m-log-settings: add module for changing log level at runtime

Pipewire server uses the global "settings" metadata for adjusting its
own log level.

Make it a convention that clients may watch "log.level" in this metadata
with their client id as subject, for setting their own log level
dynamically.

Watch the global "settings" metadata for "log.level" changes for our id.
On changes, set our log level accordingly.

modules/meson.build

@@ -151,6 +151,17 @@ shared_library(
   dependencies : [wp_dep, pipewire_dep],
 )
 
+shared_library(
+  'wireplumber-module-log-settings',
+  [
+    'module-log-settings.c',
+  ],
+  c_args : [common_c_args, '-DG_LOG_DOMAIN="m-log-settings"'],
+  install : true,
+  install_dir : wireplumber_module_dir,
+  dependencies : [wp_dep, pipewire_dep],
+)
+
 if libsystemd_dep.found() or libelogind_dep.found()
   shared_library(
     'wireplumber-module-logind',

modules/module-log-settings.c

@@ -0,0 +1,103 @@
+/* WirePlumber
+ *
+ * Copyright © 2023 Collabora Ltd.
+ * Copyright © 2023 Pauli Virtanen <pav@iki.fi>
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <wp/wp.h>
+#include <errno.h>
+#include <pipewire/pipewire.h>
+#include <pipewire/keys.h>
+
+WP_DEFINE_LOCAL_LOG_TOPIC ("m-log-settings")
+
+struct _WpLogSettingsPlugin
+{
+  WpPlugin parent;
+  WpObjectManager *metadata_om;
+};
+
+G_DECLARE_FINAL_TYPE (WpLogSettingsPlugin, wp_log_settings_plugin,
+                      WP, LOG_SETTINGS_PLUGIN, WpPlugin)
+G_DEFINE_TYPE (WpLogSettingsPlugin, wp_log_settings_plugin, WP_TYPE_PLUGIN)
+
+static void
+wp_log_settings_plugin_init (WpLogSettingsPlugin * self)
+{
+}
+
+static void
+on_metadata_changed (WpMetadata *m, guint32 subject,
+    const gchar *key, const gchar *type, const gchar *value, gpointer d)
+{
+  WpLogSettingsPlugin * self = WP_LOG_SETTINGS_PLUGIN (d);
+  g_autoptr (WpCore) core = wp_object_get_core (WP_OBJECT (self));
+  g_return_if_fail (core);
+
+  if (subject != wp_core_get_own_bound_id (core))
+    return;
+
+  if (spa_streq(key, "log.level"))
+    wp_log_set_global_level (value ? value : "2");
+}
+
+static void
+on_metadata_added (WpObjectManager *om, WpMetadata *metadata, gpointer d)
+{
+  WpLogSettingsPlugin * self = WP_LOG_SETTINGS_PLUGIN (d);
+  g_autoptr (WpCore) core = wp_object_get_core (WP_OBJECT (self));
+  g_return_if_fail (core);
+
+  /* Handle the changed signal */
+  g_signal_connect_object (metadata, "changed",
+      G_CALLBACK (on_metadata_changed), self, 0);
+}
+
+static void
+wp_log_settings_plugin_enable (WpPlugin * plugin, WpTransition * transition)
+{
+  WpLogSettingsPlugin * self = WP_LOG_SETTINGS_PLUGIN (plugin);
+  g_autoptr (WpCore) core = wp_object_get_core (WP_OBJECT (plugin));
+  g_return_if_fail (core);
+
+  /* Create the metadata object manager */
+  self->metadata_om = wp_object_manager_new ();
+  wp_object_manager_add_interest (self->metadata_om, WP_TYPE_METADATA,
+      WP_CONSTRAINT_TYPE_PW_GLOBAL_PROPERTY, "metadata.name", "=s", "settings",
+      NULL);
+  wp_object_manager_request_object_features (self->metadata_om,
+      WP_TYPE_METADATA, WP_OBJECT_FEATURES_ALL);
+  g_signal_connect_object (self->metadata_om, "object-added",
+      G_CALLBACK (on_metadata_added), self, 0);
+  wp_core_install_object_manager (core, self->metadata_om);
+
+  wp_object_update_features (WP_OBJECT (self), WP_PLUGIN_FEATURE_ENABLED, 0);
+}
+
+static void
+wp_log_settings_plugin_disable (WpPlugin * plugin)
+{
+  WpLogSettingsPlugin * self = WP_LOG_SETTINGS_PLUGIN (plugin);
+
+  g_clear_object (&self->metadata_om);
+}
+
+static void
+wp_log_settings_plugin_class_init (WpLogSettingsPluginClass * klass)
+{
+  WpPluginClass *plugin_class = (WpPluginClass *) klass;
+
+  plugin_class->enable = wp_log_settings_plugin_enable;
+  plugin_class->disable = wp_log_settings_plugin_disable;
+}
+
+WP_PLUGIN_EXPORT GObject *
+wireplumber__module_init (WpCore * core, GVariant * args, GError ** error)
+{
+  return G_OBJECT (g_object_new (wp_log_settings_plugin_get_type (),
+          "name", "log-settings",
+          "core", core,
+          NULL));
+}

src/config/wireplumber.conf

@@ -71,6 +71,7 @@ wireplumber.profiles = {
   main = {
     check.no-media-session = required
     support.settings = required
+    support.log-settings = required
     metadata.sm-objects = required
     hardware.audio = required
     hardware.bluetooth = required
@@ -155,6 +156,12 @@ wireplumber.components = [
     provides = support.settings
   }
 
+  ## Log level settings
+  {
+    name = libwireplumber-module-log-settings, type = module
+    provides = support.log-settings
+  }
+
   ## The lua scripting engine
   {
     name = libwireplumber-module-lua-scripting, type = module