Add buffer queue prototype

Author: Cuda-Chen

virtio-snd.c

@@ -315,6 +315,7 @@ typedef struct {
     virtio_snd_ring_buffer_t ring;
     // PCM frame doubly-ended queue
     vsnd_buf_queue_node_t buf;
+    struct list_head buf_queue_head;
 
     // playback control
     vsnd_stream_sel_t v;
@@ -560,6 +561,7 @@ static void virtio_snd_read_pcm_prepare(const virtio_snd_pcm_hdr_t *query,
     pthread_mutex_init(&props->ring.lock, NULL);
     pthread_cond_init(&props->ring.readable, NULL);
     pthread_cond_init(&props->ring.writable, NULL);
+    INIT_LIST_HEAD(&props->buf_queue_head);
 
     *plen = 0;
     fprintf(stderr, "virtio_snd_read_pcm_prepare\n");
@@ -639,6 +641,13 @@ static void virtio_snd_read_pcm_release(const virtio_snd_pcm_hdr_t *query,
     pthread_mutex_destroy(&props->ring.lock);
     pthread_cond_destroy(&props->ring.readable);
     pthread_cond_destroy(&props->ring.writable);
+    /* Tear down the PCM buffer queue */
+    vsnd_buf_queue_node_t *tmp = NULL;
+    vsnd_buf_queue_node_t *node;
+    list_for_each_entry_safe (node, tmp, &props->buf_queue_head, q) {
+        list_del(&node->q);
+        free(node);
+    }
 
     CNFAClose(props->audio_host);
     fprintf(stderr, "pass CNFAclose\n");
@@ -896,6 +905,12 @@ static void __virtio_snd_frame_enqueue(void *payload,
     /* Update prod_tail */
     props->ring.prod.tail = prod_next;
 
+    /* Add to queue */
+    vsnd_buf_queue_node_t *node = malloc(sizeof(*node));
+    node->addr = (uint32_t) payload;
+    node->len = n;
+    list_push(&node->q, &props->buf_queue_head);
+
     uint32_t period_bytes = props->pp.period_bytes;
     if (prod_next - cons_tail >= period_bytes) {
         fprintf(stderr,