From: Bastian Blank <waldi@debian.org>
Subject: kbuild: Make the toolchain variables easily overwritable
Date: Sun, 22 Feb 2009 15:39:35 +0100
Forwarded: not-needed

Allow make variables to be overridden for each flavour by a file in
the build tree, .kernelvariables.

We currently use this for ARCH, KERNELRELEASE, CC, and in some cases
also CROSS_COMPILE, CFLAGS_KERNEL and CFLAGS_MODULE.

This file can only be read after we establish the build tree, and all
use of $(ARCH) needs to be moved after this.

Index: linux/Makefile
===================================================================
--- linux.orig/Makefile
+++ linux/Makefile
@@ -321,31 +321,6 @@ include scripts/subarch.include
 # Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
 ARCH		?= $(SUBARCH)
 
-# Architecture as present in compile.h
-UTS_MACHINE 	:= $(ARCH)
-SRCARCH 	:= $(ARCH)
-
-# Additional ARCH settings for x86
-ifeq ($(ARCH),i386)
-        SRCARCH := x86
-endif
-ifeq ($(ARCH),x86_64)
-        SRCARCH := x86
-endif
-
-# Additional ARCH settings for sparc
-ifeq ($(ARCH),sparc32)
-       SRCARCH := sparc
-endif
-ifeq ($(ARCH),sparc64)
-       SRCARCH := sparc
-endif
-
-# Additional ARCH settings for sh
-ifeq ($(ARCH),sh64)
-       SRCARCH := sh
-endif
-
 KCONFIG_CONFIG	?= .config
 export KCONFIG_CONFIG
 
@@ -399,6 +374,30 @@ CFLAGS_KERNEL	=
 AFLAGS_KERNEL	=
 LDFLAGS_vmlinux =
 
+-include $(obj)/.kernelvariables
+
+# Architecture as present in compile.h
+UTS_MACHINE 	:= $(ARCH)
+SRCARCH 	:= $(ARCH)
+
+# Additional ARCH settings for x86
+ifeq ($(ARCH),i386)
+        SRCARCH := x86
+endif
+ifeq ($(ARCH),x86_64)
+        SRCARCH := x86
+endif
+
+# Additional ARCH settings for sparc
+ifeq ($(ARCH),sparc64)
+       SRCARCH := sparc
+endif
+
+# Additional ARCH settings for sh
+ifeq ($(ARCH),sh64)
+       SRCARCH := sh
+endif
+
 # Use USERINCLUDE when you must reference the UAPI directories only.
 USERINCLUDE    := \
 		-I$(srctree)/arch/$(SRCARCH)/include/uapi \