Drupal: change maxlength and size of description field in default upload widget

msw_custom.module

<?php
/**
 * @file
 * The description used as label of the link to the uploaded file has default lentgh=128 and size=60.
 * With this function inside your custom module you can change these (and other) default options.
 */

/**
 * Implements hook_preprocess_file_widget().
 */
function msw_custom_preprocess_file_widget(&$vars) {
  if (isset($vars['element']['#file']) && is_object($vars['element']['#file'])) {
    $vars['element']['description']['#maxlength'] = 600;
    $vars['element']['description']['#size'] = 120;
  }
}