node: add flag to always assign a driver to a node

Add flag to always assign a node to a driver. This makes sure that
even when the node is not linked to anything, it will still be
scheduled by an active driver. This is needed for JACK support.

spa/include/spa/node/node.h

@@ -653,8 +653,11 @@ struct spa_node_methods {
 
 /** node keys */
 #define SPA_KEY_NODE_NAME		"node.name"		/**< a node name */
-#define SPA_KEY_NODE_DRIVER		"node.driver"		/**< the node can be a driver */
 #define SPA_KEY_NODE_LATENCY		"node.latency"		/**< the requested node latency */
+
+#define SPA_KEY_NODE_DRIVER		"node.driver"		/**< the node can be a driver */
+#define SPA_KEY_NODE_ALWAYS_PROCESS	"node.always-process"	/**< call the process function even if
+								  *  not linked. */
 #define SPA_KEY_NODE_PAUSE_ON_IDLE	"node.pause-on-idle"	/**< if the node should be paused
 								  *  immediately when idle. */
 

src/pipewire/core.c

@@ -1101,22 +1101,63 @@ static int collect_nodes(struct pw_node *driver)
 
 int pw_core_recalc_graph(struct pw_core *core)
 {
-	struct pw_node *n, *s;
+	struct pw_node *n, *s, *target;
 
+	/* start from all drivers and group all nodes that are linked
+	 * to it. Some nodes are not (yet) linked to anything and they
+	 * will end up 'unassigned' to a master. Other nodes are master
+	 * and if they have active slaves, we can use them to schedule
+	 * the unassigned nodes. */
+	target = NULL;
 	spa_list_for_each(n, &core->driver_list, driver_link) {
-		if (!n->visited)
+		uint32_t active_slaves;
+
+		if (n->active && !n->visited)
 			collect_nodes(n);
+
+		/* from now on we are only interested in nodes that are
+		 * a master. We're going to count the number of slaves it
+		 * has. */
+		if (!n->master)
+			continue;
+
+		active_slaves = 0;
+		spa_list_for_each(s, &n->slave_list, slave_link) {
+			pw_log_info(NAME" %p: driver %p: slave %p %s: %d",
+					core, n, s, s->name, s->active);
+			if (s != n && s->active)
+				active_slaves++;
+		}
+		pw_log_info(NAME" %p: driver %p active slaves %d",
+				core, n, active_slaves);
+
+		/* if the master has active slaves, it is a target for our
+		 * unassigned nodes */
+		if (active_slaves > 0) {
+			if (target == NULL)
+				target = n;
+		}
 	}
 
+	/* now go through all available nodes. The ones we didn't visit
+	 * in collect_nodes() are not linked to any master. We assign them
+	 * to an active master */
 	spa_list_for_each(n, &core->node_list, link) {
 		if (!n->visited) {
 			pw_log_info(NAME" %p: unassigned node %p: '%s' %d", core,
 					n, n->name, n->active);
+			if (!n->want_driver)
 				pw_node_set_driver(n, NULL);
+			else {
+				pw_node_set_driver(n, target);
+				pw_node_set_state(n, target && n->active ?
+						PW_NODE_STATE_RUNNING : PW_NODE_STATE_IDLE);
+			}
 		}
 		n->visited = false;
 	}
 
+	/* debug only here to list all masters and their slaves */
 	spa_list_for_each(n, &core->driver_list, driver_link) {
 		if (!n->master)
 			continue;

src/pipewire/keys.h

@@ -121,6 +121,7 @@ extern "C" {
 #define PW_KEY_NODE_LATENCY		"node.latency"		/**< the requested latency of the node as
 								  *  a fraction. Ex: 128/48000 */
 #define PW_KEY_NODE_DONT_RECONNECT	"node.dont-reconnect"	/**< don't reconnect this node */
+#define PW_KEY_NODE_ALWAYS_PROCESS	"node.always-process"	/**< process even when unlinked */
 #define PW_KEY_NODE_PAUSE_ON_IDLE	"node.pause-on-idle"	/**< pause the node when idle */
 #define PW_KEY_NODE_DRIVER		"node.driver"		/**< node can drive the graph */
 #define PW_KEY_NODE_STREAM		"node.stream"		/**< node is a stream, the server side should

src/pipewire/node.c

@@ -601,6 +601,8 @@ int pw_node_register(struct pw_node *this,
 	spa_list_for_each(port, &this->output_ports, link)
 		pw_port_register(port, NULL);
 
+	pw_core_recalc_graph(core);
+
 	return 0;
 
 error_existed:
@@ -706,6 +708,11 @@ static void check_properties(struct pw_node *node)
 	else
 		driver = false;
 
+	if ((str = pw_properties_get(node->properties, PW_KEY_NODE_ALWAYS_PROCESS)))
+		node->want_driver = pw_properties_parse_bool(str);
+	else
+		node->want_driver = false;
+
 	if (node->driver != driver) {
 		pw_log_info(NAME" %p: driver %d -> %d", node, node->driver, driver);
 		node->driver = driver;

src/pipewire/private.h

@@ -419,6 +419,7 @@ struct pw_node {
 	unsigned int master:1;		/**< a master node is one of the driver nodes that
 					  *  is selected to drive the graph */
 	unsigned int visited:1;		/**< for sorting */
+	unsigned int want_driver:1;	/**< this node wants to be assigned to a driver */
 
 	uint32_t port_user_data_size;	/**< extra size for port user data */