diff --git a/src/emu/bay.h b/src/emu/bay.h
index 9f9770a..414815e 100644
--- a/src/emu/bay.h
+++ b/src/emu/bay.h
@@ -58,11 +58,12 @@ struct bay {
 	struct bay_chan *dirty;
 };
 
-void bay_init(struct bay *bay);
-int bay_register(struct bay *bay, struct chan *chan);
-int bay_remove(struct bay *bay, struct chan *chan);
-struct chan *bay_find(struct bay *bay, const char *name);
-int bay_add_cb(struct bay *bay, enum bay_cb_type type, struct chan *chan, bay_cb_func_t func, void *arg);
-int bay_propagate(struct bay *bay);
+        void bay_init(struct bay *bay);
+USE_RET int bay_register(struct bay *bay, struct chan *chan);
+USE_RET int bay_remove(struct bay *bay, struct chan *chan);
+USE_RET struct chan *bay_find(struct bay *bay, const char *name);
+USE_RET int bay_add_cb(struct bay *bay, enum bay_cb_type type,
+		struct chan *chan, bay_cb_func_t func, void *arg);
+USE_RET int bay_propagate(struct bay *bay);
 
 #endif /* BAY_H */
diff --git a/src/emu/chan.h b/src/emu/chan.h
index 2c84bbd..02705c9 100644
--- a/src/emu/chan.h
+++ b/src/emu/chan.h
@@ -19,6 +19,7 @@ enum chan_type {
 enum chan_prop {
 	CHAN_DIRTY_WRITE = 0,
 	CHAN_DUPLICATES,
+	CHAN_ROW,
 	CHAN_MAXPROP,
 };
 
@@ -47,22 +48,15 @@ struct chan {
 	void *dirty_arg;
 };
 
-//int chan_enable(struct chan *chan);
-//int chan_disable(struct chan *chan);
-//int chan_is_enabled(const struct chan *chan);
-
-void chan_init(struct chan *chan, enum chan_type type, const char *name);
-int chan_set(struct chan *chan, struct value value);
-int chan_push(struct chan *chan, struct value value);
-int chan_pop(struct chan *chan, struct value expected);
-int chan_read(struct chan *chan, struct value *value);
-enum chan_type chan_get_type(struct chan *chan);
-int chan_flush(struct chan *chan);
-
-void chan_prop_set(struct chan *chan, enum chan_prop prop, int value);
-int chan_prop_get(struct chan *chan, enum chan_prop prop);
-
-/* Called when it becomes dirty */
-void chan_set_dirty_cb(struct chan *chan, chan_cb_t func, void *arg);
+        void chan_init(struct chan *chan, enum chan_type type, const char *name);
+USE_RET int chan_set(struct chan *chan, struct value value);
+USE_RET int chan_push(struct chan *chan, struct value value);
+USE_RET int chan_pop(struct chan *chan, struct value expected);
+USE_RET int chan_read(struct chan *chan, struct value *value);
+USE_RET enum chan_type chan_get_type(struct chan *chan);
+USE_RET int chan_flush(struct chan *chan);
+        void chan_prop_set(struct chan *chan, enum chan_prop prop, int value);
+USE_RET int chan_prop_get(struct chan *chan, enum chan_prop prop);
+        void chan_set_dirty_cb(struct chan *chan, chan_cb_t func, void *arg);
 
 #endif /* CHAN_H */
diff --git a/src/emu/mux.h b/src/emu/mux.h
index f85597b..42e3596 100644
--- a/src/emu/mux.h
+++ b/src/emu/mux.h
@@ -30,20 +30,20 @@ void mux_input_init(struct mux_input *mux,
 		struct value key,
 		struct chan *chan);
 
-int mux_init(struct mux *mux,
+USE_RET int mux_init(struct mux *mux,
 		struct bay *bay,
 		struct chan *select,
 		struct chan *output,
 		mux_select_func_t select_func);
 
-struct mux_input *mux_find_input(struct mux *mux,
+USE_RET struct mux_input *mux_find_input(struct mux *mux,
 		struct value key);
 
-int mux_add_input(struct mux *mux,
+USE_RET int mux_add_input(struct mux *mux,
 		struct value key,
 		struct chan *input);
 
-int mux_register(struct mux *mux,
+USE_RET int mux_register(struct mux *mux,
 		struct bay *bay);
 
 #endif /* MUX_H */
diff --git a/test/unit/mux.c b/test/unit/mux.c
index 504e09c..88c4e52 100644
--- a/test/unit/mux.c
+++ b/test/unit/mux.c
@@ -242,8 +242,10 @@ main(void)
 	if (mux_init(&mux, &bay, &select, &output, NULL) != 0)
 		die("mux_init failed\n");
 
-	for (int i = 0; i < N; i++)
-		mux_add_input(&mux, value_int64(i), &inputs[i]);
+	for (int i = 0; i < N; i++) {
+		if (mux_add_input(&mux, value_int64(i), &inputs[i]) != 0)
+			die("mux_add_input failed\n");
+	}
 
 	/* Write something to the input channels */
 	for (int i = 0; i < N; i++) {