ohci_td_t
usb_syncmem(&p->dma, p->offs + offsetof(ohci_td_t, td_flags),
std->offs + offsetof(ohci_td_t, td_flags),
#define OHCI_TD_SIZE (roundup(sizeof(ohci_td_t), OHCI_TD_ALLOC_ALIGN))
ohci_td_t *td;