AD7944_SPI_BYTES
xfers[2].len = AD7944_SPI_BYTES(chan->scan_type);
xfers[1].len = AD7944_SPI_BYTES(chan->scan_type);
xfers[1].len = AD7944_SPI_BYTES(chan->scan_type) * n_chain_dev;
xfers[1].len = AD7944_SPI_BYTES(chan->scan_type);
AD7944_SPI_BYTES(chan[0].scan_type), sizeof(u64)) + sizeof(u64);