select.c: Clarify osmo_fd_unregister() can only be called on registered osmo_fds
Change-Id: I5e397e121f2fe2254c7f4b474e6eefd7aebe7a83
diff --git a/src/core/select.c b/src/core/select.c
index 584de24..67b0fd3 100644
--- a/src/core/select.c
+++ b/src/core/select.c
@@ -212,6 +212,7 @@
/*! Unregister a file descriptor from select loop abstraction
* \param[in] fd osmocom file descriptor to be unregistered
*
+ * Caller is responsible for ensuring the fd is really registered before calling this API.
* This function must be called before changing the value of the fd field in
* the struct osmo_fd.
*/