From 910b40468a9ce3f2f5d48c5d260329c27d45adb5 Mon Sep 17 00:00:00 2001
From: Sam Ravnborg <sam@neptun.(none)>
Date: Fri, 19 Oct 2007 21:46:01 +0200
Subject: [PATCH] kbuild: introduce cc-cross-prefix

cc-cross-prefix is useful for the architecture that like
to provide a default CROSS_COMPILE value,
but may have several to select between.

Sample usage:

ifneq ($(SUBARCH),$(ARCH))
        ifeq ($(CROSS_COMPILE),)
               CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-)
        endif
endif

Actual usage by the different archs will taken care of later.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
---
 Documentation/kbuild/makefiles.txt | 22 ++++++++++++++++++++++
 scripts/Kbuild.include             | 11 +++++++++++
 2 files changed, 33 insertions(+)

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index f099b814d38..6166e2d7da7 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -518,6 +518,28 @@ more details, with real examples.
 	In this example for a specific GCC version the build will error out explaining
 	to the user why it stops.
 
+    cc-cross-prefix
+	cc-cross-prefix is used to check if there exist a $(CC) in path with
+	one of the listed prefixes. The first prefix where there exist a
+	prefix$(CC) in the PATH is returned - and if no prefix$(CC) is found
+	then nothing is returned.
+	Additional prefixes are separated by a single space in the
+	call of cc-cross-prefix.
+	This functionality is usefull for architecture Makefile that try
+	to set CROSS_COMPILE to well know values but may have several
+	values to select between.
+	It is recommended only to try to set CROSS_COMPILE is it is a cross
+	build (host arch is different from target arch). And is CROSS_COMPILE
+	is already set then leave it with the old value.
+
+	Example:
+		#arch/m68k/Makefile
+		ifneq ($(SUBARCH),$(ARCH))
+		        ifeq ($(CROSS_COMPILE),)
+		               CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu-)
+			endif
+		endif
+
 === 4 Host Program support
 
 Kbuild supports building executables on the host for use during the
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index de7bb284c61..b96ea8d6a5e 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -56,6 +56,17 @@ endef
 # gcc support functions
 # See documentation in Documentation/kbuild/makefiles.txt
 
+# cc-cross-prefix
+# Usage: CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-)
+# Return first prefix where a prefix$(CC) is found in PATH.
+# If no $(CC) found in PATH with listed prefixes return nothing
+cc-cross-prefix =  \
+	$(word 1, $(foreach c,$(1),                                   \
+		$(shell set -e;                                       \
+		if (which $(strip $(c))$(CC)) > /dev/null 2>&1 ; then \
+			echo $(c);                                    \
+		fi)))
+
 # output directory for tests below
 TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)
 
-- 
2.20.1