unsigned int driver_poll(struct file *instance,
                         struct poll_table_struct *event_list)
{
  unsigned int mask = 0;

  poll_wait(instance, &wq_read, event_list);
  poll_wait(instance, &wq_write, event_list);
  if (READ_POSSIBLE)
    mask |= POLLIN | POLLRDNORM;
  if (WRITE_POSSIBLE)
    mask |= POLLOUT | POLLWRNORM;
  return mask;
}