sound/pipewire: destroy pipewire streams not destroyed

The PCM command transition prepare->prepare or set_param->prepare
is allowed by the specification. Pipewire, however, creates multiple
streams which are not destroyed when this type of transition happens.
By using this PR, we can ensure that when the prepare function in the
pipewire backend is called multiple times without the release function,
only one pipewire stream is created.

Close rust-vmm#490

Signed-off-by: Dorinda Bassey <dbassey@redhat.com>

vhost-device-sound/src/audio_backends/pipewire.rs

@@ -208,6 +208,15 @@ impl AudioBackend for PwBackend {
 
             let params = &stream_params[stream_id as usize].params;
 
+            if let Some(stream) = stream_hash.get(&stream_id) {
+                if let Err(err) = stream.disconnect() {
+                    log::error!("Stream {} disconnect {}", stream_id, err);
+                    return Err(Error::CouldNotDisconnectStream);
+                }
+                stream_hash.remove(&stream_id);
+                stream_listener.remove(&stream_id);
+            }
+
             let mut pos: [u32; 64] = [SPA_AUDIO_CHANNEL_UNKNOWN; 64];
 
             match params.channels {

vhost-device-sound/src/lib.rs

@@ -183,6 +183,8 @@ pub enum Error {
     StreamWithIdNotFound(u32),
     #[error("Channel number not supported: {0}")]
     ChannelNotSupported(u8),
+    #[error("Could not disconnect stream")]
+    CouldNotDisconnectStream,
 }
 
 impl From<Error> for IoError {