How to use ajax on a field widget submit button in Drupal 7 without validating the rest of the form

I'm making a new widget for taxonomy term references where a submit button makes an ajax call back to drupal to alter the form. Here's what I have:

$element['my_module_wrapper']['add'] = array(  
  '#type' => 'submit',  
  '#value' => t('Add'),  
  '#ajax' => array(  
    'callback' => 'my_module_ajax',  
 开发者_开发问答   'wrapper' => $field_name . '_my_module_container',  
  ),
);

I have the ajax call working properly, but it validates the whole form, and throws errors when unrelated fields that are required aren't filled out. How can I stop this?

Also possibly related, it doesn't seem to call my hook_field_widget_form() function when ajax is called... is this stemming from the same problem?

Have you tried making your field #type = 'button' instead of 'submit'? As far as I know, a submit button will always run through the for validate array whether it's an ajax form item or not.

Look at the example from Poll module given here: http://api.drupal.org/api/drupal/developer--topics--forms_api_reference.html/7#ajax

The full function shows how it's done with '#limit_validation_errors'.