static void lsi_reg_writeb(LSIState *s, int offset, uint8_t val)
{
#define CASE_SET_REG24(name, addr) \
    case addr    : s->name &= 0xffffff00; s->name |= val;       break; \
    case addr + 1: s->name &= 0xffff00ff; s->name |= val << 8;  break; \
    case addr + 2: s->name &= 0xff00ffff; s->name |= val << 16; break;

#define CASE_SET_REG32(name, addr) \
    case addr    : s->name &= 0xffffff00; s->name |= val;       break; \
    case addr + 1: s->name &= 0xffff00ff; s->name |= val << 8;  break; \
    case addr + 2: s->name &= 0xff00ffff; s->name |= val << 16; break; \
    case addr + 3: s->name &= 0x00ffffff; s->name |= val << 24; break;

    trace_lsi_reg_write(offset < ARRAY_SIZE(names) ? names[offset] : "???",
                        offset, val);

    switch (offset) {
    case 0x00: /* SCNTL0 */
        s->scntl0 = val;
        if (val & LSI_SCNTL0_START) {
            qemu_log_mask(LOG_UNIMP,
                          "lsi_scsi: Start sequence not implemented\n");
        }
        break;
    case 0x01: /* SCNTL1 */
        s->scntl1 = val & ~LSI_SCNTL1_SST;
        if (val & LSI_SCNTL1_IARB) {
            qemu_log_mask(LOG_UNIMP,
                      "lsi_scsi: Immediate Arbritration not implemented\n");
        }
        if (val & LSI_SCNTL1_RST) {
            if (!(s->sstat0 & LSI_SSTAT0_RST)) {
                qbus_reset_all(BUS(&s->bus));
                s->sstat0 |= LSI_SSTAT0_RST;
                lsi_script_scsi_interrupt(s, LSI_SIST0_RST, 0);
            }
        } else {
            s->sstat0 &= ~LSI_SSTAT0_RST;
        }
        break;
    case 0x02: /* SCNTL2 */
        val &= ~(LSI_SCNTL2_WSR | LSI_SCNTL2_WSS);
        s->scntl2 = val;
        break;
    case 0x03: /* SCNTL3 */
        s->scntl3 = val;
        break;
    case 0x04: /* SCID */
        s->scid = val;
        break;
    case 0x05: /* SXFER */
        s->sxfer = val;
        break;
    case 0x06: /* SDID */
        if ((s->ssid & 0x80) && (val & 0xf) != (s->ssid & 0xf)) {
            qemu_log_mask(LOG_GUEST_ERROR,
                          "lsi_scsi: Destination ID does not match SSID\n");
        }
        s->sdid = val & 0xf;
        break;
    case 0x07: /* GPREG0 */
        break;
    case 0x08: /* SFBR */
        /* The CPU is not allowed to write to this register.  However the
           SCRIPTS register move instructions are.  */
        s->sfbr = val;
        break;
    case 0x0a: case 0x0b:
        /* Openserver writes to these readonly registers on startup */
        return;
    case 0x0c: case 0x0d: case 0x0e: case 0x0f:
        /* Linux writes to these readonly registers on startup.  */
        return;
    CASE_SET_REG32(dsa, 0x10)
    case 0x14: /* ISTAT0 */
        s->istat0 = (s->istat0 & 0x0f) | (val & 0xf0);
        if (val & LSI_ISTAT0_ABRT) {
            lsi_script_dma_interrupt(s, LSI_DSTAT_ABRT);
        }
        if (val & LSI_ISTAT0_INTF) {
            s->istat0 &= ~LSI_ISTAT0_INTF;
            lsi_update_irq(s);
        }
        if (s->waiting == LSI_WAIT_RESELECT && val & LSI_ISTAT0_SIGP) {
            trace_lsi_awoken();
            s->waiting = LSI_NOWAIT;
            s->dsp = s->dnad;
            lsi_execute_script(s);
        }
        if (val & LSI_ISTAT0_SRST) {
            qdev_reset_all(DEVICE(s));
        }
        break;
    case 0x16: /* MBOX0 */
        s->mbox0 = val;
        break;
    case 0x17: /* MBOX1 */
        s->mbox1 = val;
        break;
    case 0x18: /* CTEST0 */
        /* nothing to do */
        break;
    case 0x1a: /* CTEST2 */
        s->ctest2 = val & LSI_CTEST2_PCICIE;
        break;
    case 0x1b: /* CTEST3 */
        s->ctest3 = val & 0x0f;
        break;
    CASE_SET_REG32(temp, 0x1c)
    case 0x21: /* CTEST4 */
        if (val & 7) {
            qemu_log_mask(LOG_UNIMP,
                          "lsi_scsi: Unimplemented CTEST4-FBL 0x%x\n", val);
        }
        s->ctest4 = val;
        break;
    case 0x22: /* CTEST5 */
        if (val & (LSI_CTEST5_ADCK | LSI_CTEST5_BBCK)) {
            qemu_log_mask(LOG_UNIMP,
                          "lsi_scsi: CTEST5 DMA increment not implemented\n");
        }
        s->ctest5 = val;
        break;
    CASE_SET_REG24(dbc, 0x24)
    CASE_SET_REG32(dnad, 0x28)
    case 0x2c: /* DSP[0:7] */
        s->dsp &= 0xffffff00;
        s->dsp |= val;
        break;
    case 0x2d: /* DSP[8:15] */
        s->dsp &= 0xffff00ff;
        s->dsp |= val << 8;
        break;
    case 0x2e: /* DSP[16:23] */
        s->dsp &= 0xff00ffff;
        s->dsp |= val << 16;
        break;
    case 0x2f: /* DSP[24:31] */
        s->dsp &= 0x00ffffff;
        s->dsp |= val << 24;
        /*
         * FIXME: if s->waiting != LSI_NOWAIT, this will only execute one
         * instruction.  Is this correct?
         */
        if ((s->dmode & LSI_DMODE_MAN) == 0
            && (s->istat1 & LSI_ISTAT1_SRUN) == 0)
            lsi_execute_script(s);
        break;
    CASE_SET_REG32(dsps, 0x30)
    CASE_SET_REG32(scratch[0], 0x34)
    case 0x38: /* DMODE */
        s->dmode = val;
        break;
    case 0x39: /* DIEN */
        s->dien = val;
        lsi_update_irq(s);
        break;
    case 0x3a: /* SBR */
        s->sbr = val;
        break;
    case 0x3b: /* DCNTL */
        s->dcntl = val & ~(LSI_DCNTL_PFF | LSI_DCNTL_STD);
        /*
         * FIXME: if s->waiting != LSI_NOWAIT, this will only execute one
         * instruction.  Is this correct?
         */
        if ((val & LSI_DCNTL_STD) && (s->istat1 & LSI_ISTAT1_SRUN) == 0)
            lsi_execute_script(s);
        break;
    case 0x40: /* SIEN0 */
        s->sien0 = val;
        lsi_update_irq(s);
        break;
    case 0x41: /* SIEN1 */
        s->sien1 = val;
        lsi_update_irq(s);
        break;
    case 0x47: /* GPCNTL0 */
        break;
    case 0x48: /* STIME0 */
        s->stime0 = val;
        break;
    case 0x49: /* STIME1 */
        if (val & 0xf) {
            qemu_log_mask(LOG_UNIMP,
                          "lsi_scsi: General purpose timer not implemented\n");
            /* ??? Raising the interrupt immediately seems to be sufficient
               to keep the FreeBSD driver happy.  */
            lsi_script_scsi_interrupt(s, 0, LSI_SIST1_GEN);
        }
        break;
    case 0x4a: /* RESPID0 */
        s->respid0 = val;
        break;
    case 0x4b: /* RESPID1 */
        s->respid1 = val;
        break;
    case 0x4d: /* STEST1 */
        s->stest1 = val;
        break;
    case 0x4e: /* STEST2 */
        if (val & 1) {
            qemu_log_mask(LOG_UNIMP,
                          "lsi_scsi: Low level mode not implemented\n");
        }
        s->stest2 = val;
        break;
    case 0x4f: /* STEST3 */
        if (val & 0x41) {
            qemu_log_mask(LOG_UNIMP,
                          "lsi_scsi: SCSI FIFO test mode not implemented\n");
        }
        s->stest3 = val;
        break;
    case 0x56: /* CCNTL0 */
        s->ccntl0 = val;
        break;
    case 0x57: /* CCNTL1 */
        s->ccntl1 = val;
        break;
    CASE_SET_REG32(mmrs, 0xa0)
    CASE_SET_REG32(mmws, 0xa4)
    CASE_SET_REG32(sfs, 0xa8)
    CASE_SET_REG32(drs, 0xac)
    CASE_SET_REG32(sbms, 0xb0)
    CASE_SET_REG32(dbms, 0xb4)
    CASE_SET_REG32(dnad64, 0xb8)
    CASE_SET_REG32(pmjad1, 0xc0)
    CASE_SET_REG32(pmjad2, 0xc4)
    CASE_SET_REG32(rbc, 0xc8)
    CASE_SET_REG32(ua, 0xcc)
    CASE_SET_REG32(ia, 0xd4)
    CASE_SET_REG32(sbc, 0xd8)
    CASE_SET_REG32(csbc, 0xdc)
    default:
        if (offset >= 0x5c && offset < 0xa0) {
            int n;
            int shift;
            n = (offset - 0x58) >> 2;
            shift = (offset & 3) * 8;
            s->scratch[n] = deposit32(s->scratch[n], shift, 8, val);
        } else {
            qemu_log_mask(LOG_GUEST_ERROR,
                          "lsi_scsi: invalid write to reg %s %x (0x%02x)\n",
                          offset < ARRAY_SIZE(names) ? names[offset] : "???",
                          offset, val);
        }
    }
#undef CASE_SET_REG24
#undef CASE_SET_REG32
}