Update doxygen annotations in libosmocore
This adds and improves doxygen API descriptions all over libosmocore,
reducing the 'white spots' that don't have any documentation.
diff --git a/src/write_queue.c b/src/write_queue.c
index 9a8b05c..3e488ae 100644
--- a/src/write_queue.c
+++ b/src/write_queue.c
@@ -33,6 +33,7 @@
/*! \brief Select loop function for write queue handling
* \param[in] fd osmocom file descriptor
* \param[in] what bit-mask of events that have happened
+ * \returns 0 on success; negative on error
*
* This function is provided so that it can be registered with the
* select loop abstraction code (\ref osmo_fd::cb).
@@ -99,6 +100,7 @@
/*! \brief Enqueue a new \ref msgb into a write queue
* \param[in] queue Write queue to be used
* \param[in] data to-be-enqueued message buffer
+ * \returns 0 on success; negative on error
*/
int osmo_wqueue_enqueue(struct osmo_wqueue *queue, struct msgb *data)
{