def send_nvme_cmd(client, name, cmd_type, data_direction, cmdbuf,
                  data=None, metadata=None,
                  data_len=None, metadata_len=None,
                  timeout_ms=None):
    """Send one NVMe command

    Args:
        name: Name of the operating NVMe controller
        cmd_type: Type of nvme cmd. Valid values are: admin, io
        data_direction: Direction of data transfer. Valid values are: c2h, h2c
        cmdbuf: NVMe command encoded by base64 urlsafe
        data: Data transferring to controller from host, encoded by base64 urlsafe
        metadata: metadata transferring to controller from host, encoded by base64 urlsafe
        data_length: Data length required to transfer from controller to host
        metadata_length: Metadata length required to transfer from controller to host
        timeout-ms: Command execution timeout value, in milliseconds, if 0, don't track timeout

    Returns:
        NVMe completion queue entry, requested data and metadata, all are encoded by base64 urlsafe.
    """
    params = {'name': name,
              'cmd_type': cmd_type,
              'data_direction': data_direction,
              'cmdbuf': cmdbuf}

    if data:
        params['data'] = data
    if metadata:
        params['metadata'] = metadata
    if data_len:
        params['data_len'] = data_len
    if metadata_len:
        params['metadata_len'] = metadata_len
    if timeout_ms:
        params['timeout_ms'] = timeout_ms

    return client.call('send_nvme_cmd', params)


def get_nvme_controllers(client, name=None):
    """Get information about NVMe controllers.

    Args:
        name: NVMe controller name to query (optional; if omitted, query all NVMe controllers)

    Returns:
        List of NVMe controller information objects.
    """
    params = {}
    if name:
        params['name'] = name
    return client.call('get_nvme_controllers', params)