diff --git a/virtio-snd.c b/virtio-snd.c
index 6752756..a3537a8 100644
--- a/virtio-snd.c
+++ b/virtio-snd.c
@@ -168,6 +168,7 @@ typedef struct {
     uint32_t jacks;
     uint32_t streams;
     uint32_t chmaps;
+    uint32_t controls;
 } virtio_snd_config_t;
 
 /* VirtIO sound common header */
@@ -555,6 +556,7 @@ static void virtio_snd_cb(struct CNFADriver *dev,
                           int framesp,
                           int framesr)
 {
+    (void) in; /* reversed for future recording use */
 #if 0
     /* TODO: apply lock on guest_playing */
     vsnd_stream_sel_t *v_ptr = (vsnd_stream_sel_t *) dev->opaque;
@@ -790,7 +792,7 @@ static int virtio_snd_tx_desc_handler(virtio_snd_state_t *vsnd,
     // pthread_mutex_unlock(&virtio_snd_mutex);
 
     /* TODO: remove sleep once find the root cause of infinite loop in TX. */
-    sleep(1);
+    // sleep(1);
 
     return 0;
 }
@@ -1074,6 +1076,8 @@ bool virtio_snd_init(virtio_snd_state_t *vsnd)
     PRIV(vsnd)->jacks = 1;
     PRIV(vsnd)->streams = 1;
     PRIV(vsnd)->chmaps = 1;
+    PRIV(vsnd)->controls =
+        0; /* virtio-snd device does not support control elements */
 
     return true;
 }