OHCI1394_IsoRecvIntMaskSet
reg_write(ohci, OHCI1394_IsoRecvIntMaskSet, 1 << index);
reg_write(ohci, OHCI1394_IsoRecvIntMaskSet, ~0);
ohci->ir_context_support = reg_read(ohci, OHCI1394_IsoRecvIntMaskSet);