From 05523b1ef53855aef894d5009b92a7ec7331f57a Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Thu, 6 Jul 2006 16:06:32 +0000
Subject: [PATCH] Avoid using AC_RUN_IFELSE to check the kernel major.minor
 version, as it doesn't work when cross-compiling.

Every kernel Makefile I've looked at (at least for 2.4 and 2.6, including
those for separate kernel build directories) includes the "VERSION = x" and
"PATCHLEVEL = y" lines, so use 'sed' to extract the information from those
lines.
---
 m4/as-linux.m4 | 49 +++++++++----------------------------------------
 1 file changed, 9 insertions(+), 40 deletions(-)

diff --git a/m4/as-linux.m4 b/m4/as-linux.m4
index c4ba11d0..5449fa25 100644
--- a/m4/as-linux.m4
+++ b/m4/as-linux.m4
@@ -651,7 +651,7 @@ AC_DEFUN([AS_LINUX_CONFIG_OPTION_MODULE],
 ])
 
 dnl check for the major/minor version of the Linux source by checking
-dnl the headers
+dnl the Makefile
 dnl first argument is the linux directory
 dnl sets LINUX_VERSION_MAJOR and LINUX_VERSION_MINOR
 AC_DEFUN([AS_LINUX_VERSION_MAJOR_MINOR],
@@ -659,48 +659,17 @@ AC_DEFUN([AS_LINUX_VERSION_MAJOR_MINOR],
 	LINUX_DIR=[$1]
 	AC_MSG_CHECKING([Linux major/minor version])
 
-	if [[ ! -f "${LINUX_DIR}/include/linux/version.h" ]];then
-		AC_MSG_ERROR([The header file include/linux/version.h does not exist.
-For 2.6 kernels, it can be generated by running 'make prepare' in
-the kernel source directory.])
+	if [[ ! -f "${LINUX_DIR}/Makefile" ]];then
+		AC_MSG_ERROR([The Linux kernel Makefile does not exist.])
 	fi
         dnl the next set of tests is for figuring out version major/minor
-        dnl we make sure we have the right version.h by faking out CFLAGS
-	dnl since we want to avoid including linux/version.h and acidentally
-	dnl pick up /usr/include/linux
-	dnl we still add ${LINUX_DIR}/include so the Red Hat version can pick
-	dnl up linux/rhversion.h
-        ac_save_CFLAGS="$CFLAGS"
-        CFLAGS="$CFLAGS -I${LINUX_DIR}/include/linux -I${LINUX_DIR}/include"
-        dnl make sure we find version.h and it contains LINUX_VERSION_CODE
-        AC_COMPILE_IFELSE(AC_LANG_PROGRAM([
-#include "version.h"
-int code = LINUX_VERSION_CODE;
-]),
- :, AC_MSG_ERROR([${LINUX_DIR}/include/linux/version.h does not contain LINUX_VERSION_CODE]))
-
-
-        dnl figure out the linux kernel version major and minor
-        dnl using the LINUX_VERSION_CODE defined in include/linux/version.h
-        AC_RUN_IFELSE(AC_LANG_PROGRAM([
-#include "version.h"
-#define KERNEL_VERSION_MAJOR(code) ((code) >> 16)
-],[
-  return KERNEL_VERSION_MAJOR(LINUX_VERSION_CODE);
-]),
-		LINUX_VERSION_MAJOR=0, 
-		LINUX_VERSION_MAJOR=$?)
-        AC_RUN_IFELSE(AC_LANG_PROGRAM([
-#include "version.h"
-#define KERNEL_VERSION_MINOR(code) (((code) >> 8) % (2 << 8))
-],[
-  return KERNEL_VERSION_MINOR(LINUX_VERSION_CODE);
-]),
-		LINUX_VERSION_MINOR=0, 
-		LINUX_VERSION_MINOR=$?)
+        dnl use VERSION and PATCHLEVEL in the kernel Makefile
+	LINUX_VERSION_MAJOR=`sed -n 's/^VERSION = \([[0-9]]*\)/\1/p' "${LINUX_DIR}/Makefile"`
+	LINUX_VERSION_MINOR=`sed -n 's/^PATCHLEVEL = \([[0-9]]*\)/\1/p' "${LINUX_DIR}/Makefile"`
+	if [[ -z "$LINUX_VERSION_MAJOR" -o -z "$LINUX_VERSION_MINOR" ]]; then
+		AC_MSG_ERROR([No major/minor version information found in Linux kernel Makefile.])
+	fi
         AC_MSG_RESULT($LINUX_VERSION_MAJOR.$LINUX_VERSION_MINOR)
-	dnl restore CFLAGS
-        CFLAGS="$ac_save_CFLAGS"
 ])
 
 # COMEDI_CHECK_LINUX_KBUILD([LINUX_SOURCE_PATH], [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
-- 
2.26.2