kbuild: do not create orphan built-in.a or obj-y objects
Both 'obj-y += foo/' and 'obj-m += foo/' request Kbuild to visit the
sub-directory foo/, but the difference is that only the former combines
foo/built-in.a into the built-in.a of the current directory because
everything in sub-directories visited by obj-m is supposed to be modular.
So, it makes sense to create built-in.a only if that sub-directory is
reachable by the chain of obj-y. Otherwise, built-in.a will not be
linked into vmlinux anyway. For the same reason, it is pointless to
compile obj-y objects in the directory visited by obj-m.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 3fa32f8..724aa3e 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -35,7 +35,11 @@
subdir-y += $(__subdir-y)
__subdir-m := $(patsubst %/,%,$(filter %/, $(obj-m)))
subdir-m += $(__subdir-m)
+ifdef need-builtin
obj-y := $(patsubst %/, %/built-in.a, $(obj-y))
+else
+obj-y := $(filter-out %/, $(obj-y))
+endif
obj-m := $(filter-out %/, $(obj-m))
# Subdirectories we need to descend into