On Tue, Feb 28, 2023 at 12:13 PM David Gow <davidgow@xxxxxxxxxx> wrote: > > THe kbuild documentation already notes that, where there's an obj-y > target in a subdirectory, it will be orphaned if the subdirectory uses > obj-m. Suggest a way of forcing the directory to obj-y when it's based > on a config option which could be 'm'. > > Linus made several suggestions as to how this is usually done here: > https://lore.kernel.org/linux-kselftest/CAHk-=wgK07PQ_DBBbAbSJ41t__6de1xZ6q7RRu-JS=2SU0wqLQ@xxxxxxxxxxxxxx/ > > This only documents the first one, which seems most common. > > Signed-off-by: David Gow <davidgow@xxxxxxxxxx> > --- > Documentation/kbuild/makefiles.rst | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst > index e67eb261c9b0..d9eb24799f52 100644 > --- a/Documentation/kbuild/makefiles.rst > +++ b/Documentation/kbuild/makefiles.rst > @@ -254,6 +254,17 @@ from that directory will be linked into vmlinux. If the Makefile in > that directory specifies obj-y, those objects will be left orphan. > It is very likely a bug of the Makefile or of dependencies in Kconfig. > > +This means that, if a directory contains both obj-y and obj-m targets, > +it should be added with obj-y. If this directory nevertheless should > +only be built when a config option is enabled (typically to support > +a module which requires one or two files to nevertheless be built-in), > +'subst m,y' can be used to ensure obj-y is used. > + > +Example:: > + > + #drivers/Makefile > + obj-$(subst m,y,$(CONFIG_HYPERV)) += hv/ > + I think many subsystems simply do obj-y += hv/ I do not think we need to advertise hyperv's way since it does not look very pretty. Mostly, it looks like this: obj-y += kunit/ and obj-$(CONFIG_KUNIT_HOOK) += hook.o Bikeshed: I think Linus' suggestion is OK, but the BSD style seems less ugly, of course, that is just a matter of style. obj-$(CONFIG_HYPERV:m=y) += kunit/ > Kbuild also supports dedicated syntax, subdir-y and subdir-m, for > descending into subdirectories. It is a good fit when you know they > do not contain kernel-space objects at all. A typical usage is to let > -- > 2.39.2.722.g9855ee24e9-goog > -- Best Regards Masahiro Yamada
