SUBDIRS has been kept as a backward compatibility since
commit ("[PATCH] kbuild: external module support") in 2002.
We do not need multiple ways to do the same thing, so I will remove
SUBDIRS after the Linux 5.3 release. I cleaned up in-tree code, and
updated the document so that nobody would try to use it.
Meanwhile, display the following warning if SUBDIRS is used.
Makefile:189: ================= WARNING ================
Makefile:190: 'SUBDIRS' will be removed after Linux 5.3
Makefile:191: Please use 'M=' or 'KBUILD_EXTMOD' instead
Signed-off-by: Masahiro Yamada <firstname.lastname@example.org>
Acked-by: Boris Brezillon <email@example.com> # for scx200_docflash.c
Acked-by: Guenter Roeck <firstname.lastname@example.org> # for scx200_wdt.c