SD_DEF_XFER_BLOCKS
if (sdkp->opt_xfer_blocks > SD_DEF_XFER_BLOCKS) {
sdkp->opt_xfer_blocks, SD_DEF_XFER_BLOCKS);
dev_max = sdp->use_16_for_rw ? SD_MAX_XFER_BLOCKS : SD_DEF_XFER_BLOCKS;