diff --git a/sys/sys/kobj.h b/sys/sys/kobj.h
--- a/sys/sys/kobj.h
+++ b/sys/sys/kobj.h
@@ -131,14 +131,8 @@
  * DEFINE_CLASS_1(foo, foo_class, foo_methods, sizeof(foo_softc),
  *			  bar);
  */
-#define DEFINE_CLASS_1(name, classvar, methods, size,	\
-		       base1)				\
-							\
-static kobj_class_t name ## _baseclasses[] =		\
-	{ &base1, NULL };				\
-struct kobj_class classvar = {				\
-	#name, methods, size, name ## _baseclasses	\
-}
+#define DEFINE_CLASS_1(name, classvar, methods, size, base1) \
+	DEFINE_CLASSN(name, classvar, methods, size, base1)
 
 /*
  * Define a class inheriting two base classes. Use like this:
@@ -146,15 +140,8 @@
  * DEFINE_CLASS_2(foo, foo_class, foo_methods, sizeof(foo_softc),
  *			  bar, baz);
  */
-#define DEFINE_CLASS_2(name, classvar, methods, size,	\
-	               base1, base2)			\
-							\
-static kobj_class_t name ## _baseclasses[] =		\
-	{ &base1,					\
-	  &base2, NULL };				\
-struct kobj_class classvar = {				\
-	#name, methods, size, name ## _baseclasses	\
-}
+#define DEFINE_CLASS_2(name, classvar, methods, size, base1, base2) \
+	DEFINE_CLASSN(name, classvar, methods, size, base1, base2)
 
 /*
  * Define a class inheriting three base classes. Use like this:
@@ -162,17 +149,62 @@
  * DEFINE_CLASS_3(foo, foo_class, foo_methods, sizeof(foo_softc),
  *			  bar, baz, foobar);
  */
-#define DEFINE_CLASS_3(name, classvar, methods, size,	\
-		       base1, base2, base3)		\
-							\
-static kobj_class_t name ## _baseclasses[] =		\
-	{ &base1,					\
-	  &base2,					\
-	  &base3, NULL };				\
-struct kobj_class classvar = {				\
-	#name, methods, size, name ## _baseclasses	\
+#define DEFINE_CLASS_3(name, classvar, methods, size, base1, base2, base3) \
+	DEFINE_CLASSN(name, classvar, methods, size, base1, base2, base3)
+
+/*
+ * Define a class with unspecified visibility (presently public)
+ * inheriting any number (including zero) base classes. Use like this:
+ *
+ * DEFINE_CLASSN(foo, foo_class, foo_methods, sizeof(foo_softc)[,
+ *                        bar[, baz[, foobar]]]);
+ */
+#define DEFINE_CLASSN(_name, _classvar, _methods, _size, ...)		\
+	PUBLIC_DEFINE_CLASSN(_name, _classvar, _methods, _size, __VA_ARGS)
+
+/*
+ * Define a public class inheriting any number (including zero) base
+ * classes. Use like this:
+ *
+ * PUBLIC_DEFINE_CLASSN(foo, foo_class, foo_methods, sizeof(foo_softc)[,
+ *                        bar[, baz[, foobar]]]);
+ */
+#define PUBLIC_DEFINE_CLASSN(_name, _classvar, _methods, _size, ...)	\
+									\
+__VA_OPT__(static kobj_class_t _name ## _baseclasses[] = {		\
+	__DEFINE_CLASSN_BASE_EXPANDER(__VA_ARGS__), NULL });		\
+struct kobj_class _classvar = {						\
+	.name = #_name,							\
+	.methods = _methods,						\
+	.size = _size,							\
+	__VA_OPT__(.baseclasses = _name ## _baseclasses,)		\
 }
 
+/*
+ * Define a private class inheriting any number (including zero) base
+ * classes. Use like this:
+ *
+ * PRIVATE_DEFINE_CLASSN(foo, foo_class, foo_methods, sizeof(foo_softc)[,
+ *                        bar[, baz[, foobar]]]);
+ */
+#define PRIVATE_DEFINE_CLASSN(_name, _classvar, _methods, _size, ...)	\
+									\
+__VA_OPT__(static kobj_class_t _name ## _baseclasses[] = {		\
+	__DEFINE_CLASSN_BASE_EXPANDER(__VA_ARGS__), NULL });		\
+static struct kobj_class _classvar = {					\
+	.name = #_name,							\
+	.methods = _methods,						\
+	.size = _size,							\
+	__VA_OPT__(.baseclasses = _name ## _baseclasses,)		\
+}
+
+/* Helper macros for the above, adding ampersands to parent class names */
+#define __DEFINE_CLASSN_BASE_EXPANDER(_base, ...)			\
+	&_base __VA_OPT__(, ___DEFINE_CLASSN_BASE_EXPANDER(__VA_ARGS__))
+
+#define ___DEFINE_CLASSN_BASE_EXPANDER(_base, ...)			\
+	&_base __VA_OPT__(, __DEFINE_CLASSN_BASE_EXPANDER(__VA_ARGS__))
+
 /*
  * Compile the method table in a class.
  */