alchemy_calc_div
tdv = alchemy_calc_div(req->rate, pr, scale, maxdiv, NULL);
tdv = alchemy_calc_div(req->rate, pr, scale, maxdiv,
ret = alchemy_calc_div(rate, parent_rate, 2, 512, &div);
ret = alchemy_calc_div(rate, parent_rate, v ? 1 : 2,