In the unload target, check that the module is loaded first.

Add a reload target which unloads and then loads the module.

sys/conf/kmod.mk

@@ -28,6 +28,9 @@
 #
 # KMODUNLOAD	Command to unload a kernel module [/sbin/kldunload]
 #
+# KMODISLOADED	Command to check whether a kernel module is
+#		loaded [/sbin/kldstat -q -n]
+#
 # PROG		The name of the kernel module to build.
 #		If not supplied, ${KMOD}.ko is used.
 #
@@ -56,10 +59,14 @@
 # 	unload:
 #		Unload a module.
 #
+#	reload:
+#		Unload if loaded, then load.
+#
 
 AWK?=		awk
 KMODLOAD?=	/sbin/kldload
 KMODUNLOAD?=	/sbin/kldunload
+KMODISLOADED?=	/sbin/kldstat -q -n
 OBJCOPY?=	objcopy
 
 .include <bsd.init.mk>
@@ -325,7 +332,11 @@ load: ${PROG}
 
 .if !target(unload)
 unload:
-	${KMODUNLOAD} -v ${PROG}
+	if ${KMODISLOADED} ${PROG} ; then ${KMODUNLOAD} -v ${PROG} ; fi
+.endif
+
+.if !target(reload)
+reload: unload load
 .endif
 
 .if defined(KERNBUILDDIR)