bluez5: driver should produce buffers before ready

The graph cycle goes: driver timeout -> process output nodes -> process
driver node.  Hence, driver should produce buffers in the timeout,
otherwise there's one quantum extra latency.

Make the bluez5 media/sco sources as drivers put a buffer to io before
indicating ready, and as follower do it in process. Also make checks if
io == NULL, and don't set io->status to HAVE_DATA unless there really is
a buffer ready.

spa/plugins/bluez5/media-source.c

@@ -568,13 +568,14 @@ static int setup_matching(struct impl *this)
 	return 0;
 }
 
+static int produce_buffer(struct impl *this);
+
 static void media_on_timeout(struct spa_source *source)
 {
 	struct impl *this = source->data;
 	struct port *port = &this->port;
 	uint64_t exp, duration;
 	uint32_t rate;
-	struct spa_io_buffers *io = port->io;
 	uint64_t prev_time, now_time;
 
 	if (this->transport == NULL)
@@ -609,8 +610,11 @@ static void media_on_timeout(struct spa_source *source)
 		this->clock->next_nsec = this->next_time;
 	}
 
-	spa_log_trace(this->log, "%p: %d", this, io->status);
+	if (port->io) {
-	io->status = SPA_STATUS_HAVE_DATA;
+		int status = produce_buffer(this);
+		spa_log_trace(this->log, "%p: io:%d status:%d", this, port->io->status, status);
+	}
+
 	spa_node_call_ready(&this->callbacks, SPA_STATUS_HAVE_DATA);
 
 	set_timeout(this, this->next_time);
@@ -1343,12 +1347,50 @@ static void process_buffering(struct impl *this)
 	}
 }
 
+static int produce_buffer(struct impl *this)
+{
+	struct buffer *buffer;
+	struct port *port = &this->port;
+	struct spa_io_buffers *io = port->io;
+
+	if (io == NULL)
+		return -EIO;
+
+	/* Return if we already have a buffer */
+	if (io->status == SPA_STATUS_HAVE_DATA)
+		return SPA_STATUS_HAVE_DATA;
+
+	/* Recycle */
+	if (io->buffer_id < port->n_buffers) {
+		recycle_buffer(this, port, io->buffer_id);
+		io->buffer_id = SPA_ID_INVALID;
+	}
+
+	/* Handle buffering */
+	process_buffering(this);
+
+	/* Return if there are no buffers ready to be processed */
+	if (spa_list_is_empty(&port->ready))
+		return SPA_STATUS_OK;
+
+	/* Get the new buffer from the ready list */
+	buffer = spa_list_first(&port->ready, struct buffer, link);
+	spa_list_remove(&buffer->link);
+	buffer->outstanding = true;
+
+	/* Set the new buffer in IO */
+	io->buffer_id = buffer->id;
+	io->status = SPA_STATUS_HAVE_DATA;
+
+	/* Notify we have a buffer ready to be processed */
+	return SPA_STATUS_HAVE_DATA;
+}
+
 static int impl_node_process(void *object)
 {
 	struct impl *this = object;
 	struct port *port;
 	struct spa_io_buffers *io;
-	struct buffer *buffer;
 
 	spa_return_val_if_fail(this != NULL, -EINVAL);
 
@@ -1368,24 +1410,11 @@ static int impl_node_process(void *object)
 		io->buffer_id = SPA_ID_INVALID;
 	}
 
-	/* Handle buffering delay */
+	/* Follower produces buffers here, driver in timeout */
-	process_buffering(this);
+	if (this->following)
-
+		return produce_buffer(this);
-	/* Return if there are no buffers ready to be processed */
+	else
-	if (spa_list_is_empty(&port->ready))
 		return SPA_STATUS_OK;
-
-	/* Get the new buffer from the ready list */
-	buffer = spa_list_first(&port->ready, struct buffer, link);
-	spa_list_remove(&buffer->link);
-	buffer->outstanding = true;
-
-	/* Set the new buffer in IO */
-	io->buffer_id = buffer->id;
-	io->status = SPA_STATUS_HAVE_DATA;
-
-	/* Notify we have a buffer ready to be processed */
-	return SPA_STATUS_HAVE_DATA;
 }
 
 static const struct spa_node_methods impl_node = {

spa/plugins/bluez5/sco-source.c

@@ -591,13 +591,14 @@ static int setup_matching(struct impl *this)
 	return 0;
 }
 
+static int produce_buffer(struct impl *this);
+
 static void sco_on_timeout(struct spa_source *source)
 {
 	struct impl *this = source->data;
 	struct port *port = &this->port;
 	uint64_t exp, duration;
 	uint32_t rate;
-	struct spa_io_buffers *io = port->io;
 	uint64_t prev_time, now_time;
 
 	if (this->transport == NULL)
@@ -632,8 +633,11 @@ static void sco_on_timeout(struct spa_source *source)
 		this->clock->next_nsec = this->next_time;
 	}
 
-	spa_log_trace(this->log, "%p: %d", this, io->status);
+	if (port->io) {
-	io->status = SPA_STATUS_HAVE_DATA;
+		int status = produce_buffer(this);
+		spa_log_trace(this->log, "%p: io:%d status:%d", this, port->io->status, status);
+	}
+
 	spa_node_call_ready(&this->callbacks, SPA_STATUS_HAVE_DATA);
 
 	set_timeout(this, this->next_time);
@@ -1286,17 +1290,13 @@ static void process_buffering(struct impl *this)
 	}
 }
 
-static int impl_node_process(void *object)
+static int produce_buffer(struct impl *this)
 {
-	struct impl *this = object;
-	struct port *port;
-	struct spa_io_buffers *io;
 	struct buffer *buffer;
+	struct port *port = &this->port;
+	struct spa_io_buffers *io = port->io;
 
-	spa_return_val_if_fail(this != NULL, -EINVAL);
+	if (io == NULL)
-
-	port = &this->port;
-	if ((io = port->io) == NULL)
 		return -EIO;
 
 	/* Return if we already have a buffer */
@@ -1309,7 +1309,7 @@ static int impl_node_process(void *object)
 		io->buffer_id = SPA_ID_INVALID;
 	}
 
-	/* Produce data */
+	/* Handle buffering */
 	process_buffering(this);
 
 	/* Return if there are no buffers ready to be processed */
@@ -1329,6 +1329,35 @@ static int impl_node_process(void *object)
 	return SPA_STATUS_HAVE_DATA;
 }
 
+static int impl_node_process(void *object)
+{
+	struct impl *this = object;
+	struct port *port;
+	struct spa_io_buffers *io;
+
+	spa_return_val_if_fail(this != NULL, -EINVAL);
+
+	port = &this->port;
+	if ((io = port->io) == NULL)
+		return -EIO;
+
+	/* Return if we already have a buffer */
+	if (io->status == SPA_STATUS_HAVE_DATA)
+		return SPA_STATUS_HAVE_DATA;
+
+	/* Recycle */
+	if (io->buffer_id < port->n_buffers) {
+		recycle_buffer(this, port, io->buffer_id);
+		io->buffer_id = SPA_ID_INVALID;
+	}
+
+	/* Follower produces buffers here, driver in timeout */
+	if (this->following)
+		return produce_buffer(this);
+	else
+		return SPA_STATUS_OK;
+}
+
 static const struct spa_node_methods impl_node = {
 	SPA_VERSION_NODE_METHODS,
 	.add_listener = impl_node_add_listener,