SCSISIGO
if ((ahd_inb(ahd, SCSISIGO) & ATNO) != 0
ahd_outb(ahd, SCSISIGO, ATNO);
ahd_outb(ahd, SCSISIGO, 0); /* De-assert BSY */
if ((ahd_inb(ahd, SCSISIGO) & ATNO) != 0) {
ahd_outb(ahd, SCSISIGO, P_MESGOUT | BSYO);
ahd_outb(ahd, SCSISIGO, P_MESGIN | BSYO);
&& (ahd_inb(ahd, SCSISIGO) & ATNO) != 0) {
ahc_outb(ahc, SCSISIGO, scsisigo);
ahc_outb(ahc, SCSISIGO, 0); /* De-assert BSY */
ahc_outb(ahc, SCSISIGO, P_MESGOUT | BSYO);
ahc_outb(ahc, SCSISIGO, P_MESGIN | BSYO);
ahc_outb(ahc, SCSISIGO, curphase);