ata_down_xfermask_limit
if (ata_down_xfermask_limit(dev, sel) == 0) {
if (ata_down_xfermask_limit(dev, ATA_DNXFER_FORCE_PIO) == 0) {
ata_down_xfermask_limit(dev, ATA_DNXFER_PIO);
ata_down_xfermask_limit(dev, ATA_DNXFER_FORCE_PIO0 | ATA_DNXFER_QUIET);
extern int ata_down_xfermask_limit(struct ata_device *dev, unsigned int sel);