import re


def is_valid_vpsa_display_name(vpsa_display_name):
    """
    Validates a Zadara VPSA display name.  Only alphanumeric characters and
    underscore are allowed.

    :type vpsa_display_name: str
    :param vpsa_display_name: The VPSA display name to be validated.

    :rtype: bool
    :return: True or False depending on whether vpsa_display_name passes
        validation.
    """
    if vpsa_display_name is None:
        return False

    match = re.match(r'^[A-Za-z-0-9_]+$', vpsa_display_name)

    if not match:
        return False

    return True