buffer_tree.c: Add documentation of btr_parent().

This function was introduced in commit 37e0dfe7 (check_wav: Ask parent
nodes before falling back to defaults) without documentation.

diff --git a/buffer_tree.c b/buffer_tree.c
index f0a7b224f9fad39fd8036d37eedbf619e3ca585b..fd0a59cad58c0027e3911b08eb5f0bd20a176ed5 100644 (file)
--- a/buffer_tree.c
+++ b/buffer_tree.c
@@ -1230,6 +1230,16 @@ void btr_get_node_start(struct btr_node *btrn, struct timeval *tv)
        *tv = btrn->start;
 }
 
+/**
+ * Get the parent node of a buffer tree node.
+ *
+ * \param btrn The node whose parent should be returned.
+ *
+ * \a btrn must not be \p NULL.
+ *
+ * \return The parent of \a btrn, or \p NULL if \a btrn is the
+ * root node of the buffer tree.
+ */
 struct btr_node *btr_parent(struct btr_node *btrn)
 {
        return btrn->parent;