From ce37b383a0979576b35c725f601e89e4ac5b3e0e Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@nicira.com>
Date: Fri, 17 Apr 2009 14:59:03 -0700
Subject: [PATCH] datapath: Define ERR_CAST on kernels that don't already have
 it.

ERR_CAST was introduced in Linux 2.6.25 but it is also backported into the
Red Hat 2.6.18, so we need a configure-time check.
---
 acinclude.m4                                  |  2 ++
 .../linux-2.6/compat-2.6/include/linux/err.h  | 21 +++++++++++++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 datapath/linux-2.6/compat-2.6/include/linux/err.h

diff --git a/acinclude.m4 b/acinclude.m4
index 1fc71f4b..a31c7283 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -135,6 +135,8 @@ AC_DEFUN([OFP_CHECK_LINUX26_COMPAT], [
                   [OFP_DEFINE([HAVE_SKB_COPY_FROM_LINEAR_DATA_OFFSET])])
   OFP_GREP_IFELSE([$KSRC26/include/net/netlink.h], [NLA_NUL_STRING],
                   [OFP_DEFINE([HAVE_NLA_NUL_STRING])])
+  OFP_GREP_IFELSE([$KSRC26/include/linux/err.h], [ERR_CAST],
+                  [OFP_DEFINE([HAVE_ERR_CAST])])
   OFP_CHECK_LOG2_H
   OFP_CHECK_VETH
   if cmp -s datapath/linux-2.6/kcompat.h.new \
diff --git a/datapath/linux-2.6/compat-2.6/include/linux/err.h b/datapath/linux-2.6/compat-2.6/include/linux/err.h
new file mode 100644
index 00000000..50faf2a1
--- /dev/null
+++ b/datapath/linux-2.6/compat-2.6/include/linux/err.h
@@ -0,0 +1,21 @@
+#ifndef __LINUX_ERR_WRAPPER_H
+#define __LINUX_ERR_WRAPPER_H 1
+
+#include_next <linux/err.h>
+
+#ifndef HAVE_ERR_CAST
+/**
+ * ERR_CAST - Explicitly cast an error-valued pointer to another pointer type
+ * @ptr: The pointer to cast.
+ *
+ * Explicitly cast an error-valued pointer to another pointer type in such a
+ * way as to make it clear that's what's going on.
+ */
+static inline void *ERR_CAST(const void *ptr)
+{
+	/* cast away the const */
+	return (void *) ptr;
+}
+#endif /* HAVE_ERR_CAST */
+
+#endif
-- 
2.30.2