$(if $(findstring command line,$(origin src)),src=$(patsubst $(obj)/%,$(src)/%,$@)) \
 	need-builtin=$(if $(filter $@/built-in.a, $(subdir-builtin)),1) \
 	need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1) \
 	$(filter $@/%, $(single-subdir-goals))
-- 
2.35.6

On Mon, Apr 15, 2024 at 7:14 PM Valerii Chernous <vchernou@cisco.com> wrote:
>
> The change allow to build external modules with nested makefiles.
> Current unofficial way(using "src" variable) allow to build
> external(out of tree) kernel module with separating source and build
> artifacts dirs but with nested makefiles it doesn't work properly.
> Build system trap to recursion inside makefiles, articafts output dir
> path grow with each iteration until exceed max path len and build failed
> This fix update "src" var during processing subdirs and resolve
> recursion issue
> Usage example:
> make -C KERNEL_SOURCE_TREE M=BUILD_OUT_DIR src=EXT_MOD_SRC_DIR modules
>
> Cc: Valerii Chernous <vchernou@cisco.com>
> Cc: xe-linux-external@cisco.com
> Signed-off-by: Valerii Chernous <vchernou@cisco.com>


NACK.

Please do not send hacks over again.










> ---
>  scripts/Makefile.build | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index a293950e2e07..75ea9052ea4a 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -490,6 +490,7 @@ $(single-subdir-goals): $(single-subdirs)
>  PHONY += $(subdir-ym)
>  $(subdir-ym):
>         $(Q)$(MAKE) $(build)=$@ \
> +       $(if $(findstring command line,$(origin src)),src=$(patsubst $(obj)/%,$(src)/%,$@)) \
>         need-builtin=$(if $(filter $@/built-in.a, $(subdir-builtin)),1) \
>         need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1) \
>         $(filter $@/%, $(single-subdir-goals))
> --
> 2.35.6
>


-- 
Best Regards
Masahiro Yamada