On Wed, Apr 28, 2021 at 03:36:02PM +0000, Liam Howlett wrote:

+enum maple_type {
+	maple_dense,
+	maple_leaf_64,
+	maple_range_64,
+	maple_arange_64,
+};

+static inline unsigned long *ma_pivots(struct maple_node *node,
+					   enum maple_type type)
+{
+	switch (type) {
+	case maple_arange_64:
+		return node->ma64.pivot;
+	case maple_range_64:
+	case maple_leaf_64:
+		return node->mr64.pivot;
+	case maple_dense:
+	default:
+		return NULL;
+	}
+}

+static inline unsigned long *ma_gaps(struct maple_node *node,
+				     enum maple_type type)
+{
+	switch (type) {
+	case maple_arange_64:
+		return node->ma64.gap;
+	case maple_range_64:
+	case maple_leaf_64:
+	case maple_dense:
+	default:
+		return NULL;
+	}
+}

+static inline unsigned long mte_pivot(const struct maple_enode *mn,
+				 unsigned char piv)
+{
+	struct maple_node *node = mte_to_node(mn);
+
+	switch (mte_node_type(mn)) {
+	case maple_arange_64:
+		return node->ma64.pivot[piv];
+	case maple_range_64:
+	case maple_leaf_64:
+		return node->mr64.pivot[piv];
+	case maple_dense:
+	default:
+		return 0;
+	}
+}

I would suggest removing the default: case. Without it the cases are
complete and the compiler should not complain. Then if you extend the
enum and forget to add a case, the switch is no longer complete and will
trigger a warning, forcing you to update it (hopefully correct).

If you have the default, you'll not get a warning and it'll do whatever.