+@brief
+ Logging level enumerators and library logging control.
+
+The logging API offers logging level enumerators (#bt_logging_level)
+as well as functions to control libbabeltrace2's internal logging.
+
+@note
+ This API does \em not offer macros and functions to write logging
+ statements: as of \bt_name_version_min_maj, the actual mechanism to
+ log is implementation-defined for each user \bt_plugin.
+
+libbabeltrace2 contains many hundreds of logging statements to help you
+follow and debug your plugin or program.
+
+The library's initial logging level is controlled by the
+\c LIBBABELTRACE2_INIT_LOG_LEVEL environment variable. If this
+environment variable is not set at library load time, the library's
+initial logging level is #BT_LOGGING_LEVEL_NONE. See
+\ref api-fund-logging to learn more.
+
+Set libbabeltrace2's current logging level with
+bt_logging_set_global_level().
+
+\anchor api-logging-extra-lib bt_logging_set_global_level() only
+controls <strong>libbabeltrace2</strong>'s logging level; it does \em
+not control the logging level of:
+
+- Individual \bt_p_comp: bt_graph_add_source_component(),
+ bt_graph_add_source_component_with_initialize_method_data(),
+ bt_graph_add_filter_component(),
+ bt_graph_add_filter_component_with_initialize_method_data(),
+ bt_graph_add_sink_component(), and
+ bt_graph_add_sink_component_with_initialize_method_data() control
+ this.