DFH
v = readq(binfo->ioaddr + DFH);
v = readq(binfo->ioaddr + ofst + DFH);
v = readq(binfo->ioaddr + start - binfo->start + DFH);
#define FME_HDR_DFH DFH
#define PORT_HDR_DFH DFH
u64 v = readq(base + DFH);
u64 v = readq(base + DFH);
return (u8)FIELD_GET(DFH_REVISION, readq(base + DFH));