ARITH_SHIFT
int device_constant = 1 << ARITH_SHIFT;
int test_frame_len = TEST_FRAME_LEN << ARITH_SHIFT;
int s_unit = 1 << ARITH_SHIFT;
err = (fail_avg << ARITH_SHIFT) / 100;
estimated_retx = ((1 << (2 * ARITH_SHIFT)) / (s_unit - err));
result = ((u64)tx_time * estimated_retx) >> (2 * ARITH_SHIFT);