snd_mtpav_mputreg
snd_mtpav_mputreg(chip, DREG, byte);
snd_mtpav_mputreg(chip, CREG, clrwrite); // clear write bit
snd_mtpav_mputreg(chip, CREG, setwrite); // set write bit
snd_mtpav_mputreg(mtp_card, CREG, (SIGC_INTEN | SIGC_WRITE)); // enable pport interrupts
snd_mtpav_mputreg(mtp_card, CREG, 0); // disable pport interrupts
snd_mtpav_mputreg(mcrd, CREG, setread);
snd_mtpav_mputreg(mcrd, CREG, clrread);