[PATCH] kbuild: announce removal of SUBDIRS if used

[Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>]

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
Makefile:192: ==========================================

Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---

 Documentation/kbuild/kbuild.txt    | 7 +------
 Makefile                           | 4 ++++
 drivers/mtd/maps/scx200_docflash.c | 7 -------
 drivers/watchdog/scx200_wdt.c      | 7 -------
 samples/connector/Makefile         | 2 +-
 5 files changed, 6 insertions(+), 21 deletions(-)

diff --git a/Documentation/kbuild/kbuild.txt b/Documentation/kbuild/kbuild.txt
index 8390c36..c9e3d93 100644
--- a/Documentation/kbuild/kbuild.txt
+++ b/Documentation/kbuild/kbuild.txt
@@ -81,12 +81,7 @@ KBUILD_EXTMOD
 --------------------------------------------------
 Set the directory to look for the kernel source when building external
 modules.
-The directory can be specified in several ways:
-1) Use "M=..." on the command line
-2) Environment variable KBUILD_EXTMOD
-3) Environment variable SUBDIRS
-The possibilities are listed in the order they take precedence.
-Using "M=..." will always override the others.
+Setting "M=..." takes precedence over KBUILD_EXTMOD.
 
 KBUILD_OUTPUT
 --------------------------------------------------
diff --git a/Makefile b/Makefile
index 370d13b..57be5fb 100644
--- a/Makefile
+++ b/Makefile
@@ -186,6 +186,10 @@ endif
 # Old syntax make ... SUBDIRS=$PWD is still supported
 # Setting the environment variable KBUILD_EXTMOD take precedence
 ifdef SUBDIRS
+  $(warning ================= WARNING ================)
+  $(warning 'SUBDIRS' will be removed after Linux 5.3)
+  $(warning Please use 'M=' or 'KBUILD_EXTMOD' instead)
+  $(warning ==========================================)
   KBUILD_EXTMOD ?= $(SUBDIRS)
 endif
 
diff --git a/drivers/mtd/maps/scx200_docflash.c b/drivers/mtd/maps/scx200_docflash.c
index f1c1f73..7f1a0e6 100644
--- a/drivers/mtd/maps/scx200_docflash.c
+++ b/drivers/mtd/maps/scx200_docflash.c
@@ -216,10 +216,3 @@ static void __exit cleanup_scx200_docflash(void)
 
 module_init(init_scx200_docflash);
 module_exit(cleanup_scx200_docflash);
-
-/*
-    Local variables:
-        compile-command: "make -k -C ../../.. SUBDIRS=drivers/mtd/maps modules"
-        c-basic-offset: 8
-    End:
-*/
diff --git a/drivers/watchdog/scx200_wdt.c b/drivers/watchdog/scx200_wdt.c
index 836377c..ec4063e 100644
--- a/drivers/watchdog/scx200_wdt.c
+++ b/drivers/watchdog/scx200_wdt.c
@@ -262,10 +262,3 @@ static void __exit scx200_wdt_cleanup(void)
 
 module_init(scx200_wdt_init);
 module_exit(scx200_wdt_cleanup);
-
-/*
-    Local variables:
-	compile-command: "make -k -C ../.. SUBDIRS=drivers/char modules"
-	c-basic-offset: 8
-    End:
-*/
diff --git a/samples/connector/Makefile b/samples/connector/Makefile
index fe3c854..6ad7162 100644
--- a/samples/connector/Makefile
+++ b/samples/connector/Makefile
@@ -14,4 +14,4 @@ HOSTCFLAGS_ucon.o += -I$(objtree)/usr/include
 all: modules
 
 modules clean:
-	$(MAKE) -C ../.. SUBDIRS=$(CURDIR) $@
+	$(MAKE) -C ../.. M=$(CURDIR) $@
-- 
2.7.4


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