XADC_REG_THRESHOLD
xadc_read_adc_reg(xadc, XADC_REG_THRESHOLD(i),
ret = _xadc_write_adc_reg(xadc, XADC_REG_THRESHOLD(offset + 4),
ret = _xadc_write_adc_reg(xadc, XADC_REG_THRESHOLD(offset), val);