path: root/src/hdc.c

/*
  Hatari - hdc.c

  This file is distributed under the GNU General Public License, version 2
  or at your option any later version. Read the file gpl.txt for details.

  Low-level hard drive emulation
*/
const char HDC_fileid[] = "Hatari hdc.c";

#include <errno.h>
#include <SDL_endian.h>

#include "main.h"
#include "configuration.h"
#include "debugui.h"
#include "file.h"
#include "fdc.h"
#include "hdc.h"
#include "ioMem.h"
#include "log.h"
#include "memorySnapShot.h"
#include "mfp.h"
#include "ncr5380.h"
#include "stMemory.h"
#include "tos.h"
#include "statusbar.h"


/*
  ACSI emulation: 
  ACSI commands are six byte-packets sent to the
  hard drive controller (which is on the HD unit, not in the ST)

  While the hard drive is busy, DRQ is high, polling the DRQ during
  operation interrupts the current operation. The DRQ status can
  be polled non-destructively in GPIP.

  (For simplicity, the operation is finished immediately,
  this is a potential bug, but I doubt it is significant,
  we just appear to have a very fast hard drive.)

  The ACSI command set is a subset of the SCSI standard.
  (for details, see the X3T9.2 SCSI draft documents
  from 1985, for an example of writing ACSI commands,
  see the TOS DMA boot code) 
*/

// #define DISALLOW_HDC_WRITE
// #define HDC_VERBOSE           /* display operations */

#define HDC_ReadInt16(a, i) (((unsigned) a[i] << 8) | a[i + 1])
#define HDC_ReadInt24(a, i) (((unsigned) a[i] << 16) | ((unsigned) a[i + 1] << 8) | a[i + 2])
#define HDC_ReadInt32(a, i) (((unsigned) a[i] << 24) | ((unsigned) a[i + 1] << 16) | ((unsigned) a[i + 2] << 8) | a[i + 3])

/* HDC globals */
static SCSI_CTRLR AcsiBus;
int nAcsiPartitions;
bool bAcsiEmuOn;

/* Our dummy INQUIRY response data */
static unsigned char inquiry_bytes[] =
{
	0,                /* device type 0 = direct access device */
	0,                /* device type qualifier (nonremovable) */
	1,                /* ACSI/SCSI version */
	0,                /* reserved */
	31,               /* length of the following data */
	0, 0, 0,          /* Vendor specific data */
	'H','a','t','a','r','i',' ',' ',    /* Vendor ID */
	'E','m','u','l','a','t','e','d',    /* Product ID 1 */
	'H','a','r','d','d','i','s','k',    /* Product ID 2 */
	'0','1','8','0',                    /* Revision */
};


/*---------------------------------------------------------------------*/
/**
 * Return the LUN (logical unit number) specified in the current
 * ACSI/SCSI command block.
 */
static unsigned char HDC_GetLUN(SCSI_CTRLR *ctr)
{
	return (ctr->command[1] & 0xE0) >> 5;
}

/**
 * Return the start sector (logical block address) specified in the
 * current ACSI/SCSI command block.
 */
static unsigned long HDC_GetLBA(SCSI_CTRLR *ctr)
{
	/* offset = logical block address * physical sector size */
	if (ctr->opcode < 0x20)				/* Class 0? */
		return HDC_ReadInt24(ctr->command, 1) & 0x1FFFFF;
	else
		return HDC_ReadInt32(ctr->command, 2);	/* Class 1 */
}

/**
 * Return number of bytes for a command block.
 */
static int HDC_GetCommandByteCount(SCSI_CTRLR *ctr)
{
	if (ctr->opcode == 0x88 || ctr->opcode == 0x8a || ctr->opcode == 0x8f ||
		ctr->opcode == 0x91 || ctr->opcode == 0x9e || ctr->opcode == 0x9f) {
		return 16;
	}
	else if (ctr->opcode == 0xa0) {
		return 12;
	}
	else if (ctr->opcode == 0x05 || (ctr->opcode >= 0x20 && ctr->opcode <= 0x7d)) {
		return 10;
	} else {
		return 6;
	}
}


/**
 * Return the count specified in the current ACSI command block.
 */
static int HDC_GetCount(SCSI_CTRLR *ctr)
{
	if (ctr->opcode < 0x20)
		return ctr->command[4];			/* Class 0 */
	else
		return HDC_ReadInt16(ctr->command, 7);	/* Class 1 */
}

/**
 * Get pointer to response buffer, set up size indicator - and allocate
 * a new buffer if it is not big enough
 */
static Uint8 *HDC_PrepRespBuf(SCSI_CTRLR *ctr, int size)
{
	ctr->data_len = size;
	ctr->offset = 0;

	if (size > ctr->buffer_size)
	{
		ctr->buffer_size = size;
		ctr->buffer = realloc(ctr->buffer, size);
	}

	return ctr->buffer;
}

/**
 * Get info string for SCSI/ACSI command packets.
 */
static inline char *HDC_CmdInfoStr(SCSI_CTRLR *ctr)
{
	char cdb[80] = { 0 };

	for (int i = 0; i < HDC_GetCommandByteCount(ctr); i++) {
		char tmp[5];
		snprintf(tmp, sizeof(tmp), "%s%02x", i ? ":" : "", ctr->command[i]);
		strcat(cdb, tmp);
	}

	static char str[160];

	snprintf(str, sizeof(str), "%s, t=%i, lun=%i, cdb=%s",
                 ctr->typestr, ctr->target, HDC_GetLUN(ctr), cdb);

	return str;
}


/**
 * Seek - move to a sector
 */
static void HDC_Cmd_Seek(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];

	dev->nLastBlockAddr = HDC_GetLBA(ctr);

	LOG_TRACE(TRACE_SCSI_CMD, "HDC: SEEK (%s), LBA=%i",
	          HDC_CmdInfoStr(ctr), dev->nLastBlockAddr);

	if (dev->nLastBlockAddr < dev->hdSize &&
	    fseeko(dev->image_file, (off_t)dev->nLastBlockAddr * dev->blockSize, SEEK_SET) == 0)
	{
		LOG_TRACE(TRACE_SCSI_CMD, " -> OK\n");
		ctr->status = HD_STATUS_OK;
		dev->nLastError = HD_REQSENS_OK;
	}
	else
	{
		LOG_TRACE(TRACE_SCSI_CMD, " -> ERROR\n");
		ctr->status = HD_STATUS_ERROR;
		dev->nLastError = HD_REQSENS_INVADDR;
	}

	dev->bSetLastBlockAddr = true;
}


/**
 * Inquiry - return some disk information
 */
static void HDC_Cmd_Inquiry(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];
	Uint8 *buf;
	int count;

	count = HDC_GetCount(ctr);

	LOG_TRACE(TRACE_SCSI_CMD, "HDC: INQUIRY (%s)\n", HDC_CmdInfoStr(ctr));

	buf = HDC_PrepRespBuf(ctr, count);
	if (count > (int)sizeof(inquiry_bytes))
	{
		memset(&buf[sizeof(inquiry_bytes)], 0, count - sizeof(inquiry_bytes));
		count = sizeof(inquiry_bytes);
	}
	memcpy(buf, inquiry_bytes, count);

	/* For unsupported LUNs set the Peripheral Qualifier and the
	 * Peripheral Device Type according to the SCSI standard */
	buf[0] = HDC_GetLUN(ctr) == 0 ? 0 : 0x7F;

	buf[4] = count - 5;

	ctr->status = HD_STATUS_OK;

	dev->nLastError = HD_REQSENS_OK;
	dev->bSetLastBlockAddr = false;
}


/**
 * Request sense - return some disk information
 */
static void HDC_Cmd_RequestSense(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];
	int nRetLen;
	Uint8 *retbuf;

	nRetLen = HDC_GetCount(ctr);

	LOG_TRACE(TRACE_SCSI_CMD, "HDC: REQUEST SENSE (%s).\n", HDC_CmdInfoStr(ctr));

	if ((nRetLen < 4 && nRetLen != 0) || nRetLen > 22)
	{
		Log_Printf(LOG_WARN, "HDC: *** Strange REQUEST SENSE ***!\n");
	}

	/* Limit to sane length */
	if (nRetLen <= 0)
	{
		nRetLen = 4;
	}
	else if (nRetLen > 22)
	{
		nRetLen = 22;
	}

	retbuf = HDC_PrepRespBuf(ctr, nRetLen);
	memset(retbuf, 0, nRetLen);

	if (nRetLen <= 4)
	{
		retbuf[0] = dev->nLastError;
		if (dev->bSetLastBlockAddr)
		{
			retbuf[0] |= 0x80;
			retbuf[1] = dev->nLastBlockAddr >> 16;
			retbuf[2] = dev->nLastBlockAddr >> 8;
			retbuf[3] = dev->nLastBlockAddr;
		}
	}
	else
	{
		retbuf[0] = 0x70;
		if (dev->bSetLastBlockAddr)
		{
			retbuf[0] |= 0x80;
			retbuf[4] = dev->nLastBlockAddr >> 16;
			retbuf[5] = dev->nLastBlockAddr >> 8;
			retbuf[6] = dev->nLastBlockAddr;
		}
		switch (dev->nLastError)
		{
		 case HD_REQSENS_OK:  retbuf[2] = 0; break;
		 case HD_REQSENS_OPCODE:  retbuf[2] = 5; break;
		 case HD_REQSENS_INVADDR:  retbuf[2] = 5; break;
		 case HD_REQSENS_INVARG:  retbuf[2] = 5; break;
		 case HD_REQSENS_INVLUN:  retbuf[2] = 5; break;
		 default: retbuf[2] = 4; break;
		}
		retbuf[7] = 14;
		retbuf[12] = dev->nLastError;
		retbuf[19] = dev->nLastBlockAddr >> 16;
		retbuf[20] = dev->nLastBlockAddr >> 8;
		retbuf[21] = dev->nLastBlockAddr;
	}

	/*
	fprintf(stderr,"*** Requested sense packet:\n");
	int i;
	for (i = 0; i<nRetLen; i++) fprintf(stderr,"%2x ",retbuf[i]);
	fprintf(stderr,"\n");
	*/

	ctr->status = HD_STATUS_OK;
}


/**
 * Mode sense - Vendor specific page 00h.
 * (Just enough to make the HDX tool from AHDI 5.0 happy)
 */
static void HDC_CmdModeSense0x00(SCSI_DEV *dev, SCSI_CTRLR *ctr, Uint8 *buf)
{
	buf[0] = 0;
	buf[1] = 14;
	buf[2] = 0;
	buf[3] = 8;
	buf[4] = 0;

	buf[5] = dev->hdSize >> 16;  // Number of blocks, high
	buf[6] = dev->hdSize >> 8;   // Number of blocks, med
	buf[7] = dev->hdSize;        // Number of blocks, low

	buf[8] = 0;

	buf[9] = 0;      // Block size in bytes, high
	buf[10] = 2;     // Block size in bytes, med
	buf[11] = 0;     // Block size in bytes, low

	buf[12] = 0;
	buf[13] = 0;
	buf[14] = 0;
	buf[15] = 0;
}


/**
 * Mode sense - Rigid disk geometry page (requested by ASV).
 */
static void HDC_CmdModeSense0x04(SCSI_DEV *dev, SCSI_CTRLR *ctr, Uint8 *buf)
{
	buf[0] = 4;
	buf[1] = 22;

	buf[2] = dev->hdSize >> 23;  // Number of cylinders, high
	buf[3] = dev->hdSize >> 15;  // Number of cylinders, med
	buf[4] = dev->hdSize >> 7;   // Number of cylinders, low

	buf[5] = 128;    // Number of heads

	buf[6] = 0;
	buf[7] = 0;
	buf[8] = 0;

	buf[9] = 0;
	buf[10] = 0;
	buf[11] = 0;

	buf[12] = 0;
	buf[13] = 0;

	buf[14] = 0;
	buf[15] = 0;
	buf[16] = 0;

	buf[17] = 0;

	buf[18] = 0;

	buf[19] = 0;

	buf[20] = 0;
	buf[21] = 0;

	buf[22] = 0;
	buf[23] = 0;
}


/**
 * Mode sense - Get parameters from disk.
 */
static void HDC_Cmd_ModeSense(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];

	LOG_TRACE(TRACE_SCSI_CMD, "HDC: MODE SENSE (%s).\n", HDC_CmdInfoStr(ctr));

	dev->bSetLastBlockAddr = false;

	switch(ctr->command[2])
	{
        case 0x00: {
		Uint8 *buf = HDC_PrepRespBuf(ctr, 16);
		HDC_CmdModeSense0x00(dev, ctr, buf);
		break;
	}

        case 0x04: {
		Uint8 *buf = HDC_PrepRespBuf(ctr, 24);
		HDC_CmdModeSense0x04(dev, ctr, buf);
		break;
	}

        case 0x3f: {
		Uint8 *buf = HDC_PrepRespBuf(ctr, 44);
		buf[0] = 44;
		HDC_CmdModeSense0x04(dev, ctr, buf + 4);
		HDC_CmdModeSense0x00(dev, ctr, buf + 28);
		break;
	}

        default:
		Log_Printf(LOG_TODO, "HDC: Unsupported MODE SENSE command\n");
		ctr->status = HD_STATUS_ERROR;
		dev->nLastError = HD_REQSENS_INVARG;
		return;
	}

	ctr->status = HD_STATUS_OK;
	dev->nLastError = HD_REQSENS_OK;
}


/**
 * Format drive.
 */
static void HDC_Cmd_FormatDrive(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];

	LOG_TRACE(TRACE_SCSI_CMD, "HDC: FORMAT DRIVE (%s).\n", HDC_CmdInfoStr(ctr));

	/* Should erase the whole image file here... */

	ctr->status = HD_STATUS_OK;
	dev->nLastError = HD_REQSENS_OK;
	dev->bSetLastBlockAddr = false;
}


/**
 * Report LUNs.
 */
static void HDC_Cmd_ReportLuns(SCSI_CTRLR *ctr)
{
        SCSI_DEV *dev = &ctr->devs[ctr->target];
	Uint8 *buf;

        LOG_TRACE(TRACE_SCSI_CMD, "HDC: REPORT LUNS (%s).\n", HDC_CmdInfoStr(ctr));

        buf = HDC_PrepRespBuf(ctr, 16);

	// LUN list length, 8 bytes per LUN
	buf[0] = 0;
	buf[1] = 0;
	buf[2] = 0;
	buf[3] = 8;
	memset(&buf[4], 0, 12);

        ctr->status = HD_STATUS_OK;
        dev->nLastError = HD_REQSENS_OK;
        dev->bSetLastBlockAddr = false;
}


/**
 * Read capacity of our disk.
 */
static void HDC_Cmd_ReadCapacity(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];
	int nSectors = dev->hdSize - 1;
	Uint8 *buf;

	LOG_TRACE(TRACE_SCSI_CMD, "HDC: READ CAPACITY (%s)\n", HDC_CmdInfoStr(ctr));

	buf = HDC_PrepRespBuf(ctr, 8);

	buf[0] = (nSectors >> 24) & 0xFF;
	buf[1] = (nSectors >> 16) & 0xFF;
	buf[2] = (nSectors >> 8) & 0xFF;
	buf[3] = nSectors & 0xFF;
	buf[4] = (dev->blockSize >> 24) & 0xFF;
	buf[5] = (dev->blockSize >> 16) & 0xFF;
	buf[6] = (dev->blockSize >> 8) & 0xFF;
	buf[7] = dev->blockSize & 0xFF;

	ctr->status = HD_STATUS_OK;
	dev->nLastError = HD_REQSENS_OK;
	dev->bSetLastBlockAddr = false;
}


/**
 * Write a sector off our disk - (seek implied)
 */
static void HDC_Cmd_WriteSector(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];

	dev->nLastBlockAddr = HDC_GetLBA(ctr);

	LOG_TRACE(TRACE_SCSI_CMD, "HDC: WRITE SECTOR (%s) with LBA 0x%x",
	          HDC_CmdInfoStr(ctr), dev->nLastBlockAddr);

	/* seek to the position */
	if (dev->nLastBlockAddr >= dev->hdSize ||
	    fseeko(dev->image_file, (off_t)dev->nLastBlockAddr * dev->blockSize, SEEK_SET) != 0)
	{
		ctr->status = HD_STATUS_ERROR;
		dev->nLastError = HD_REQSENS_INVADDR;
	}
	else
	{
		ctr->data_len = HDC_GetCount(ctr) * dev->blockSize;
		if (ctr->data_len)
		{
			HDC_PrepRespBuf(ctr, ctr->data_len);
			ctr->dmawrite_to_fh = dev->image_file;
			ctr->status = HD_STATUS_OK;
			dev->nLastError = HD_REQSENS_OK;
		}
		else
		{
			ctr->status = HD_STATUS_ERROR;
			dev->nLastError = HD_REQSENS_WRITEERR;
		}
	}
	LOG_TRACE(TRACE_SCSI_CMD, " -> %s (%d)\n",
		  ctr->status == HD_STATUS_OK ? "OK" : "ERROR",
		  dev->nLastError);

	dev->bSetLastBlockAddr = true;
}


/**
 * Read a sector off our disk - (implied seek)
 */
static void HDC_Cmd_ReadSector(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];
	Uint8 *buf;
	int n;

	dev->nLastBlockAddr = HDC_GetLBA(ctr);

	LOG_TRACE(TRACE_SCSI_CMD, "HDC: READ SECTOR (%s) with LBA 0x%x",
	          HDC_CmdInfoStr(ctr), dev->nLastBlockAddr);

	/* seek to the position */
	if (dev->nLastBlockAddr >= dev->hdSize ||
	    fseeko(dev->image_file, (off_t)dev->nLastBlockAddr * dev->blockSize, SEEK_SET) != 0)
	{
		ctr->status = HD_STATUS_ERROR;
		dev->nLastError = HD_REQSENS_INVADDR;
	}
	else
	{
		buf = HDC_PrepRespBuf(ctr, dev->blockSize * HDC_GetCount(ctr));
		n = fread(buf, dev->blockSize, HDC_GetCount(ctr), dev->image_file);
		if (n == HDC_GetCount(ctr))
		{
			ctr->status = HD_STATUS_OK;
			dev->nLastError = HD_REQSENS_OK;
		}
		else
		{
			ctr->status = HD_STATUS_ERROR;
			dev->nLastError = HD_REQSENS_NOSECTOR;
		}
	}
	LOG_TRACE(TRACE_SCSI_CMD, " -> %s (%d)\n",
		  ctr->status == HD_STATUS_OK ? "OK" : "ERROR",
		  dev->nLastError);

	dev->bSetLastBlockAddr = true;
}


/**
 * Test unit ready
 */
static void HDC_Cmd_TestUnitReady(SCSI_CTRLR *ctr)
{
	LOG_TRACE(TRACE_SCSI_CMD, "HDC: TEST UNIT READY (%s).\n", HDC_CmdInfoStr(ctr));
	ctr->status = HD_STATUS_OK;
}


/**
 * Emulation routine for HDC command packets.
 */
static void HDC_EmulateCommandPacket(SCSI_CTRLR *ctr)
{
	SCSI_DEV *dev = &ctr->devs[ctr->target];

	ctr->data_len = 0;

	switch (ctr->opcode)
	{
	 case HD_TEST_UNIT_RDY:
		HDC_Cmd_TestUnitReady(ctr);
		break;

	 case HD_READ_CAPACITY1:
		HDC_Cmd_ReadCapacity(ctr);
		break;

	 case HD_READ_SECTOR:
	 case HD_READ_SECTOR1:
		HDC_Cmd_ReadSector(ctr);
		break;

	 case HD_WRITE_SECTOR:
	 case HD_WRITE_SECTOR1:
		HDC_Cmd_WriteSector(ctr);
		break;

	 case HD_INQUIRY:
		HDC_Cmd_Inquiry(ctr);
		break;

	 case HD_SEEK:
		HDC_Cmd_Seek(ctr);
		break;

	 case HD_SHIP:
		LOG_TRACE(TRACE_SCSI_CMD, "HDC: SHIP (%s).\n", HDC_CmdInfoStr(ctr));
		ctr->status = 0xFF;
		break;

	 case HD_REQ_SENSE:
		HDC_Cmd_RequestSense(ctr);
		break;

	 case HD_MODESELECT:
		LOG_TRACE(TRACE_SCSI_CMD, "HDC: MODE SELECT (%s) TODO!\n", HDC_CmdInfoStr(ctr));
		ctr->status = HD_STATUS_OK;
		dev->nLastError = HD_REQSENS_OK;
		dev->bSetLastBlockAddr = false;
		break;

	 case HD_MODESENSE:
		HDC_Cmd_ModeSense(ctr);
		break;

	 case HD_FORMAT_DRIVE:
		HDC_Cmd_FormatDrive(ctr);
		break;

	case HD_REPORT_LUNS:
		HDC_Cmd_ReportLuns(ctr);
		break;

	 /* as of yet unsupported commands */
	 case HD_VERIFY_TRACK:
	 case HD_FORMAT_TRACK:
	 case HD_CORRECTION:

	 default:
		LOG_TRACE(TRACE_SCSI_CMD, "HDC: Unsupported command (%s)!\n", HDC_CmdInfoStr(ctr));
		ctr->status = HD_STATUS_ERROR;
		dev->nLastError = HD_REQSENS_OPCODE;
		dev->bSetLastBlockAddr = false;
		break;
	}

	/* Update the led each time a command is processed */
	Statusbar_EnableHDLed( LED_STATE_ON );
}


/*---------------------------------------------------------------------*/
/**
 * Return given image file (primary) partition count.
 * With tracing enabled, print also partition table.
 *
 * Supports both DOS and Atari master boot record partition
 * tables (with 4 entries).
 *
 * Atari partition type names used for checking
 * whether drive is / needs to be byte-swapped:
 *   GEM     GEMDOS partition < 16MB
 *   BGM     GEMDOS partition > 16MB
 *   RAW     No file system
 *   F32     TOS compatible FAT32 partition
 *   LNX     Linux Ext2 partition, not supported by TOS
 *   MIX     Minix partition, not supported by TOS
 *   SWP     Swap partition, not supported by TOS
 *   UNX     ASV (Atari System V) partition, not supported by TOS
 *   XGM     Extended partition
 *
 * Other partition types (listed in XHDI spec):
 *   MAC     MAC HFS partition, not supported by TOS
 *   QWA     Sinclair QL QDOS partition, not supported by TOS
 * (These haven't been found in the wild.)
 *
 * TODO:
 * - Support also Atari ICD (12 entries, at offset 0x156)
 *   and extended partition schemes
 *
 * Linux kernel has code for both:
 *	https://elixir.bootlin.com/linux/v4.0/source/block/partitions/atari.c
 *
 * Extended partition tables are described in AHDI release notes:
 *	https://www.dev-docs.org/docs/htm/search.php?find=AHDI
 */
int HDC_PartitionCount(FILE *fp, const Uint64 tracelevel, int *pIsByteSwapped)
{
	unsigned char *pinfo, bootsector[512];
	Uint32 start, sectors, total = 0;
	int i, parts = 0;
	off_t offset;

	if (!fp)
		return 0;
	offset = ftello(fp);

	if (fseeko(fp, 0, SEEK_SET) != 0
	    || fread(bootsector, sizeof(bootsector), 1, fp) != 1)
	{
		perror("HDC_PartitionCount");
		return 0;
	}

	/* Try to guess whether we've got to swap the image? */
	if (pIsByteSwapped)
	{
		*pIsByteSwapped = (bootsector[0x1fe] == 0xaa && bootsector[0x1ff] == 0x55)
		    || (bootsector[0x1c6] == 'G' && bootsector[0x1c8] == 'M' && bootsector[0x1c9] == 'E')
		    || (bootsector[0x1c6] == 'B' && bootsector[0x1c8] == 'M' && bootsector[0x1c9] == 'G')
		    || (bootsector[0x1c6] == 'X' && bootsector[0x1c8] == 'M' && bootsector[0x1c9] == 'G')
		    || (bootsector[0x1c6] == 'L' && bootsector[0x1c8] == 'X' && bootsector[0x1c9] == 'N')
		    || (bootsector[0x1c6] == 'R' && bootsector[0x1c8] == 'W' && bootsector[0x1c9] == 'A')
		    || (bootsector[0x1c6] == 'F' && bootsector[0x1c8] == '2' && bootsector[0x1c9] == '3')
		    || (bootsector[0x1c6] == 'U' && bootsector[0x1c8] == 'X' && bootsector[0x1c9] == 'N')
		    || (bootsector[0x1c6] == 'M' && bootsector[0x1c8] == 'X' && bootsector[0x1c9] == 'I')
		    || (bootsector[0x1c6] == 'S' && bootsector[0x1c8] == 'P' && bootsector[0x1c9] == 'W');

		if (*pIsByteSwapped)
		{
			for (i = 0; i < (int)sizeof(bootsector); i += 2)
			{
				uint8_t b = bootsector[i];
				bootsector[i] = bootsector[i + 1];
				bootsector[i + 1] = b;
			}
		}
	}

	if (bootsector[0x1FE] == 0x55 && bootsector[0x1FF] == 0xAA)
	{
		int ptype, boot;

		LOG_TRACE(tracelevel, "DOS MBR:\n");
		/* first partition table entry */
		pinfo = bootsector + 0x1BE;
		for (i = 0; i < 4; i++, pinfo += 16)
		{
			boot = pinfo[0];
			ptype = pinfo[4];
			start = SDL_SwapLE32(*(long*)(pinfo+8));
			sectors = SDL_SwapLE32(*(long*)(pinfo+12));
			total += sectors;
			LOG_TRACE(tracelevel, "- Partition %d: type=0x%02x, start=0x%08x, size=%.1f MB %s%s\n",
				  i, ptype, start, sectors/2048.0, boot ? "(boot)" : "", sectors ? "" : "(invalid)");
			if (ptype)
				parts++;
		}
		LOG_TRACE(tracelevel, "- Total size: %.1f MB in %d partitions\n", total/2048.0, parts);
	}
	else
	{
		/* Partition table contains hd size + 4 partition entries
		 * (composed of flag byte, 3 char ID, start offset
		 * and size), this is followed by bad sector list +
		 * count and the root sector checksum. Before this
		 * there's the boot code.
		 */
		char c, pid[4];
		int j, flags;
		bool extended;

		LOG_TRACE(tracelevel, "ATARI MBR:\n");
		pinfo = bootsector + 0x1C6;
		for (i = 0; i < 4; i++, pinfo += 12)
		{
			flags = pinfo[0];
			for (j = 0; j < 3; j++)
			{
				c = pinfo[j+1];
				if (c < 32 || c >= 127)
					c = '.';
				pid[j] = c;
			}
			pid[3] = '\0';
			extended = strcmp("XGM", pid) == 0;
			start = HDC_ReadInt32(pinfo, 4);
			sectors = HDC_ReadInt32(pinfo, 8);
			LOG_TRACE(tracelevel,
				  "- Partition %d: ID=%s, start=0x%08x, size=%.1f MB, flags=0x%x %s%s\n",
				  i, pid, start, sectors/2048.0, flags,
				  (flags & 0x80) ? "(boot)": "",
				  extended ? "(extended)" : "");
			if (flags & 0x1)
				parts++;
		}
		total = HDC_ReadInt32(bootsector, 0x1C2);
		LOG_TRACE(tracelevel, "- Total size: %.1f MB in %d partitions\n", total/2048.0, parts);
	}

	if (fseeko(fp, offset, SEEK_SET) != 0)
		perror("HDC_PartitionCount");
	return parts;
}

/**
 * Check file size for sane values (non-zero, multiple of 512),
 * and return the size
 */
off_t HDC_CheckAndGetSize(const char *hdtype, const char *filename, unsigned long blockSize)
{
	off_t filesize;
	char shortname[48];

	File_ShrinkName(shortname, filename, sizeof(shortname) - 1);

	filesize = File_Length(filename);
	if (filesize < 0)
	{
		Log_AlertDlg(LOG_ERROR, "Unable to get size of %s HD image file\n'%s'!",
		             hdtype, shortname);
		if (sizeof(off_t) < 8)
		{
			Log_Printf(LOG_ERROR, "Note: This version of Hatari has been built"
			                      " _without_ support for large files,\n"
			                      "      so you can not use HD images > 2 GB.\n");
		}
		return -EFBIG;
	}
	if (filesize == 0)
	{
		Log_AlertDlg(LOG_ERROR, "Can not use %s HD image file\n'%s'\n"
		                        "since the file is empty.",
		             hdtype, shortname);
		return -EINVAL;
	}
	if ((filesize & (blockSize - 1)) != 0)
	{
		Log_AlertDlg(LOG_ERROR, "Can not use the %s HD image file\n"
		                        "'%s'\nsince its size is not a multiple"
		                        " of %ld.", hdtype, shortname, blockSize);
		return -EINVAL;
	}

	return filesize;
}

/**
 * Open a disk image file
 */
int HDC_InitDevice(const char *hdtype, SCSI_DEV *dev, char *filename, unsigned long blockSize)
{
	off_t filesize;
	FILE *fp;

	dev->enabled = false;
	Log_Printf(LOG_INFO, "Mounting %s HD image '%s'\n", hdtype, filename);

	/* Check size for sanity */
	filesize = HDC_CheckAndGetSize(hdtype, filename, blockSize);
	if (filesize < 0)
		return filesize;

	if (!(fp = fopen(filename, "rb+")))
	{
		if (!(fp = fopen(filename, "rb")))
		{
			Log_AlertDlg(LOG_ERROR, "Cannot open %s HD file for reading\n'%s'!\n",
				     hdtype, filename);
			return -ENOENT;
		}
		Log_AlertDlg(LOG_WARN, "%s HD file is read-only, no writes will go through\n'%s'.\n",
			     hdtype, filename);
	}
	else if (!File_Lock(fp))
	{
		Log_AlertDlg(LOG_ERROR, "Locking %s HD file for writing failed\n'%s'!\n",
			     hdtype, filename);
		fclose(fp);
		return -ENOLCK;
	}

	dev->blockSize = blockSize;
	dev->hdSize = filesize / dev->blockSize;
	dev->image_file = fp;
	dev->enabled = true;

	return 0;
}

/**
 * Open the disk image files, set partitions.
 */
bool HDC_Init(void)
{
	int i;

	/* ACSI */
	nAcsiPartitions = 0;
	bAcsiEmuOn = false;
	memset(&AcsiBus, 0, sizeof(AcsiBus));
	AcsiBus.typestr = "ACSI";
	AcsiBus.buffer_size = 512;
	AcsiBus.buffer = malloc(AcsiBus.buffer_size);
	if (!AcsiBus.buffer)
	{
		perror("HDC_Init");
		return false;
	}
	for (i = 0; i < MAX_ACSI_DEVS; i++)
	{
		if (!ConfigureParams.Acsi[i].bUseDevice)
			continue;
		if (HDC_InitDevice("ACSI", &AcsiBus.devs[i], ConfigureParams.Acsi[i].sDeviceFile, ConfigureParams.Acsi[i].nBlockSize) == 0)
		{
			nAcsiPartitions += HDC_PartitionCount(AcsiBus.devs[i].image_file, TRACE_SCSI_CMD, NULL);
			bAcsiEmuOn = true;
		}
		else
			ConfigureParams.Acsi[i].bUseDevice = false;
	}
	/* set total number of partitions */
	nNumDrives += nAcsiPartitions;
	return bAcsiEmuOn;
}


/*---------------------------------------------------------------------*/
/**
 * HDC_UnInit - close image file
 *
 */
void HDC_UnInit(void)
{
	int i;

	for (i = 0; bAcsiEmuOn && i < MAX_ACSI_DEVS; i++)
	{
		if (!AcsiBus.devs[i].enabled)
			continue;
		File_UnLock(AcsiBus.devs[i].image_file);
		fclose(AcsiBus.devs[i].image_file);
		AcsiBus.devs[i].image_file = NULL;
		AcsiBus.devs[i].enabled = false;
	}
	free(AcsiBus.buffer);
	AcsiBus.buffer = NULL;

	nNumDrives -= nAcsiPartitions;
	nAcsiPartitions = 0;
	bAcsiEmuOn = false;
}


/*---------------------------------------------------------------------*/
/**
 * Reset command status.
 */
void HDC_ResetCommandStatus(void)
{
	if (!Config_IsMachineFalcon())
		AcsiBus.status = 0;
}


/**
 * Process HDC command packets (SCSI/ACSI) bytes.
 * @return true if command has been executed.
 */
bool HDC_WriteCommandPacket(SCSI_CTRLR *ctr, Uint8 b)
{
	bool bDidCmd = false;
	SCSI_DEV *dev = &ctr->devs[ctr->target];

	/* Abort if the target device is not enabled */
	if (!dev->enabled)
	{
		ctr->status = HD_STATUS_ERROR;
		return false;
	}

	/* Extract ACSI/SCSI opcode */
	if (ctr->byteCount == 0)
	{
		ctr->opcode = b;
		ctr->bDmaError = false;
	}

	/* Successfully received one byte, and increase the byte-count */
	if (ctr->byteCount < (int)sizeof(ctr->command))
		ctr->command[ctr->byteCount] = b;
	++ctr->byteCount;

	/* have we received a complete 6-byte class 0 or 10-byte class 1 packet yet? */
	if ((ctr->opcode < 0x20 && ctr->byteCount == 6) ||
	    (ctr->opcode >= 0x20 && ctr->opcode < 0x60 && ctr->byteCount == 10) ||
	    (ctr->opcode == 0xa0 && ctr->byteCount == 12))
	{
		/* We currently only support LUN 0, however INQUIRY must
		 * always be handled, see SCSI standard */
		if (HDC_GetLUN(ctr) == 0 || ctr->opcode == HD_INQUIRY)
		{
			HDC_EmulateCommandPacket(ctr);
			bDidCmd = true;
		}
		else
		{
			Log_Printf(LOG_WARN, "HDC: Access to non-existing LUN."
				   " Command = 0x%02x\n", ctr->opcode);
			dev->nLastError = HD_REQSENS_INVLUN;
			/* REQUEST SENSE is still handled for invalid LUNs */
			if (ctr->opcode == HD_REQ_SENSE)
			{
				HDC_Cmd_RequestSense(ctr);
				bDidCmd = true;
			}
			else
			{
				ctr->status = HD_STATUS_ERROR;
			}
		}
	}
	else if (ctr->opcode >= 0x60)
	{
		/* Commands >= 0x60 are not supported right now */
		ctr->status = HD_STATUS_ERROR;
		dev->nLastError = HD_REQSENS_OPCODE;
		dev->bSetLastBlockAddr = false;
		if (ctr->byteCount == 10)
		{
			LOG_TRACE(TRACE_SCSI_CMD, "HDC: Unsupported command (%s).\n",
			          HDC_CmdInfoStr(ctr));
		}
	}
	else
	{
		ctr->status = HD_STATUS_OK;
	}

	return bDidCmd;
}

/*---------------------------------------------------------------------*/

static void Acsi_DmaTransfer(void)
{
	Uint32 nDmaAddr = FDC_GetDMAAddress();
	Uint16 nDmaMode = FDC_DMA_GetMode();

	/* Don't do anything if no DMA to ACSI bus or nothing to transfer */
	if ((nDmaMode & 0xc0) != 0x00 || AcsiBus.data_len == 0)
		return;

	if ((AcsiBus.dmawrite_to_fh && (nDmaMode & 0x100) == 0)
	    || (!AcsiBus.dmawrite_to_fh && (nDmaMode & 0x100) != 0))
	{
		Log_Printf(LOG_WARN, "DMA direction does not match SCSI command!\n");
		return;
	}

	if (AcsiBus.dmawrite_to_fh)
	{
		/* write - if allowed */
		if (STMemory_CheckAreaType(nDmaAddr, AcsiBus.data_len, ABFLAG_RAM | ABFLAG_ROM))
		{
#ifndef DISALLOW_HDC_WRITE
			int wlen = fwrite(&STRam[nDmaAddr], 1, AcsiBus.data_len, AcsiBus.dmawrite_to_fh);
			if (wlen != AcsiBus.data_len)
			{
				Log_Printf(LOG_ERROR, "Could not write all bytes to ACSI HD image.\n");
				AcsiBus.status = HD_STATUS_ERROR;
			}
#endif
		}
		else
		{
			Log_Printf(LOG_WARN, "HDC DMA write uses invalid RAM range 0x%x+%i\n",
				   nDmaAddr, AcsiBus.data_len);
			AcsiBus.bDmaError = true;
		}
		AcsiBus.dmawrite_to_fh = NULL;
	}
	else if (!STMemory_SafeCopy(nDmaAddr, AcsiBus.buffer, AcsiBus.data_len, "ACSI DMA"))
	{
		AcsiBus.bDmaError = true;
		AcsiBus.status = HD_STATUS_ERROR;
	}

	FDC_WriteDMAAddress(nDmaAddr + AcsiBus.data_len);
	AcsiBus.data_len = 0;

	FDC_SetDMAStatus(AcsiBus.bDmaError);	/* Mark DMA error */
	FDC_SetIRQ(FDC_IRQ_SOURCE_HDC);
}

static void Acsi_WriteCommandByte(int addr, Uint8 byte)
{
	/* Clear IRQ initially (will be set again if byte has been accepted) */
	FDC_ClearHdcIRQ();

	/* When the A1 pin is pushed to 0, we want to start a new command.
	 * We ignore the pin for the second byte in the packet since this
	 * seems to happen on real hardware too (some buggy driver relies
	 * on this behavior). */
	if ((addr & 2) == 0 && AcsiBus.byteCount != 1)
	{
		AcsiBus.byteCount = 0;
		AcsiBus.target = ((byte & 0xE0) >> 5);
		/* Only process the first byte if it is not
		 * an extended ICD command marker byte */
		if ((byte & 0x1F) != 0x1F)
		{
			HDC_WriteCommandPacket(&AcsiBus, byte & 0x1F);
		}
		else
		{
			AcsiBus.status = HD_STATUS_OK;
			AcsiBus.bDmaError = false;
		}
	}
	else
	{
		/* Process normal command byte */
		bool bDidCmd = HDC_WriteCommandPacket(&AcsiBus, byte);
		if (bDidCmd && AcsiBus.status == HD_STATUS_OK && AcsiBus.data_len)
		{
			Acsi_DmaTransfer();
		}
	}

	if (AcsiBus.devs[AcsiBus.target].enabled)
	{
		FDC_SetDMAStatus(AcsiBus.bDmaError);	/* Mark DMA error */
		FDC_SetIRQ(FDC_IRQ_SOURCE_HDC);
	}
}

/**
 * Called when command bytes have been written to $FFFF8606 and
 * the HDC (not the FDC) is selected.
 */
void HDC_WriteCommandByte(int addr, Uint8 byte)
{
	// fprintf(stderr, "HDC: Write cmd byte addr=%i, byte=%02x\n", addr, byte);

	if (Config_IsMachineFalcon())
		Ncr5380_WriteByte(addr, byte);
	else if (bAcsiEmuOn)
		Acsi_WriteCommandByte(addr, byte);
}

/**
 * Get command byte.
 */
short int HDC_ReadCommandByte(int addr)
{
	Uint16 ret;
	if (Config_IsMachineFalcon())
		ret = Ncr5380_ReadByte(addr);
	else
		ret = AcsiBus.status;		/* ACSI status */
	return ret;
}

/**
 * Called when DMA transfer has just been enabled for the hard disk in the
 * $FFFF8606 (DMA mode) register.
 */
void HDC_DmaTransfer(void)
{
	if (Config_IsMachineFalcon())
		Ncr5380_DmaTransfer_Falcon();
	else if (bAcsiEmuOn)
		Acsi_DmaTransfer();
}