AHCI_CMDH_SIZE
(AHCI_RFIS_SIZE + AHCI_CMDH_SIZE) * sc->sc_atac.atac_nchannels;
((char *)cmdhp + AHCI_CMDH_SIZE * port);
AHCI_CMDH_SIZE * port;
AHCI_CMDH_SIZE * sc->sc_atac.atac_nchannels +
AHCI_CMDH_SIZE * sc->sc_atac.atac_nchannels +
(AHCI_RFIS_SIZE + AHCI_CMDH_SIZE) * sc->sc_atac.atac_nchannels);