regmap: rbtree: Factor out node allocation

In preparation for being slightly smarter about how we allocate memory
factor out the node allocation.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regcache-rbtree.c

@@ -304,6 +304,27 @@ static int regcache_rbtree_insert_to_block(struct regmap *map,
 	return 0;
 }
 
+static struct regcache_rbtree_node *
+regcache_rbtree_node_alloc(struct regmap *map, unsigned int reg)
+{
+	struct regcache_rbtree_node *rbnode;
+
+	rbnode = kzalloc(sizeof(*rbnode), GFP_KERNEL);
+	if (!rbnode)
+		return NULL;
+
+	rbnode->blklen = sizeof(*rbnode);
+	rbnode->base_reg = reg;
+	rbnode->block = kmalloc(rbnode->blklen * map->cache_word_size,
+				GFP_KERNEL);
+	if (!rbnode->block) {
+		kfree(rbnode);
+		return NULL;
+	}
+
+	return rbnode;
+}
+
 static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
 				 unsigned int value)
 {
@@ -354,23 +375,15 @@ static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
 				return 0;
 			}
 		}
-		/* we did not manage to find a place to insert it in an existing
-		 * block so create a new rbnode with a single register in its block.
-		 * This block will get populated further if any other adjacent
-		 * registers get modified in the future.
+
+		/* We did not manage to find a place to insert it in
+		 * an existing block so create a new rbnode.
 		 */
-		rbnode = kzalloc(sizeof *rbnode, GFP_KERNEL);
+		rbnode = regcache_rbtree_node_alloc(map, reg);
 		if (!rbnode)
 			return -ENOMEM;
-		rbnode->blklen = sizeof(*rbnode);
-		rbnode->base_reg = reg;
-		rbnode->block = kmalloc(rbnode->blklen * map->cache_word_size,
-					GFP_KERNEL);
-		if (!rbnode->block) {
-			kfree(rbnode);
-			return -ENOMEM;
-		}
-		regcache_rbtree_set_register(map, rbnode, 0, value);
+		regcache_rbtree_set_register(map, rbnode,
+					     reg - rbnode->base_reg, value);
 		regcache_rbtree_insert(map, &rbtree_ctx->root, rbnode);
 		rbtree_ctx->cached_rbnode = rbnode;
 	}