Release CNFA driver in pcm_release

Author: Cuda-Chen

virtio-snd.c

@@ -378,6 +378,7 @@ static void virtio_snd_read_pcm_prepare(struct virtq_desc *vq_desc,
 {
     virtio_snd_pcm_hdr_t *request = query;
     uint32_t stream_id = request->stream_id;
+    vsnd_props[stream_id].pp.hdr.hdr.code = VIRTIO_SND_R_PCM_PREPARE;
     vsnd_props[stream_id].audio_host = CNFAInit(
         NULL, "semu-virtio-snd", virtio_snd_cb, 44100, 0, 1, 0,
         vsnd_props[stream_id].pp.buffer_bytes, NULL, NULL, &guest_playing);
@@ -416,7 +417,14 @@ static void virtio_snd_read_pcm_stop(struct virtq_desc *vq_desc,
 static void virtio_snd_read_pcm_release(struct virtq_desc *vq_desc,
                                         const virtio_snd_query_info_t *query)
 {
-    /* TODO: let application to set stream_id at will */
+    /* Control the callback to stop playing */
+    /* TODO: add lock to avoid race condition */
+    guest_playing = false;
+
+    virtio_snd_pcm_hdr_t *request = query;
+    uint32_t stream_id = request->stream_id;
+    vsnd_props[stream_id].pp.hdr.hdr.code = VIRTIO_SND_R_PCM_RELEASE;
+    CNFAClose(vsnd_props[stream_id].audio_host);
 
     fprintf(stderr, "virtio_snd_read_pcm_release\n");
 }