INSERT INTO `mdl_log_display` VALUES ('groupware', 'add', 'resource', 'name');
No, the add action for your groupware module exists (it's one of the required actions)!!
You can use another action like:
INSERT INTO `mdl_log_display` VALUES ('groupware', 'add resource', 'resource', 'name');
(if the action is to add a resource to your module)
And the final part "....'resource', 'name');"
tells Moodle to search the resource table to get the name field when the id was equal to the info field saved in log table.
Understand now ?
Ciao