OHCI_ITOFF
off = OHCI_ITOFF(dmach);
#define OHCI_ITCTL(CH) (OHCI_ITOFF(CH))
#define OHCI_ITCTLCLR(CH) (OHCI_ITOFF(CH) + 4)
#define OHCI_ITCMD(CH) (OHCI_ITOFF(CH) + 0xc)