I2C_FIFO_CONTROL_REG
I2C_WRITE(sc, I2C_FIFO_CONTROL_REG,
I2C_SET_CLEAR(sc, I2C_FIFO_CONTROL_REG, flush_mask, 0);
const uint32_t v = I2C_READ(sc, I2C_FIFO_CONTROL_REG);