code: func CheckFsp(fsp int) (int, error) {
  	if fsp == UnspecifiedFsp {
  		return DefaultFsp, nil
  	}
  	if fsp < MinFsp || fsp > MaxFsp {
  		return DefaultFsp, errors.Errorf("Invalid fsp %d", fsp)
  	}
  	return fsp, nil
  }
docs: // CheckFsp checks whether fsp is in valid range.