diff --git a/src/v4l2.c b/src/v4l2.c
index 9e2ce8b..27d9e61 100644
--- a/src/v4l2.c
+++ b/src/v4l2.c
@@ -476,12 +476,35 @@ int v4l2_set_controls(int video_fd, int request_fd,
 		      struct v4l2_ext_control *control_array,
 		      unsigned int num_controls)
 {
+	struct v4l2_ext_controls controls;
 	int rc;
 
-	rc = v4l2_ioctl_controls(video_fd, request_fd, VIDIOC_S_EXT_CTRLS,
-				 control_array, num_controls);
+	memset(&controls, 0, sizeof(controls));
+	controls.controls = control_array;
+	controls.count = num_controls;
+	if (request_fd >= 0) {
+		controls.which = V4L2_CTRL_WHICH_REQUEST_VAL;
+		controls.request_fd = request_fd;
+	}
+
+	rc = ioctl(video_fd, VIDIOC_S_EXT_CTRLS, &controls);
 	if (rc < 0) {
-		request_log("Unable to set control(s): %s\n", strerror(errno));
+		/* error_idx is the index of the first failing control;
+		 * if it equals count, the ioctl itself failed (not a
+		 * specific control payload).  Useful for triaging
+		 * which V4L2_CID_STATELESS_* the kernel rejected. */
+		if (controls.error_idx < num_controls)
+			request_log("Unable to set control(s): %s "
+				    "(error_idx=%u/%u failing_ctrl_id=0x%x size=%u)\n",
+				    strerror(errno),
+				    controls.error_idx, controls.count,
+				    control_array[controls.error_idx].id,
+				    control_array[controls.error_idx].size);
+		else
+			request_log("Unable to set control(s): %s "
+				    "(error_idx=%u/%u ioctl-level)\n",
+				    strerror(errno),
+				    controls.error_idx, controls.count);
 		return -1;
 	}