kconfig: fix .config dependencies

This fixes one of the worst kbuild warts left - the broken dependencies used
to check and regenerate the .config file.  This was done via an indirect
dependency and the .config itself had an empty command, which can cause make
not to reread the changed .config file.

Instead of this we generate now a new file include/config/auto.conf from
.config, which is used for kbuild and has the proper dependencies.  It's also
the main make target now for all files generated during this step (and thus
replaces include/linux/autoconf.h).

This also means we can now relax the syntax requirements for the .config file
and we don't have to rewrite it all the time, i.e.  silentoldconfig only
writes .config now when it's necessary to keep it in sync with the Kconfig
files and even this can be suppressed by setting the environment variable
KCONFIG_NOSILENTUPDATE, so the update can (and must) be done manually.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 11 insertions, 16 deletions

diff --git a/Makefile b/Makefile
index a3a7baad855..b1610562a65 100644
--- a/Makefile
+++ b/Makefile
@@ -404,7 +404,7 @@ include $(srctree)/arch/$(ARCH)/Makefile
 export KBUILD_DEFCONFIG
 
 config %config: scripts_basic outputmakefile FORCE
-	$(Q)mkdir -p include/linux
+	$(Q)mkdir -p include/linux include/config
 	$(Q)$(MAKE) $(build)=scripts/kconfig $@
 	$(Q)$(MAKE) -C $(srctree) KBUILD_SRC= .kernelrelease
 
@@ -421,8 +421,6 @@ PHONY += scripts
 scripts: scripts_basic include/config/MARKER
 	$(Q)$(MAKE) $(build)=$(@)
 
-scripts_basic: include/linux/autoconf.h
-
 # Objects we will link into vmlinux / subdirs we need to visit
 init-y		:= init/
 drivers-y	:= drivers/ sound/
@@ -436,25 +434,22 @@ ifeq ($(dot-config),1)
 
 # Read in dependencies to all Kconfig* files, make sure to run
 # oldconfig if changes are detected.
--include .kconfig.d
-
-include .config
+-include include/config/auto.conf.cmd
+-include include/config/auto.conf
 
-# If .config needs to be updated, it will be done via the dependency
-# that autoconf has on .config.
 # To avoid any implicit rule to kick in, define an empty command
-.config .kconfig.d: ;
+.config include/config/auto.conf.cmd: ;
 
-# If .config is newer than include/linux/autoconf.h, someone tinkered
+# If .config is newer than include/config/auto.conf, someone tinkered
 # with it and forgot to run make oldconfig.
-# If kconfig.d is missing then we are probarly in a cleaned tree so
+# if auto.conf.cmd is missing then we are probarly in a cleaned tree so
 # we execute the config step to be sure to catch updated Kconfig files
-include/linux/autoconf.h: .kconfig.d .config
-	$(Q)mkdir -p include/linux
+include/config/auto.conf: .config include/config/auto.conf.cmd
 	$(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig
+
 else
 # Dummy target needed, because used as prerequisite
-include/linux/autoconf.h: ;
+include/config/auto.conf: ;
 endif
 
 # The all: target is the default when no target is given on the
@@ -779,7 +774,7 @@ PHONY += prepare-all
 prepare3: .kernelrelease
 ifneq ($(KBUILD_SRC),)
 	@echo '  Using $(srctree) as source for kernel'
-	$(Q)if [ -f $(srctree)/.config ]; then \
+	$(Q)if [ -f $(srctree)/.config -o -d $(srctree)/include/config ]; then \
 		echo "  $(srctree) is not clean, please run 'make mrproper'";\
 		echo "  in the '$(srctree)' directory.";\
 		/bin/false; \
@@ -822,7 +817,7 @@ include/asm:
 
 # 	Split autoconf.h into include/linux/config/*
 
-include/config/MARKER: scripts/basic/split-include include/linux/autoconf.h
+include/config/MARKER: scripts/basic/split-include include/config/auto.conf
 	@echo '  SPLIT   include/linux/autoconf.h -> include/config/*'
 	@scripts/basic/split-include include/linux/autoconf.h include/config
 	@touch $@