Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

===================================================================
RCS file: /ftp/cvs/cvsroot/src/sys/external/bsd/drm2/include/linux/kref.h,v
rcsdiff: /ftp/cvs/cvsroot/src/sys/external/bsd/drm2/include/linux/kref.h,v: warning: Unknown phrases like `commitid ...;' are present.
retrieving revision 1.1
retrieving revision 1.2
diff -u -p -r1.1 -r1.2
--- src/sys/external/bsd/drm2/include/linux/kref.h	2013/07/24 00:33:12	1.1
+++ src/sys/external/bsd/drm2/include/linux/kref.h	2014/03/18 18:20:43	1.2
@@ -0,0 +1,111 @@
+/*	$NetBSD: kref.h,v 1.2 2014/03/18 18:20:43 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2013 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Taylor R. Campbell.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _LINUX_KREF_H_
+#define _LINUX_KREF_H_
+
+#include <sys/types.h>
+#include <sys/atomic.h>
+#include <sys/systm.h>
+
+#include <linux/mutex.h>
+
+struct kref {
+	unsigned int kr_count;
+};
+
+static inline void
+kref_init(struct kref *kref)
+{
+	kref->kr_count = 1;
+}
+
+static inline void
+kref_get(struct kref *kref)
+{
+	const unsigned int count __unused =
+	    atomic_inc_uint_nv(&kref->kr_count);
+
+	KASSERTMSG((count > 1), "getting released kref");
+}
+
+static inline int
+kref_sub(struct kref *kref, unsigned int count, void (*release)(struct kref *))
+{
+	unsigned int old, new;
+
+	do {
+		old = kref->kr_count;
+		KASSERTMSG((count <= old), "overreleasing kref: %u - %u",
+		    old, count);
+		new = (old - count);
+	} while (atomic_cas_uint(&kref->kr_count, old, new) != old);
+
+	if (new == 0) {
+		(*release)(kref);
+		return 1;
+	}
+
+	return 0;
+}
+
+static inline int
+kref_put(struct kref *kref, void (*release)(struct kref *))
+{
+
+	return kref_sub(kref, 1, release);
+}
+
+static inline int
+kref_put_mutex(struct kref *kref, void (*release)(struct kref *),
+    struct mutex *interlock)
+{
+	unsigned int old, new;
+
+	do {
+		old = kref->kr_count;
+		KASSERT(old > 0);
+		if (old == 1) {
+			mutex_lock(interlock);
+			if (atomic_add_int_nv(&kref->kr_count, -1) == 0) {
+				(*release)(kref);
+				return 1;
+			}
+			mutex_unlock(interlock);
+			return 0;
+		}
+		new = (old - 1);
+	} while (atomic_cas_uint(&kref->kr_count, old, new) != old);
+
+	return 0;
+}
+
+#endif  /* _LINUX_KREF_H_ */