src/devices/dev_asc.c

/*
 *  Copyright (C) 2003-2006  Anders Gavare.  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright  
 *     notice, this list of conditions and the following disclaimer in the 
 *     documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 *  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE   
 *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 *  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 *  OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 *  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 *  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 *  SUCH DAMAGE.
 *
 *
 *  $Id: dev_asc.c,v 1.81 2006/07/21 16:55:41 debug Exp $
 *
 *  'asc' SCSI controller for some DECstation/DECsystem models and PICA-61.
 *
 *  Supposed to support SCSI-1 and SCSI-2. I've not yet found any docs
 *  on NCR53C9X, so I'll try to implement this device from LSI53CF92A docs
 *  instead.
 *
 *
 *  Memory layout on DECstation:
 *
 *      NCR53C94 registers      at base + 0
 *      DMA address register    at base + 0x40000
 *      128K SRAM buffer        at base + 0x80000
 *      ROM                     at base + 0xc0000
 *
 *  Memory layout on PICA-61:
 *
 *      I haven't had time to look this up yet, but length = 0x1000.
 *
 *
 *  TODO:  This module needs a clean-up, and some testing to see that
 *         it works will all OSes that might use it (NetBSD, OpenBSD,
 *         Ultrix, Linux, Mach, OSF/1, Sprite, ...)
 *
 *         Running Linux/DECstation 2.4.26 with no scsi disks attached causes
 *         a warning message to be printed by Linux. (Whether this is a bug,
 *         is is the way it works on real hardware, I don't know.)
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "cpu.h"
#include "devices.h"
#include "diskimage.h"
#include "machine.h"
#include "memory.h"
#include "misc.h"

#include "ncr53c9xreg.h"


/*  #define ASC_DEBUG  */
/*  #define debug fatal  */
/*  #define ASC_FULL_REGISTER_ACCESS_DEBUG  */
/*  static int quiet_mode = 0;  */

#define ASC_TICK_SHIFT          15

extern int quiet_mode;


#define ASC_FIFO_LEN            16
#define STATE_DISCONNECTED      0
#define STATE_INITIATOR         1
#define STATE_TARGET            2

#define PHASE_DATA_OUT          0
#define PHASE_DATA_IN           1
#define PHASE_COMMAND           2
#define PHASE_STATUS            3
#define PHASE_MSG_OUT           6
#define PHASE_MSG_IN            7


/*  The controller's SCSI id:  */
#define ASC_SCSI_ID             7

#define ASC_DMA_SIZE            (128*1024)

struct asc_data {
        int             mode;

        void            *turbochannel;
        int             irq_nr;
        int             irq_caused_last_time;

        /*  Current state and transfer:  */
        int             cur_state;
        int             cur_phase;
        struct scsi_transfer *xferp;

        /*  FIFO:  */
        unsigned char   fifo[ASC_FIFO_LEN];
        int             fifo_in;
        int             fifo_out;
        int             n_bytes_in_fifo;                /*  cached  */

        /*  ATN signal:  */
        int             atn;

        /*  Incoming dma data:  */
        unsigned char   *incoming_data;
        int             incoming_len;
        int             incoming_data_addr;

        /*  Built-in DMA memory (for DECstation 5000/200):  */
        uint32_t        dma_address_reg;
        unsigned char   *dma_address_reg_memory;
        unsigned char   *dma;

        void            *dma_controller_data;
        size_t          (*dma_controller)(void *dma_controller_data,
                            unsigned char *data, size_t len, int writeflag);

        /*  Read registers and write registers:  */
        uint32_t        reg_ro[0x10];
        uint32_t        reg_wo[0x10];
};

/*  (READ/WRITE name, if split)  */
char *asc_reg_names[0x10] = {
        "NCR_TCL", "NCR_TCM", "NCR_FIFO", "NCR_CMD",
        "NCR_STAT/NCR_SELID", "NCR_INTR/NCR_TIMEOUT",
        "NCR_STEP/NCR_SYNCTP", "NCR_FFLAG/NCR_SYNCOFF",
        "NCR_CFG1", "NCR_CCF", "NCR_TEST", "NCR_CFG2",
        "NCR_CFG3", "reg_0xd", "NCR_TCH", "reg_0xf"
};


/*  This is referenced below.  */
static int dev_asc_select(struct cpu *cpu, struct asc_data *d, int from_id,
        int to_id, int dmaflag, int n_messagebytes);


DEVICE_TICK(asc)
{
        struct asc_data *d = extra;

        if (d->reg_ro[NCR_STAT] & NCRSTAT_INT)
                cpu_interrupt(cpu, d->irq_nr);
}


/*
 *  dev_asc_fifo_flush():
 *
 *  Flush the fifo.
 */
static void dev_asc_fifo_flush(struct asc_data *d)
{
        d->fifo[0] = 0x00;
        d->fifo_in = 0;
        d->fifo_out = 0;
        d->n_bytes_in_fifo = 0;
}


/*
 *  dev_asc_reset():
 *
 *  Reset the state of the asc.
 */
static void dev_asc_reset(struct asc_data *d)
{
        d->cur_state = STATE_DISCONNECTED;
        d->atn = 0;

        if (d->xferp != NULL)
                scsi_transfer_free(d->xferp);
        d->xferp = NULL;

        dev_asc_fifo_flush(d);

        /*  According to table 4.1 in the LSI53CF92A manual:  */
        memset(d->reg_wo, 0, sizeof(d->reg_wo));
        d->reg_wo[NCR_TCH] = 0x94;
        d->reg_wo[NCR_CCF] = 2;
        memcpy(d->reg_ro, d->reg_wo, sizeof(d->reg_ro));
        d->reg_wo[NCR_SYNCTP] = 5;
}


/*
 *  dev_asc_fifo_read():
 *
 *  Read a byte from the asc FIFO.
 */
static int dev_asc_fifo_read(struct asc_data *d)
{
        int res = d->fifo[d->fifo_out];

        if (d->fifo_in == d->fifo_out)
                fatal("dev_asc: WARNING! FIFO overrun!\n");

        d->fifo_out = (d->fifo_out + 1) % ASC_FIFO_LEN;
        d->n_bytes_in_fifo --;

        return res;
}


/*
 *  dev_asc_fifo_write():
 *
 *  Write a byte to the asc FIFO.
 */
static void dev_asc_fifo_write(struct asc_data *d, unsigned char data)
{
        d->fifo[d->fifo_in] = data;
        d->fifo_in = (d->fifo_in + 1) % ASC_FIFO_LEN;
        d->n_bytes_in_fifo ++;

        if (d->fifo_in == d->fifo_out)
                fatal("dev_asc: WARNING! FIFO overrun on write!\n");
}


/*
 *  dev_asc_newxfer():
 *
 *  Allocate memory for a new transfer.
 */
static void dev_asc_newxfer(struct asc_data *d)
{
        if (d->xferp != NULL) {
                printf("WARNING! dev_asc_newxfer(): freeing previous"
                    " transfer\n");
                scsi_transfer_free(d->xferp);
                d->xferp = NULL;
        }

        d->xferp = scsi_transfer_alloc();
#if 0
        d->xferp->get_data_out = dev_asc_get_data_out;
        d->xferp->gdo_extra = (void *) d;
#endif
}


/*
 *  dev_asc_transfer():
 *
 *  Transfer data from a SCSI device to the controller (or vice versa),
 *  depending on the current phase.
 *
 *  Returns 1 if ok, 0 on error.
 */
static int dev_asc_transfer(struct cpu *cpu, struct asc_data *d, int dmaflag)
{
        int res = 1, all_done = 1;
        int len, i, ch;

        if (!quiet_mode)
                debug(" { TRANSFER to/from id %i: ", d->reg_wo[NCR_SELID] & 7);

        if (d->cur_phase == PHASE_DATA_IN) {
                /*  Data coming into the controller from external device:  */
                if (!dmaflag) {
                        if (d->xferp->data_in == NULL) {
                                fatal("no incoming data?\n");
                                res = 0;
                        } else {
/*  TODO  */
fatal("TODO..............\n");
                                len = d->reg_wo[NCR_TCL] +
                                    d->reg_wo[NCR_TCM] * 256;

                                len--;
                                ch = d->incoming_data[d->incoming_data_addr];
                                debug(" %02x", ch);

                                d->incoming_data_addr ++;
                                dev_asc_fifo_write(d, ch);

                                if (len == 0) {
                                        free(d->incoming_data);
                                        d->incoming_data = NULL;
                                }

                                d->reg_ro[NCR_TCL] = len & 255;
                                d->reg_ro[NCR_TCM] = (len >> 8) & 255;
                        }
                } else {
                        /*  Copy from the incoming data into dma memory:  */
                        if (d->xferp->data_in == NULL) {
                                fatal("no incoming DMA data?\n");
                                res = 0;
                        } else {
                                size_t len = d->xferp->data_in_len;
                                size_t len2 = d->reg_wo[NCR_TCL] +
                                    d->reg_wo[NCR_TCM] * 256;
                                if (len2 == 0)
                                        len2 = 65536;

                                if (len < len2) {
                                        fatal("{ asc: data in, len=%i len2=%i "
                                            "}\n", len, len2);
                                }

                                /*  TODO: check len2 in a similar way?  */
                                if (len + (d->dma_address_reg &
                                    (ASC_DMA_SIZE-1)) > ASC_DMA_SIZE)
                                        len = ASC_DMA_SIZE -
                                            (d->dma_address_reg &
                                            (ASC_DMA_SIZE-1));

                                if (len2 > len) {
                                        memset(d->dma + (d->dma_address_reg &
                                            (ASC_DMA_SIZE-1)), 0, len2);
                                        len2 = len;
                                }

#ifdef ASC_DEBUG
                                if (!quiet_mode) {
                                        int i;
                                        for (i=0; i<len; i++)
                                                debug(" %02x", d->xferp->
                                                    data_in[i]);
                                }
#endif

                                /*
                                 *  Are we using an external DMA controller?
                                 *  Then use it. Otherwise place the data in
                                 *  the DECstation 5000/200 built-in DMA
                                 *  region.
                                 */
                                if (d->dma_controller != NULL)
                                        d->dma_controller(
                                            d->dma_controller_data,
                                            d->xferp->data_in,
                                            len2, 1);
                                else
                                        memcpy(d->dma + (d->dma_address_reg &
                                            (ASC_DMA_SIZE-1)),
                                            d->xferp->data_in, len2);

                                if (d->xferp->data_in_len > len2) {
                                        unsigned char *n;

if (d->dma_controller != NULL)
        printf("WARNING!!!!!!!!! BUG!!!! Unexpected stuff..."
            "len2=%i d->xferp->data_in_len=%i\n", (int)len2,
            (int)d->xferp->data_in_len);

                                        all_done = 0;
                                        /*  fatal("{ asc: multi-transfer"
                                            " data_in, len=%i len2=%i }\n",
                                            (int)len, (int)len2);  */

                                        d->xferp->data_in_len -= len2;
                                        n = malloc(d->xferp->data_in_len);
                                        if (n == NULL) {
                                                fprintf(stderr, "out of memory"
                                                    " in dev_asc\n");
                                                exit(1);
                                        }
                                        memcpy(n, d->xferp->data_in + len2,
                                            d->xferp->data_in_len);
                                        free(d->xferp->data_in);
                                        d->xferp->data_in = n;

                                        len = len2;
                                }

                                len = 0;

                                d->reg_ro[NCR_TCL] = len & 255;
                                d->reg_ro[NCR_TCM] = (len >> 8) & 255;

                                /*  Successful DMA transfer:  */
                                d->reg_ro[NCR_STAT] |= NCRSTAT_TC;
                        }
                }
        } else if (d->cur_phase == PHASE_DATA_OUT) {
                /*  Data going from the controller to an external device:  */
                if (!dmaflag) {
fatal("TODO.......asdgasin\n");
                } else {
                        /*  Copy data from DMA to data_out:  */
                        int len = d->xferp->data_out_len;
                        int len2 = d->reg_wo[NCR_TCL] +
                            d->reg_wo[NCR_TCM] * 256;
                        if (len2 == 0)
                                len2 = 65536;

                        if (len == 0) {
                                fprintf(stderr, "d->xferp->data_out_len == "
                                    "0 ?\n");
                                exit(1);
                        }

                        /*  TODO: Make sure that len2 doesn't go outside
                            of the dma memory?  */

                        /*  fatal("    data out offset=%5i len=%5i\n",
                            d->xferp->data_out_offset, len2);  */

                        if (d->xferp->data_out_offset + len2 >
                            d->xferp->data_out_len) {
                                len2 = d->xferp->data_out_len -
                                    d->xferp->data_out_offset;
                        }

                        /*
                         *  Are we using an external DMA controller? Then use
                         *  it. Otherwise place the data in the DECstation
                         *  5000/200 built-in DMA region.
                         */
                        if (d->xferp->data_out == NULL) {
                                scsi_transfer_allocbuf(&d->xferp->data_out_len,
                                    &d->xferp->data_out, len, 0);

                                if (d->dma_controller != NULL)
                                        d->dma_controller(
                                            d->dma_controller_data,
                                            d->xferp->data_out,
                                            len2, 0);
                                else
                                        memcpy(d->xferp->data_out,
                                            d->dma + (d->dma_address_reg &
                                            (ASC_DMA_SIZE-1)), len2);
                                d->xferp->data_out_offset = len2;
                        } else {
                                /*  Continuing a multi-transfer:  */
                                if (d->dma_controller != NULL)
                                        d->dma_controller(
                                            d->dma_controller_data,
                                            d->xferp->data_out +
                                                d->xferp->data_out_offset,
                                            len2, 0);
                                else
                                        memcpy(d->xferp->data_out +
                                            d->xferp->data_out_offset,
                                            d->dma + (d->dma_address_reg &
                                            (ASC_DMA_SIZE-1)), len2);
                                d->xferp->data_out_offset += len2;
                        }

                        /*  If the disk wants more than we're DMAing,
                            then this is a multitransfer:  */
                        if (d->xferp->data_out_offset !=
                            d->xferp->data_out_len) {
                                if (!quiet_mode)
                                        debug("[ asc: data_out, multitransfer "
                                            "len = %i, len2 = %i ]\n",
                                            (int)len, (int)len2);
                                if (d->xferp->data_out_offset >
                                    d->xferp->data_out_len)
                                        fatal("[ asc data_out dma: too much?"
                                            " ]\n");
                                else
                                        all_done = 0;
                        }

#ifdef ASC_DEBUG
                        if (!quiet_mode) {
                                int i;
                                for (i=0; i<len; i++)
                                        debug(" %02x", d->xferp->data_out[i]);
                        }
#endif
                        len = 0;

                        d->reg_ro[NCR_TCL] = len & 255;
                        d->reg_ro[NCR_TCM] = (len >> 8) & 255;

                        /*  Successful DMA transfer:  */
                        d->reg_ro[NCR_STAT] |= NCRSTAT_TC;
                }
        } else if (d->cur_phase == PHASE_MSG_OUT) {
                if (!quiet_mode)
                        debug("MSG OUT: ");
                /*  Data going from the controller to an external device:  */
                if (!dmaflag) {
                        /*  There should already be one byte in msg_out, so we
                            just extend the message:  */
                        int oldlen = d->xferp->msg_out_len;
                        int newlen;

                        if (oldlen != 1) {
                                fatal(" (PHASE OUT MSG len == %i, "
                                    "should be 1)\n", oldlen);
                        }

                        newlen = oldlen + d->n_bytes_in_fifo;
                        d->xferp->msg_out = realloc(d->xferp->msg_out, newlen);
                        d->xferp->msg_out_len = newlen;
                        if (d->xferp->msg_out == NULL) {
                                fprintf(stderr, "out of memory realloc'ing "
                                    "msg_out\n");
                                exit(1);
                        }

                        i = oldlen;
                        while (d->fifo_in != d->fifo_out) {
                                ch = dev_asc_fifo_read(d);
                                d->xferp->msg_out[i++] = ch;
#ifdef ASC_DEBUG
                                debug("0x%02x ", ch);
#endif
                        }

#ifdef MACH
                        /*  Super-ugly hack for Mach/PMAX:  TODO: make nicer  */
                        if (d->xferp->msg_out_len == 6 &&
                            (d->xferp->msg_out[0] == 0x80 ||
                             d->xferp->msg_out[0] == 0xc0) &&
                            d->xferp->msg_out[1] == 0x01 &&
                            d->xferp->msg_out[2] == 0x03 &&
                            d->xferp->msg_out[3] == 0x01 &&
                            d->xferp->msg_out[4] == 0x32 &&
                            d->xferp->msg_out[5] == 0x0f) {
                                fatal(" !! Mach/PMAX hack !! ");
                                all_done = 0;
                                d->cur_phase = PHASE_MSG_IN;
                        }
#endif
                } else {
                        /*  Copy data from DMA to msg_out:  */
                        fatal("[ DMA MSG OUT: xxx TODO! ]");
                        /*  TODO  */
                        res = 0;
                }
        } else if (d->cur_phase == PHASE_MSG_IN) {
                if (!quiet_mode)
                        debug(" MSG IN");
                fatal("[ MACH HACK! ]");
                /*  Super-ugly hack for Mach/PMAX:  TODO: make nicer  */
                dev_asc_fifo_write(d, 0x07);
                d->cur_phase = PHASE_COMMAND;
                all_done = 0;
        } else if (d->cur_phase == PHASE_COMMAND) {
                if (!quiet_mode)
                        debug(" COMMAND ==> select ");
                res = dev_asc_select(cpu, d, d->reg_ro[NCR_CFG1] & 7,
                    d->reg_wo[NCR_SELID] & 7, dmaflag, 0);
                return res;
        } else {
                fatal("!!! TODO: unknown/unimplemented phase "
                    "in transfer: %i\n", d->cur_phase);
        }

        /*  Redo the command if data was just sent using DATA_OUT:  */
        if (d->cur_phase == PHASE_DATA_OUT) {
                res = diskimage_scsicommand(cpu, d->reg_wo[NCR_SELID] & 7,
                    DISKIMAGE_SCSI, d->xferp);
        }

        if (all_done) {
                if (d->cur_phase == PHASE_MSG_OUT)
                        d->cur_phase = PHASE_COMMAND;
                else
                        d->cur_phase = PHASE_STATUS;
        }

        /*
         *  Cause an interrupt after the transfer:
         *
         *  NOTE:  Earlier I had this in here as well:
         *      d->reg_ro[NCR_INTR] |= NCRINTR_FC;
         *  but Linux/DECstation and OpenBSD/pmax seems to choke on that.
         */
        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
        d->reg_ro[NCR_INTR] |= NCRINTR_BS;
        d->reg_ro[NCR_STAT] = (d->reg_ro[NCR_STAT] & ~7) | d->cur_phase;
        d->reg_ro[NCR_STEP] = (d->reg_ro[NCR_STEP] & ~7) | 4;   /*  4?  */

        if (!quiet_mode)
                debug("}");
        return res;
}


/*
 *  dev_asc_select():
 *
 *  Select a SCSI device, send msg bytes (if any), and send command bytes.
 *  (Call diskimage_scsicommand() to handle the command.)
 *
 *  Return value: 1 if ok, 0 on error.
 */
static int dev_asc_select(struct cpu *cpu, struct asc_data *d, int from_id,
        int to_id, int dmaflag, int n_messagebytes)
{
        int ok, len, i, ch;

        if (!quiet_mode)
                debug(" { SELECT id %i: ", to_id);

        /*
         *  Message bytes, if any:
         */
        if (!quiet_mode)
                debug("msg:");

        if (n_messagebytes > 0) {
                scsi_transfer_allocbuf(&d->xferp->msg_out_len,
                    &d->xferp->msg_out, n_messagebytes, 0);

                i = 0;
                while (n_messagebytes-- > 0) {
                        int ch = dev_asc_fifo_read(d);
                        if (!quiet_mode)
                                debug(" %02x", ch);
                        d->xferp->msg_out[i++] = ch;
                }

                if ((d->xferp->msg_out[0] & 0x7) != 0x00) {
                        debug(" (LUNs not implemented yet: 0x%02x) }",
                            d->xferp->msg_out[0]);
                        return 0;
                }

                if (((d->xferp->msg_out[0] & ~0x7) != 0xc0) &&
                    ((d->xferp->msg_out[0] & ~0x7) != 0x80)) {
                        fatal(" (Unimplemented msg out: 0x%02x) }",
                            d->xferp->msg_out[0]);
                        return 0;
                }

                if (d->xferp->msg_out_len > 1) {
                        fatal(" (Long msg out, not implemented yet;"
                            " len=%i) }", d->xferp->msg_out_len);
                        return 0;
                }
        } else {
                if (!quiet_mode)
                        debug(" none");
        }

        /*  Special case: SELATNS (with STOP sequence):  */
        if (d->cur_phase == PHASE_MSG_OUT) {
                if (!quiet_mode)
                        debug(" MSG OUT DEBUG");
                if (d->xferp->msg_out_len != 1) {
                        fatal(" (SELATNS: msg out len == %i, should be 1)",
                            d->xferp->msg_out_len);
                        return 0;
                }

/* d->cur_phase = PHASE_COMMAND; */

                /*  According to the LSI manual:  */
                d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                d->reg_ro[NCR_INTR] |= NCRINTR_FC;
                d->reg_ro[NCR_INTR] |= NCRINTR_BS;
                d->reg_ro[NCR_STAT] = (d->reg_ro[NCR_STAT] & ~7) | d->cur_phase;
                d->reg_ro[NCR_STEP] = (d->reg_ro[NCR_STEP] & ~7) | 1;

                if (!quiet_mode)
                        debug("}");
                return 1;
        }

        /*
         *  Command bytes:
         */
        if (!quiet_mode)
                debug(", cmd: ");

        if (!dmaflag) {
                if (!quiet_mode)
                        debug("[non-DMA] ");

                scsi_transfer_allocbuf(&d->xferp->cmd_len,
                    &d->xferp->cmd, d->n_bytes_in_fifo, 0);

                i = 0;
                while (d->fifo_in != d->fifo_out) {
                        ch = dev_asc_fifo_read(d);
                        d->xferp->cmd[i++] = ch;
                        if (!quiet_mode)
                                debug("%02x ", ch);
                }
        } else {
                if (!quiet_mode)
                        debug("[DMA] ");
                len = d->reg_wo[NCR_TCL] + d->reg_wo[NCR_TCM] * 256;
                if (len == 0)
                        len = 65536;

                scsi_transfer_allocbuf(&d->xferp->cmd_len,
                    &d->xferp->cmd, len, 0);

                for (i=0; i<len; i++) {
                        int ofs = d->dma_address_reg + i;
                        ch = d->dma[ofs & (ASC_DMA_SIZE-1)];
                        d->xferp->cmd[i] = ch;
                        if (!quiet_mode)
                                debug("%02x ", ch);
                }

                d->reg_ro[NCR_TCL] = len & 255;
                d->reg_ro[NCR_TCM] = (len >> 8) & 255;

                d->reg_ro[NCR_STAT] |= NCRSTAT_TC;
        }

        /*
         *  Call the SCSI device to perform the command:
         */
        ok = diskimage_scsicommand(cpu, to_id, DISKIMAGE_SCSI, d->xferp);


        /*  Cause an interrupt:  */
        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
        d->reg_ro[NCR_INTR] |= NCRINTR_FC;
        d->reg_ro[NCR_INTR] |= NCRINTR_BS;

        if (ok == 2)
                d->cur_phase = PHASE_DATA_OUT;
        else if (d->xferp->data_in != NULL)
                d->cur_phase = PHASE_DATA_IN;
        else
                d->cur_phase = PHASE_STATUS;

        d->reg_ro[NCR_STAT] = (d->reg_ro[NCR_STAT] & ~7) | d->cur_phase;
        d->reg_ro[NCR_STEP] = (d->reg_ro[NCR_STEP] & ~7) | 4;   /*  DONE (?)  */

        if (!quiet_mode)
                debug("}");

        return ok;
}


DEVICE_ACCESS(asc_address_reg)
{
        struct asc_data *d = extra;

        if (relative_addr + len > 4)
                return 0;

        if (writeflag==MEM_READ) {
                memcpy(data, d->dma_address_reg_memory + relative_addr, len);
        } else {
                memcpy(d->dma_address_reg_memory + relative_addr, data, len);
        }

        return 1;
}


DEVICE_ACCESS(asc_dma)
{
        struct asc_data *d = extra;

        if (writeflag==MEM_READ) {
                memcpy(data, d->dma + relative_addr, len);
#ifdef ASC_DEBUG
                {
                        int i;
                        debug("[ asc: read from DMA addr 0x%05x:",
                            (int) relative_addr);
                        for (i=0; i<len; i++)
                                debug(" %02x", data[i]);
                        debug(" ]\n");
                }
#endif

                /*  Don't return the common way, as that
                    would overwrite data.  */
                return 1;
        } else {
                memcpy(d->dma + relative_addr, data, len);
#ifdef ASC_DEBUG
                {
                        int i;
                        debug("[ asc: write to  DMA addr 0x%05x:",
                            (int) relative_addr);
                        for (i=0; i<len; i++)
                                debug(" %02x", data[i]);
                        debug(" ]\n");
                }
#endif
                /*  Quick return.  */
                return 1;
        }
}


DEVICE_ACCESS(asc)
{
        int regnr;
        struct asc_data *d = extra;
        int target_exists;
        int n_messagebytes = 0;
        uint64_t idata = 0, odata = 0;

        if (writeflag == MEM_WRITE)
                idata = memory_readmax64(cpu, data, len);

#if 0
        /*  Debug stuff useful when trying to make dev_asc compatible
            with the 'arc' emulation mode, which is different from
            the DECstation mode.  */
        fatal("[ asc: writeflag=%i addr=%08x idata=%016llx ]\n",
            writeflag, (int)relative_addr, (long long)idata);
#endif

        switch (d->mode) {
        case DEV_ASC_DEC:
                regnr = relative_addr / 4;
                break;
        case DEV_ASC_PICA:
        default:
                regnr = relative_addr;
        }

        /*  Controller's ID is fixed:  */
        d->reg_ro[NCR_CFG1] = (d->reg_ro[NCR_CFG1] & ~7) | ASC_SCSI_ID;

        d->reg_ro[NCR_FFLAG] = ((d->reg_ro[NCR_STEP] & 0x7) << 5)
            + d->n_bytes_in_fifo;

        d->dma_address_reg =
            d->dma_address_reg_memory[0] +
            (d->dma_address_reg_memory[1] << 8) +
            (d->dma_address_reg_memory[2] << 16) +
            (d->dma_address_reg_memory[3] << 24);

        if (regnr < 0x10) {
                if (regnr == NCR_FIFO) {
                        if (writeflag == MEM_WRITE)
                                dev_asc_fifo_write(d, idata);
                        else
                                odata = dev_asc_fifo_read(d);
                } else {
                        if (writeflag==MEM_WRITE)
                                d->reg_wo[regnr] = idata;
                        else
                                odata = d->reg_ro[regnr];
                }

#ifdef ASC_FULL_REGISTER_ACCESS_DEBUG
                if (!quiet_mode) {
                        if (writeflag==MEM_READ) {
                                debug("[ asc: read from %s: 0x%02x",
                                    asc_reg_names[regnr], (int)odata);
                        } else {
                                debug("[ asc: write to  %s: 0x%02x",
                                    asc_reg_names[regnr], (int)idata);
                        }
                }
#endif
        } else if (relative_addr >= 0x300 && relative_addr < 0x600
            && d->turbochannel != NULL) {
                debug("[ asc: offset 0x%x, redirecting to turbochannel"
                    " access ]\n", relative_addr);
                return dev_turbochannel_access(cpu, mem,
                    relative_addr, data, len, writeflag,
                    d->turbochannel);
        } else {
                if (writeflag==MEM_READ) {
                        fatal("[ asc: read from 0x%04x: 0x%02x ]\n",
                            relative_addr, (int)odata);
                } else {
                        fatal("[ asc: write to  0x%04x: 0x%02x ]\n",
                            relative_addr, (int)idata);
                }
        }

        /*
         *  Some registers are read/write. Copy contents of
         *  reg_wo to reg_ro:
         */
#if 0
        d->reg_ro[ 0] = d->reg_wo[0];   /*  Transfer count lo and  */
        d->reg_ro[ 1] = d->reg_wo[1];   /*  middle  */
#endif
        d->reg_ro[ 2] = d->reg_wo[2];
        d->reg_ro[ 3] = d->reg_wo[3];
        d->reg_ro[ 8] = d->reg_wo[8];
        d->reg_ro[ 9] = d->reg_wo[9];
        d->reg_ro[10] = d->reg_wo[10];
        d->reg_ro[11] = d->reg_wo[11];
        d->reg_ro[12] = d->reg_wo[12];

        if (regnr == NCR_CMD && writeflag == MEM_WRITE) {
                if (!quiet_mode)
                        debug(" ");

                /*  TODO:  Perhaps turn off others here too?  */
                d->reg_ro[NCR_INTR] &= ~NCRINTR_SBR;

                if (idata & NCRCMD_DMA) {
                        if (!quiet_mode)
                                debug("[DMA] ");

                        /*
                         *  DMA commands load the transfer count from the
                         *  write-only registers to the read-only ones, and
                         *  the Terminal Count bit is cleared.
                         */
                        d->reg_ro[NCR_TCL] = d->reg_wo[NCR_TCL];
                        d->reg_ro[NCR_TCM] = d->reg_wo[NCR_TCM];
                        d->reg_ro[NCR_TCH] = d->reg_wo[NCR_TCH];
                        d->reg_ro[NCR_STAT] &= ~NCRSTAT_TC;
                }

                switch (idata & ~NCRCMD_DMA) {

                case NCRCMD_NOP:
                        if (!quiet_mode)
                                debug("NOP");
                        break;

                case NCRCMD_FLUSH:
                        if (!quiet_mode)
                                debug("FLUSH");
                        /*  Flush the FIFO:  */
                        dev_asc_fifo_flush(d);
                        break;

                case NCRCMD_RSTCHIP:
                        if (!quiet_mode)
                                debug("RSTCHIP");
                        /*  Hardware reset.  */
                        dev_asc_reset(d);
                        break;

                case NCRCMD_RSTSCSI:
                        if (!quiet_mode)
                                debug("RSTSCSI");
                        /*  No interrupt if interrupts are disabled.  */
                        if (!(d->reg_wo[NCR_CFG1] & NCRCFG1_SRR))
                                d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                        d->reg_ro[NCR_INTR] |= NCRINTR_SBR;
                        d->reg_ro[NCR_INTR] |= NCRINTR_FC;
                        d->cur_state = STATE_DISCONNECTED;
                        break;

                case NCRCMD_ENSEL:
                        if (!quiet_mode)
                                debug("ENSEL");
                        /*  TODO  */
                        break;

                case NCRCMD_ICCS:
                        if (!quiet_mode)
                                debug("ICCS");
                        /*  Reveice a status byte + a message byte.  */

                        /*  TODO: how about other status and message bytes?  */
                        if (d->xferp != NULL && d->xferp->status != NULL)
                                dev_asc_fifo_write(d, d->xferp->status[0]);
                        else
                                dev_asc_fifo_write(d, 0x00);

                        if (d->xferp != NULL && d->xferp->msg_in != NULL)
                                dev_asc_fifo_write(d, d->xferp->msg_in[0]);
                        else
                                dev_asc_fifo_write(d, 0x00);

                        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                        d->reg_ro[NCR_INTR] |= NCRINTR_FC;
/*                      d->reg_ro[NCR_INTR] |= NCRINTR_BS; */
                        d->reg_ro[NCR_STAT] = (d->reg_ro[NCR_STAT] & ~7) | 7;
                                /*  ? probably 7  */
                        d->reg_ro[NCR_STEP] = (d->reg_ro[NCR_STEP] & ~7) | 4;
                                /*  ?  */
                        break;

                case NCRCMD_MSGOK:
                        /*  Message is being Rejected if ATN is set,
                            otherwise Accepted.  */
                        if (!quiet_mode) {
                                debug("MSGOK");
                                if (d->atn)
                                        debug("; Rejecting message");
                                else
                                        debug("; Accepting message");
                        }
                        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                        d->reg_ro[NCR_INTR] |= NCRINTR_DIS;

                        d->reg_ro[NCR_STAT] = (d->reg_ro[NCR_STAT] & ~7) |
                            d->cur_phase;       /*  6?  */
                        d->reg_ro[NCR_STEP] = (d->reg_ro[NCR_STEP] & ~7) |
                            4;  /*  ?  */

                        d->cur_state = STATE_DISCONNECTED;

                        if (d->xferp != NULL)
                                scsi_transfer_free(d->xferp);
                        d->xferp = NULL;
                        break;

                case NCRCMD_SETATN:
                        if (!quiet_mode)
                                debug("SETATN");
                        d->atn = 1;
                        break;

                case NCRCMD_RSTATN:
                        if (!quiet_mode)
                                debug("RSTATN");
                        d->atn = 0;
                        break;

                case NCRCMD_SELNATN:
                case NCRCMD_SELATN:
                case NCRCMD_SELATNS:
                case NCRCMD_SELATN3:
                        d->cur_phase = PHASE_COMMAND;
                        switch (idata & ~NCRCMD_DMA) {
                        case NCRCMD_SELATN:
                        case NCRCMD_SELATNS:
                                if ((idata & ~NCRCMD_DMA) == NCRCMD_SELATNS) {
                                        if (!quiet_mode)
                                                debug("SELATNS: select with "
                                                    "atn and stop, id %i",
                                                    d->reg_wo[NCR_SELID] & 7);
                                        d->cur_phase = PHASE_MSG_OUT;
                                } else {
                                        if (!quiet_mode)
                                                debug("SELATN: select with atn"
                                                    ", id %i",
                                                    d->reg_wo[NCR_SELID] & 7);
                                }
                                n_messagebytes = 1;
                                break;
                        case NCRCMD_SELATN3:
                                if (!quiet_mode)
                                        debug("SELNATN: select with atn3, "
                                            "id %i", d->reg_wo[NCR_SELID] & 7);
                                n_messagebytes = 3;
                                break;
                        case NCRCMD_SELNATN:
                                if (!quiet_mode)
                                        debug("SELNATN: select without atn, "
                                            "id %i", d->reg_wo[NCR_SELID] & 7);
                                n_messagebytes = 0;
                        }

                        /*  TODO: not just disk, but some generic
                            SCSI device  */
                        target_exists = diskimage_exist(cpu->machine,
                            d->reg_wo[NCR_SELID] & 7, DISKIMAGE_SCSI);

                        if (target_exists) {
                                /*
                                 *  Select a SCSI device, send message bytes
                                 *  (if any) and command bytes to the target.
                                 */
                                int ok;

                                dev_asc_newxfer(d);

                                ok = dev_asc_select(cpu, d,
                                    d->reg_ro[NCR_CFG1] & 7,
                                    d->reg_wo[NCR_SELID] & 7,
                                    idata & NCRCMD_DMA? 1 : 0,
                                    n_messagebytes);

                                if (ok)
                                        d->cur_state = STATE_INITIATOR;
                                else {
                                        d->cur_state = STATE_DISCONNECTED;
                                        d->reg_ro[NCR_INTR] |= NCRINTR_DIS;
                                        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                                        d->reg_ro[NCR_STEP] =
                                            (d->reg_ro[NCR_STEP] & ~7) | 0;
                                        if (d->xferp != NULL)
                                                scsi_transfer_free(d->xferp);
                                        d->xferp = NULL;
                                }
                        } else {
                                /*
                                 *  Selection failed, non-existant scsi ID:
                                 *
                                 *  This is good enough to fool Ultrix, NetBSD,
                                 *  OpenBSD and Linux to continue detection of
                                 *  other IDs, without giving any warnings.
                                 */
                                d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                                d->reg_ro[NCR_INTR] |= NCRINTR_DIS;
                                d->reg_ro[NCR_STEP] &= ~7;
                                d->reg_ro[NCR_STEP] |= 0;
                                dev_asc_fifo_flush(d);
                                d->cur_state = STATE_DISCONNECTED;
                        }
                        break;

                case NCRCMD_TRPAD:
                        if (!quiet_mode)
                                debug("TRPAD");

                        dev_asc_newxfer(d);
                        {
                                int ok;

                                ok = dev_asc_transfer(cpu, d,
                                    idata & NCRCMD_DMA? 1 : 0);
                                if (!ok) {
                                        d->cur_state = STATE_DISCONNECTED;
                                        d->reg_ro[NCR_INTR] |= NCRINTR_DIS;
                                        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                                        d->reg_ro[NCR_STEP] = (d->reg_ro[
                                            NCR_STEP] & ~7) | 0;
                                        if (d->xferp != NULL)
                                                scsi_transfer_free(d->xferp);
                                        d->xferp = NULL;
                                }
                        }
break;

/*  Old code which didn't work with Mach:  */
#if 0
                        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                        d->reg_ro[NCR_INTR] |= NCRINTR_BS;
                        d->reg_ro[NCR_INTR] |= NCRINTR_FC;
                        d->reg_ro[NCR_STAT] |= NCRSTAT_TC;

                        d->reg_ro[NCR_TCL] = 0;
                        d->reg_ro[NCR_TCM] = 0;

                        d->reg_ro[NCR_STEP] &= ~7;
#if 0
                        d->reg_ro[NCR_STEP] |= 0;
                        dev_asc_fifo_flush(d);
#else
                        d->reg_ro[NCR_STEP] |= 4;
#endif
                        break;
#endif

                case NCRCMD_TRANS:
                        if (!quiet_mode)
                                debug("TRANS");

                        {
                                int ok;

                                ok = dev_asc_transfer(cpu, d,
                                    idata & NCRCMD_DMA? 1 : 0);
                                if (!ok) {
                                        d->cur_state = STATE_DISCONNECTED;
                                        d->reg_ro[NCR_INTR] |= NCRINTR_DIS;
                                        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                                        d->reg_ro[NCR_STEP] = (d->reg_ro[
                                            NCR_STEP] & ~7) | 0;
                                        if (d->xferp != NULL)
                                                scsi_transfer_free(d->xferp);
                                        d->xferp = NULL;
                                }
                        }
                        break;

                default:
                        fatal("(unimplemented asc cmd 0x%02x)", (int)idata);
                        d->reg_ro[NCR_STAT] |= NCRSTAT_INT;
                        d->reg_ro[NCR_INTR] |= NCRINTR_ILL;
                        /*
                         *  TODO:  exit or continue with Illegal command
                         *  interrupt?
                         */
                        exit(1);
                }
        }

        if (regnr == NCR_INTR && writeflag == MEM_READ) {
                /*
                 *  Reading the interrupt register de-asserts the
                 *  interrupt pin.  Also, INTR, STEP, and STAT are all
                 *  cleared, according to page 64 of the LSI53CF92A manual,
                 *  if "interrupt output is true".
                 */
                if (d->reg_ro[NCR_STAT] & NCRSTAT_INT) {
                        d->reg_ro[NCR_INTR] = 0;
                        d->reg_ro[NCR_STEP] = 0;
                        d->reg_ro[NCR_STAT] = 0;

                        /*  For Mach/PMAX? TODO  */
                        d->reg_ro[NCR_STAT] = PHASE_COMMAND;
                }

                cpu_interrupt_ack(cpu, d->irq_nr);
        }

        if (regnr == NCR_CFG1) {
                /*  TODO: other bits  */
                if (!quiet_mode) {
                        debug(" parity %s,", d->reg_ro[regnr] &
                            NCRCFG1_PARENB? "enabled" : "disabled");
                        debug(" scsi_id %i", d->reg_ro[regnr] & 0x7);
                }
        }

#ifdef ASC_FULL_REGISTER_ACCESS_DEBUG
        debug(" ]\n");
#endif
        dev_asc_tick(cpu, extra);

        if (writeflag == MEM_READ)
                memory_writemax64(cpu, data, len, odata);

        return 1;
}


/*
 *  dev_asc_init():
 *
 *  Register an 'asc' device.
 */
void dev_asc_init(struct machine *machine, struct memory *mem,
        uint64_t baseaddr, int irq_nr, void *turbochannel,
        int mode,
        size_t (*dma_controller)(void *dma_controller_data,
                unsigned char *data, size_t len, int writeflag),
        void *dma_controller_data)
{
        struct asc_data *d;

        d = malloc(sizeof(struct asc_data));
        if (d == NULL) {
                fprintf(stderr, "out of memory\n");
                exit(1);
        }
        memset(d, 0, sizeof(struct asc_data));
        d->irq_nr       = irq_nr;
        d->turbochannel = turbochannel;
        d->mode         = mode;

        d->reg_ro[NCR_CFG3] = NCRF9XCFG3_CDB;

        d->dma_address_reg_memory = malloc(machine->arch_pagesize);
        d->dma = malloc(ASC_DMA_SIZE);
        if (d->dma == NULL || d->dma_address_reg_memory == NULL) {
                fprintf(stderr, "out of memory\n");
                exit(1);
        }
        memset(d->dma_address_reg_memory, 0, machine->arch_pagesize);
        memset(d->dma, 0, ASC_DMA_SIZE);

        d->dma_controller      = dma_controller;
        d->dma_controller_data = dma_controller_data;

        memory_device_register(mem, "asc", baseaddr,
            mode == DEV_ASC_PICA? DEV_ASC_PICA_LENGTH : DEV_ASC_DEC_LENGTH,
            dev_asc_access, d, DM_DEFAULT, NULL);

        if (mode == DEV_ASC_DEC) {
                memory_device_register(mem, "asc_dma_address_reg",
                    baseaddr + 0x40000, 4096, dev_asc_address_reg_access, d,
                    DM_DYNTRANS_OK | DM_DYNTRANS_WRITE_OK,
                    (unsigned char *)&d->dma_address_reg_memory[0]);
                memory_device_register(mem, "asc_dma", baseaddr + 0x80000,
                    ASC_DMA_SIZE, dev_asc_dma_access, d,
                    DM_DYNTRANS_OK | DM_DYNTRANS_WRITE_OK, d->dma);
        }

        machine_add_tickfunction(machine, dev_asc_tick, d, ASC_TICK_SHIFT, 0.0);
}
