Show Home Link In wp_nav_menu but only on primary menu

Question

This function adds a home link into my nav menu, but it is added to 3 other menus I am using as well. I don't quite understand where to add code to only display in my primary nav.

function my_page_menu_args( $args ) {
    $args['show_home'] = true;
    return $args;
}
add_filter( 'wp_page_menu_args', 'my_page_menu_args' );

Answer 1

function my_page_menu_args( $args ) {
    if($args['theme_location'] === 'primary')
        $args['show_home'] = true;
    return $args;
}
add_filter( 'wp_page_menu_args', 'my_page_menu_args' );

The $args array also contains the theme location, so you can filter on that.