impl-port: only send latency param when supported

Check if the port has latency param and only try to set the
latency param when it appears available. This avoids sending unknown
latency params to an old client and erroring out.

src/pipewire/impl-port.c

@@ -375,6 +375,8 @@ static int process_latency_param(void *data, int seq,
 	this->latency[latency.direction] = latency;
 	if (latency.direction == this->direction)
 		pw_impl_port_emit_latency_changed(this);
+
+	this->have_latency_param = true;
 	return 0;
 }
 
@@ -1292,7 +1294,7 @@ int pw_impl_port_for_each_link(struct pw_impl_port *port,
 	return res;
 }
 
-static void port_set_latency(struct pw_impl_port *port, struct spa_latency_info *latency)
+static int port_set_latency(struct pw_impl_port *port, struct spa_latency_info *latency)
 {
 	struct spa_latency_info *current;
 	struct spa_pod *param;
@@ -1302,7 +1304,7 @@ static void port_set_latency(struct pw_impl_port *port, struct spa_latency_info
 	current = &port->latency[latency->direction];
 
 	if (spa_latency_info_compare(current, latency) == 0)
-		return;
+		return 0;
 
 	*current = *latency;
 
@@ -1312,9 +1314,12 @@ static void port_set_latency(struct pw_impl_port *port, struct spa_latency_info
 			latency->min_rate, latency->max_rate,
 			latency->min_ns, latency->max_ns);
 
+	if (!port->have_latency_param)
+		return 0;
+
 	spa_pod_builder_init(&b, buffer, sizeof(buffer));
 	param = spa_latency_build(&b, SPA_PARAM_Latency, latency);
-	pw_impl_port_set_param(port, SPA_PARAM_Latency, 0, param);
+	return pw_impl_port_set_param(port, SPA_PARAM_Latency, 0, param);
 }
 
 int pw_impl_port_recalc_latency(struct pw_impl_port *port)

src/pipewire/private.h

@@ -793,6 +793,7 @@ struct pw_impl_port {
 	unsigned int added:1;
 
 	struct spa_latency_info latency[2];	/**< latencies */
+	unsigned int have_latency_param:1;
 
 	void *owner_data;		/**< extra owner data */
 	void *user_data;                /**< extra user data */