reg = inb(hwif->dma_base + 0x02 + 8*controller);
reg |= 1<<((drive->dn&1)+5);
outb(reg, hwif->dma_base + 0x02 + 8*controller);
reg = inb(hwif->dma_base + 0x02 + 8*controller);
reg |= 1<<((drive->dn&1)+5);
outb(reg, hwif->dma_base + 0x02 + 8*controller);