def write_validate(ctx, param, value):
    if value != ("default", "default"):
        try:
            mode, dest_file = (value[0], value[1])
        except IndexError:
            raise click.BadParameter('Expecting two arguments, one for how to '
                                     'output (s, single, m, multiple), and '
                                     'the second is a filepath where to put'
                                     ' the output.')
        if mode.lower() not in ['s', 'single', 'm', 'multiple']:
            raise click.BadParameter('The first argument of the -w/--write '
                                     'option must specifies whether to write'
                                     ' to one file per device, or all device'
                                     ' output to a single file. Valid options'
                                     ' are "s", "single", "m", and "multiple"')
        ctx.obj['out'] = (mode.lower(), dest_file)
    else:
        ctx.obj['out'] = None