Both 'obj-y += foo/' and 'obj-m += foo/' requrest 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. If an orphan built-in.a is created, it is
very likely a Makefile bug.
Signed-off-by: Masahiro Yamada <[email protected]>
---
scripts/Makefile.build | 2 +-
scripts/Makefile.lib | 4 ++++
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 9fa09361aa5d..54fc68168686 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -66,7 +66,7 @@ lib-target := $(obj)/lib.a
real-obj-y += $(obj)/lib-ksyms.o
endif
-ifneq ($(strip $(real-obj-y) $(need-builtin)),)
+ifdef need-builtin
builtin-target := $(obj)/built-in.a
endif
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 264611972c4a..07095d3789a1 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -35,7 +35,11 @@ __subdir-y := $(patsubst %/,%,$(filter %/, $(obj-y)))
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
--
2.17.1