kbuild: Simplify rule for just building one subdir

It's possible to say "make <subdir>", to descend into that subdir
and recursively build things there. This patch provides this
facility generally without the arch Makefiles needing to duplicate
it for arch/$(ARCH)/somedir.

Makefile

@@ -215,15 +215,12 @@ vmlinux: $(CONFIGURATION) $(vmlinux-objs) dummy
 #	The actual objects are generated when descending, 
 #	make sure no implicit rule kicks in
 
-$(sort $(vmlinux-objs)): linuxsubdirs ;
+$(sort $(vmlinux-objs)): $(SUBDIRS) ;
 
 # 	Handle descending into subdirectories listed in $(SUBDIRS)
 
-.PHONY: linuxsubdirs
-linuxsubdirs: $(patsubst %, _dir_%, $(SUBDIRS))
-
-$(patsubst %, _dir_%, $(SUBDIRS)) : dummy include/linux/version.h include/config/MARKER
-	@$(MAKE) -C $(patsubst _dir_%, %, $@)
+$(SUBDIRS): dummy include/linux/version.h include/config/MARKER
+	@$(MAKE) -C $@
 
 # Configuration
 # ---------------------------------------------------------------------------
@@ -489,13 +486,6 @@ tags: dummy
 	find include -type d \( -name "asm-*" -o -name config \) -prune -o -name '*.h' -print | xargs ctags $$CTAGSF -a && \
 	find $(SUBDIRS) init -name '*.[ch]' | xargs ctags $$CTAGSF -a
 
-# Targets which will only descend into one subdir, not trying
-# to link vmlinux afterwards
-# FIXME: anybody still using this?
-
-fs lib mm ipc kernel drivers net sound: dummy
-	$(MAKE) $(subst $@, _dir_$@, $@)
-
 # Make a backup
 # FIXME anybody still using this?
 

arch/arm/Makefile

@@ -212,9 +212,6 @@ vmlinux: arch/arm/vmlinux.lds
 arch/arm/vmlinux.lds: $(LDSCRIPT) dummy
 	@sed 's/TEXTADDR/$(TEXTADDR)/;s/DATAADDR/$(DATAADDR)/' $(LDSCRIPT) >$@
 
-arch/arm/kernel arch/arm/mm arch/arm/lib: dummy
-	$(MAKE) CFLAGS="$(CFLAGS) $(CFLAGS_KERNEL)" $(subst $@, _dir_$@, $@)
-
 bzImage zImage zinstall Image bootpImage install: vmlinux
 	@$(MAKEBOOT) $@
 

arch/cris/Makefile

@@ -61,12 +61,6 @@ DRIVERS += arch/cris/drivers/drivers.o
 LIBGCC = $(shell $(CC) $(CFLAGS) -print-file-name=libgcc.a)
 LIBS := $(TOPDIR)/arch/cris/lib/lib.a $(LIBS) $(TOPDIR)/arch/cris/lib/lib.a $(LIBGCC)
 
-arch/cris/kernel: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/cris/kernel
-
-arch/cris/mm: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/cris/mm
-
 MAKEBOOT = $(MAKE) -C arch/$(ARCH)/boot
 
 vmlinux.bin: vmlinux

arch/i386/Makefile

@@ -103,12 +103,6 @@ SUBDIRS	+= arch/i386/pci
 DRIVERS	+= arch/i386/pci/pci.o
 endif
 
-arch/i386/kernel: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/i386/kernel
-
-arch/i386/mm: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/i386/mm
-
 MAKEBOOT = $(MAKE) -C arch/$(ARCH)/boot
 
 vmlinux: arch/i386/vmlinux.lds

arch/parisc/Makefile

@@ -55,17 +55,8 @@ endif
 ifdef CONFIG_KWDB
 SUBDIRS := $(SUBDIRS) arch/parisc/kdb
 DRIVERS := $(DRIVERS) arch/parisc/kdb/kdb.o
-
-arch/parisc/kdb: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/parisc/kdb
 endif
 
-arch/parisc/kernel: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/parisc/kernel
-
-arch/parisc/mm: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/parisc/mm
-
 palo: vmlinux
 	export TOPDIR=`pwd`; export CONFIG_STI_CONSOLE=$(CONFIG_STI_CONSOLE); \
 	unset STRIP LDFLAGS CPP CPPFLAGS AFLAGS CFLAGS CC LD; cd ../palo && make lifimage

arch/s390/Makefile

@@ -44,15 +44,6 @@ all: image listing
 listing: vmlinux
 	@$(MAKEBOOT) listing
 
-arch/s390/kernel: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/s390/kernel
-
-arch/s390/mm: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/s390/mm
-
-drivers/s390: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=drivers/s390
-
 MAKEBOOT = $(MAKE) -C arch/$(ARCH)/boot
 
 image: vmlinux 

arch/s390x/Makefile

@@ -41,15 +41,6 @@ all: image listing
 listing: vmlinux
 	@$(MAKEBOOT) listing
 
-arch/s390x/kernel: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/s390x/kernel
-
-arch/s390x/mm: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/s390x/mm
-
-drivers/s390: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=drivers/s390
-
 MAKEBOOT = $(MAKE) -C arch/$(ARCH)/boot
 
 image: vmlinux 

arch/x86_64/Makefile

@@ -70,15 +70,6 @@ endif
 
 CORE_FILES += $(core-y)
 
-arch/x86_64/tools: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/x86_64/tools 
-
-arch/x86_64/kernel: dummy 
-	$(MAKE) linuxsubdirs SUBDIRS=arch/x86_64/kernel
-
-arch/x86_64/mm: dummy
-	$(MAKE) linuxsubdirs SUBDIRS=arch/x86_64/mm
-
 MAKEBOOT = $(MAKE) -C arch/$(ARCH)/boot
 
 vmlinux: arch/x86_64/vmlinux.lds