From 495dbc1aa65ceeb5fc1f5e0867aa00fa67568872 Mon Sep 17 00:00:00 2001
From: Bjarne von Horn <vh@igh.de>
Date: Thu, 6 Jun 2024 13:55:40 +0200
Subject: [PATCH] Fix return value for ecrt_master_send_ext().

---
 include/ecrt.h  | 1 +
 master/master.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/ecrt.h b/include/ecrt.h
index 00e2eb8c..0d545dc5 100644
--- a/include/ecrt.h
+++ b/include/ecrt.h
@@ -1110,6 +1110,7 @@ EC_PUBLIC_API int ecrt_master_receive(
  * This method has to be called in the send callback function passed via
  * ecrt_master_callbacks() to allow the sending of non-application datagrams.
  * \return Zero on success, otherwise negative error code.
+ * \retval -EAGAIN Lock could not be acquired, try again later.
  */
 int ecrt_master_send_ext(
         ec_master_t *master /**< EtherCAT master. */
diff --git a/master/master.c b/master/master.c
index 5b320d92..cda6eda9 100644
--- a/master/master.c
+++ b/master/master.c
@@ -2534,7 +2534,7 @@ int ecrt_master_send_ext(ec_master_t *master)
     ec_datagram_t *datagram, *next;
 
     if (down_trylock(&master->ext_queue_sem))
-        return;
+        return -EAGAIN;
 
     list_for_each_entry_safe(datagram, next, &master->ext_datagram_queue,
             ext_queue) {