Index: sys/kern/kern_module.c
===================================================================
--- sys/kern/kern_module.c
+++ sys/kern/kern_module.c
@@ -66,7 +66,7 @@
 static void module_shutdown(void *, int);
 
 static int
-modevent_nop(module_t mod, int what, void *arg)
+modevent_no_unload(module_t mod, int what, void *arg)
 {
 
 	switch(what) {
@@ -79,6 +79,26 @@
 	}
 }
 
+int
+modevent_nop(module_t mod __unused, int type, void *unused __unused)
+{
+	int error;
+
+	switch (type) {
+	case MOD_LOAD:
+	case MOD_QUIESCE:
+	case MOD_UNLOAD:
+	case MOD_SHUTDOWN:
+		error = 0;
+		break;
+	default:
+		error = EOPNOTSUPP;
+		break;
+	}
+
+	return (error);
+}
+
 static void
 module_init(void *arg)
 {
@@ -168,7 +188,7 @@
 	newmod->id = nextid++;
 	newmod->name = (char *)(newmod + 1);
 	strcpy(newmod->name, data->name);
-	newmod->handler = data->evhand ? data->evhand : modevent_nop;
+	newmod->handler = data->evhand ? data->evhand : modevent_no_unload;
 	newmod->arg = data->priv;
 	bzero(&newmod->data, sizeof(newmod->data));
 	TAILQ_INSERT_TAIL(&modules, newmod, link);
Index: sys/sys/module.h
===================================================================
--- sys/sys/module.h
+++ sys/sys/module.h
@@ -52,6 +52,13 @@
 typedef struct module *module_t;
 typedef int (*modeventhand_t)(module_t, int /* modeventtype_t */, void *);
 
+/*
+ * A module can use this to ignore all valid module events.  (In contrast, a
+ * NULL eventhandler prevents module unload with EBUSY, and returns EOPNOTSUPP
+ * for QUIESCE and SHUTDOWN.)
+ */
+int modevent_nop(module_t, int, void *);
+
 /*
  * Struct for registering modules statically via SYSINIT.
  */