AT_DRVHD
ata_ctlp->ac_drvhd = (uchar_t *)ioaddr1 + AT_DRVHD;
ddi_put8(io_hdl1, (uchar_t *)ioaddr1 + AT_DRVHD, drvhd);
ddi_put8(io_hdl1, (uchar_t *)ioaddr1 + AT_DRVHD,
ddi_put8(io_hdl1, (uchar_t *)ioaddr1 + AT_DRVHD,