Re: [PATCH 19/23] kbuild: support building external modules in a separate build directory

[Masahiro Yamada <masahiroy@kernel.org>]

On Fri, Oct 4, 2024 at 4:47 AM Nicolas Schier <nicolas@fjasle.eu> wrote:

> > @@ -109,6 +109,9 @@ executed to make module versioning work.
> >               directory where the external module (kbuild file) is
> >               located.
> >
> > +     MO=$BUILD_DIR
> > +             Speficies a separate output directory for the external module.
>
> s/Speficies/Specifies/

Thanks, I will fix.

>
> > +
> >  2.3 Targets
> >  ===========
> >
> > diff --git a/Makefile b/Makefile
> > index 9fbf7ef6e394..b654baa0763a 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -134,6 +134,10 @@ ifeq ("$(origin M)", "command line")
> >    KBUILD_EXTMOD := $(M)
> >  endif
> >
> > +ifeq ("$(origin MO)", "command line")
> > +  KBUILD_EXTMOD_OUTPUT := $(MO)
> > +endif
> > +
> >  $(if $(word 2, $(KBUILD_EXTMOD)), \
> >       $(error building multiple external modules is not supported))
>
> Should we also check against multiple output directories?


I do not think so.

When a directory path contains a space,
it should be treated as-is, in general.

However, GNU Make is not good at handling spaces in files paths.

So, this will fail eventually (with a little more obscure way).

$ make O=build  M=fs/btrfs MO='/tmp/AA BB/btffs'
Makefile:214: *** failed to create output directory "/tmp/AA BB/btffs".  Stop.






> > -export building_out_of_srctree srctree VPATH
> > +ifeq ($(realpath $(_vpath)),$(CURDIR))
>
> Just a style consistency question: 'ifeq (,)' with a space after ',' (as a few
> lines above) or without as used here?

Maybe, we should keep consistency.

But, this line will be removed in v2.






--
Best Regards
Masahiro Yamada