Add ring buffer implementation hint

Author: Cuda-Chen

virtio-snd.c

@@ -772,18 +772,15 @@ static int virtio_snd_tx_desc_handler(virtio_snd_state_t *vsnd,
             goto early_continue;
         }
 
-        /*frame = (virtio_snd_pcm_frame_t *) malloc(sizeof(*frame));
-        void *buf = (void *) (base + addr);
-        frame->buf = (void *) malloc(sizeof(frame->buf) * len);
-        memcpy(frame->buf, buf, len);
-        queue_push(&frame->q, frame_q);*/
+        /* TODO: ring buffer implementation here */
         ret_len += len;
 
     early_continue:
         idx++;
     }
 
     /* Tear down the descriptor list and free space. */
+    /* TODO: remove this part as we are going to use ring buffer */
     idx = 0;
     virtq_desc_queue_node_t *tmp = NULL;
     queue_for_each_entry_safe(node, tmp, &q, q)