On Mon, May 25, 2020 at 12:43 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:
>
> $(firstword ...) in scripts/Makefile.modpost was added by commit
> 3f3fd3c05585 ("[PATCH] kbuild: allow multi-word $M in Makefile.modpost")
> to build multiple external module directories.
>
> It was a solution to resolve symbol dependencies when an external
> module depends on another external module.
>
> Commit 0d96fb20b7ed ("kbuild: Add new Kbuild variable
> KBUILD_EXTRA_SYMBOLS") introduced another solution by passing symbol
> info via KBUILD_EXTRA_SYMBOLS, then broke the multi-word M= support.
>
> include $(if $(wildcard $(KBUILD_EXTMOD)/Kbuild), \
> $(KBUILD_EXTMOD)/Kbuild, $(KBUILD_EXTMOD)/Makefile)
>
> ... does not work if KBUILD_EXTMOD contains multiple words.
>
> This feature has been broken for more than a decade. Remove the
> bitrotten code, and stop parsing if M or KBUILD_EXTMOD contains
> multiple words.
>
> As Documentation/kbuild/modules.rst explains, if your module depends
> on another one, there are two solutions:
> - add a common top-level Kbuild file
> - use KBUILD_EXTRA_SYMBOLS
>
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
This patch, applied to linux-kbuild.
> ---
>
> Changes in v2:
> - Add more commit log
>
> Makefile | 3 +++
> scripts/Makefile.modpost | 2 +-
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 72eb55a36545..48a2dfaf3bf3 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -218,6 +218,9 @@ ifeq ("$(origin M)", "command line")
> KBUILD_EXTMOD := $(M)
> endif
>
> +$(if $(word 2, $(KBUILD_EXTMOD)), \
> + $(error building multiple external modules is not supported))
> +
> export KBUILD_CHECKSRC KBUILD_EXTMOD
>
> extmod-prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> index 957eed6a17a5..b79bf0e30d32 100644
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -44,7 +44,7 @@ include include/config/auto.conf
> include scripts/Kbuild.include
>
> kernelsymfile := $(objtree)/Module.symvers
> -modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
> +modulesymfile := $(KBUILD_EXTMOD)/Module.symvers
>
> MODPOST = scripts/mod/modpost \
> $(if $(CONFIG_MODVERSIONS),-m) \
> --
> 2.25.1
>
--
Best Regards
Masahiro Yamada
