HAL_REO1_RING_MSI1_BASE_LSB
(HAL_REO1_RING_MSI1_BASE_LSB(ab) - HAL_REO1_RING_BASE_LSB(ab))
return HAL_REO1_RING_MSI1_BASE_LSB(hal) - HAL_REO1_RING_BASE_LSB(hal);