amiflop.c

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/*
 *  linux/amiga/amiflop.c
 *
 *  Copyright (C) 1993  Greg Harp
 *  Portions of this driver are based on code contributed by Brad Pepers
 *  
 *  revised 28.5.95 by Joerg Dorchain
 *  - now no bugs(?) any more for both HD & DD
 *  - added support for 40 Track 5.25" drives, 80-track hopefully behaves
 *    like 3.5" dd (no way to test - are there any 5.25" drives out there
 *    that work on an A4000?)
 *  - wrote formatting routine (maybe dirty, but works)
 *
 *  june/july 1995 added ms-dos support by Joerg Dorchain
 *  (portions based on messydos.device and various contributors)
 *  - currently only 9 and 18 sector disks
 *
 *  - fixed a bug with the internal trackbuffer when using multiple 
 *    disks the same time
 *  - made formatting a bit safer
 *  - added command line and machine based default for "silent" df0
 *
 *  december 1995 adapted for 1.2.13pl4 by Joerg Dorchain
 *  - works but I think it's inefficient. (look in redo_fd_request)
 *    But the changes were very efficient. (only three and a half lines)
 *
 *  january 1996 added special ioctl for tracking down read/write problems
 *  - usage ioctl(d, RAW_TRACK, ptr); the raw track buffer (MFM-encoded data
 *    is copied to area. (area should be large enough since no checking is
 *    done - 30K is currently sufficient). return the actual size of the
 *    trackbuffer
 *  - replaced udelays() by a timer (CIAA timer B) for the waits 
 *    needed for the disk mechanic.
 *
 *  february 1996 fixed error recovery and multiple disk access
 *  - both got broken the first time I tampered with the driver :-(
 *  - still not safe, but better than before
 *
 *  revised Marts 3rd, 1996 by Jes Sorensen for use in the 1.3.28 kernel.
 *  - Minor changes to accept the kdev_t.
 *  - Replaced some more udelays with ms_delays. Udelay is just a loop,
 *    and so the delay will be different depending on the given
 *    processor :-(
 *  - The driver could use a major cleanup because of the new
 *    major/minor handling that came with kdev_t. It seems to work for
 *    the time being, but I can't guarantee that it will stay like
 *    that when we start using 16 (24?) bit minors.
 *
 * restructured jan 1997 by Joerg Dorchain
 * - Fixed Bug accessing multiple disks
 * - some code cleanup
 * - added trackbuffer for each drive to speed things up
 * - fixed some race conditions (who finds the next may send it to me ;-)
 */

#include <linux/module.h>
#include <linux/slab.h>

#include <linux/fd.h>
#include <linux/hdreg.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/amifdreg.h>
#include <linux/amifd.h>
#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>

#include <asm/setup.h>
#include <asm/uaccess.h>
#include <asm/amigahw.h>
#include <asm/amigaints.h>
#include <asm/irq.h>

#undef DEBUG /* print _LOTS_ of infos */

#define RAW_IOCTL
#ifdef RAW_IOCTL
#define IOCTL_RAW_TRACK 0x5254524B  /* 'RTRK' */
#endif

/*
 *  Defines
 */

/*
 *  Error codes
 */
#define FD_OK       0   /* operation succeeded */
#define FD_ERROR    -1  /* general error (seek, read, write, etc) */
#define FD_NOUNIT   1   /* unit does not exist */
#define FD_UNITBUSY 2   /* unit already active */
#define FD_NOTACTIVE    3   /* unit is not active */
#define FD_NOTREADY 4   /* unit is not ready (motor not on/no disk) */

#define MFM_NOSYNC  1
#define MFM_HEADER  2
#define MFM_DATA    3
#define MFM_TRACK   4

/*
 *  Floppy ID values
 */
#define FD_NODRIVE  0x00000000  /* response when no unit is present */
#define FD_DD_3     0xffffffff  /* double-density 3.5" (880K) drive */
#define FD_HD_3     0x55555555  /* high-density 3.5" (1760K) drive */
#define FD_DD_5     0xaaaaaaaa  /* double-density 5.25" (440K) drive */

static DEFINE_MUTEX(amiflop_mutex);
static unsigned long int fd_def_df0 = FD_DD_3;     /* default for df0 if it doesn't identify */

module_param(fd_def_df0, ulong, 0);
MODULE_LICENSE("GPL");

/*
 *  Macros
 */
#define MOTOR_ON    (ciab.prb &= ~DSKMOTOR)
#define MOTOR_OFF   (ciab.prb |= DSKMOTOR)
#define SELECT(mask)    (ciab.prb &= ~mask)
#define DESELECT(mask)  (ciab.prb |= mask)
#define SELMASK(drive)  (1 << (3 + (drive & 3)))

static struct fd_drive_type drive_types[] = {
/*  code    name       tr he   rdsz   wrsz sm pc1 pc2 sd  st st*/
/*  warning: times are now in milliseconds (ms)                    */
{ FD_DD_3,  "DD 3.5",  80, 2, 14716, 13630, 1, 80,161, 3, 18, 1},
{ FD_HD_3,  "HD 3.5",  80, 2, 28344, 27258, 2, 80,161, 3, 18, 1},
{ FD_DD_5,  "DD 5.25", 40, 2, 14716, 13630, 1, 40, 81, 6, 30, 2},
{ FD_NODRIVE, "No Drive", 0, 0,     0,     0, 0,  0,  0,  0,  0, 0}
};
static int num_dr_types = ARRAY_SIZE(drive_types);

static int amiga_read(int), dos_read(int);
static void amiga_write(int), dos_write(int);
static struct fd_data_type data_types[] = {
    { "Amiga", 11 , amiga_read, amiga_write},
    { "MS-Dos", 9, dos_read, dos_write}
};

/* current info on each unit */
static struct amiga_floppy_struct unit[FD_MAX_UNITS];

static struct timer_list flush_track_timer[FD_MAX_UNITS];
static struct timer_list post_write_timer;
static struct timer_list motor_on_timer;
static struct timer_list motor_off_timer[FD_MAX_UNITS];
static int on_attempts;

/* Synchronization of FDC access */
/* request loop (trackbuffer) */
static volatile int fdc_busy = -1;
static volatile int fdc_nested;
static DECLARE_WAIT_QUEUE_HEAD(fdc_wait);
 
static DECLARE_COMPLETION(motor_on_completion);

static volatile int selected = -1;  /* currently selected drive */

static int writepending;
static int writefromint;
static char *raw_buf;
static int fdc_queue;

static DEFINE_SPINLOCK(amiflop_lock);

#define RAW_BUF_SIZE 30000  /* size of raw disk data */

/*
 * These are global variables, as that's the easiest way to give
 * information to interrupts. They are the data used for the current
 * request.
 */
static volatile char block_flag;
static DECLARE_WAIT_QUEUE_HEAD(wait_fd_block);

/* MS-Dos MFM Coding tables (should go quick and easy) */
static unsigned char mfmencode[16]={
    0x2a, 0x29, 0x24, 0x25, 0x12, 0x11, 0x14, 0x15,
    0x4a, 0x49, 0x44, 0x45, 0x52, 0x51, 0x54, 0x55
};
static unsigned char mfmdecode[128];

/* floppy internal millisecond timer stuff */
static DECLARE_COMPLETION(ms_wait_completion);
#define MS_TICKS ((amiga_eclock+50)/1000)

/*
 * Note that MAX_ERRORS=X doesn't imply that we retry every bad read
 * max X times - some types of errors increase the errorcount by 2 or
 * even 3, so we might actually retry only X/2 times before giving up.
 */
#define MAX_ERRORS 12

#define custom amiga_custom

/* Prevent "aliased" accesses. */
static int fd_ref[4] = { 0,0,0,0 };
static int fd_device[4] = { 0, 0, 0, 0 };

/*
 * Here come the actual hardware access and helper functions.
 * They are not reentrant and single threaded because all drives
 * share the same hardware and the same trackbuffer.
 */

/* Milliseconds timer */

static irqreturn_t ms_isr(int irq, void *dummy)
{
    complete(&ms_wait_completion);
    return IRQ_HANDLED;
}

/* all waits are queued up 
   A more generic routine would do a schedule a la timer.device */
static void ms_delay(int ms)
{
    int ticks;
    static DEFINE_MUTEX(mutex);

    if (ms > 0) {
        mutex_lock(&mutex);
        ticks = MS_TICKS*ms-1;
        ciaa.tblo=ticks%256;
        ciaa.tbhi=ticks/256;
        ciaa.crb=0x19; /*count eclock, force load, one-shoot, start */
        wait_for_completion(&ms_wait_completion);
        mutex_unlock(&mutex);
    }
}

/* Hardware semaphore */

/* returns true when we would get the semaphore */
static inline int try_fdc(int drive)
{
    drive &= 3;
    return ((fdc_busy < 0) || (fdc_busy == drive));
}

static void get_fdc(int drive)
{
    unsigned long flags;

    drive &= 3;
#ifdef DEBUG
    printk("get_fdc: drive %d  fdc_busy %d  fdc_nested %d\n",drive,fdc_busy,fdc_nested);
#endif
    local_irq_save(flags);
    wait_event(fdc_wait, try_fdc(drive));
    fdc_busy = drive;
    fdc_nested++;
    local_irq_restore(flags);
}

static inline void rel_fdc(void)
{
#ifdef DEBUG
    if (fdc_nested == 0)
        printk("fd: unmatched rel_fdc\n");
    printk("rel_fdc: fdc_busy %d fdc_nested %d\n",fdc_busy,fdc_nested);
#endif
    fdc_nested--;
    if (fdc_nested == 0) {
        fdc_busy = -1;
        wake_up(&fdc_wait);
    }
}

static void fd_select (int drive)
{
    unsigned char prb = ~0;

    drive&=3;
#ifdef DEBUG
    printk("selecting %d\n",drive);
#endif
    if (drive == selected)
        return;
    get_fdc(drive);
    selected = drive;

    if (unit[drive].track % 2 != 0)
        prb &= ~DSKSIDE;
    if (unit[drive].motor == 1)
        prb &= ~DSKMOTOR;
    ciab.prb |= (SELMASK(0)|SELMASK(1)|SELMASK(2)|SELMASK(3));
    ciab.prb = prb;
    prb &= ~SELMASK(drive);
    ciab.prb = prb;
    rel_fdc();
}

static void fd_deselect (int drive)
{
    unsigned char prb;
    unsigned long flags;

    drive&=3;
#ifdef DEBUG
    printk("deselecting %d\n",drive);
#endif
    if (drive != selected) {
        printk(KERN_WARNING "Deselecting drive %d while %d was selected!\n",drive,selected);
        return;
    }

    get_fdc(drive);
    local_irq_save(flags);

    selected = -1;

    prb = ciab.prb;
    prb |= (SELMASK(0)|SELMASK(1)|SELMASK(2)|SELMASK(3));
    ciab.prb = prb;

    local_irq_restore (flags);
    rel_fdc();

}

static void motor_on_callback(unsigned long nr)
{
    if (!(ciaa.pra & DSKRDY) || --on_attempts == 0) {
        complete_all(&motor_on_completion);
    } else {
        motor_on_timer.expires = jiffies + HZ/10;
        add_timer(&motor_on_timer);
    }
}

static int fd_motor_on(int nr)
{
    nr &= 3;

    del_timer(motor_off_timer + nr);

    if (!unit[nr].motor) {
        unit[nr].motor = 1;
        fd_select(nr);

        INIT_COMPLETION(motor_on_completion);
        motor_on_timer.data = nr;
        mod_timer(&motor_on_timer, jiffies + HZ/2);

        on_attempts = 10;
        wait_for_completion(&motor_on_completion);
        fd_deselect(nr);
    }

    if (on_attempts == 0) {
        on_attempts = -1;
#if 0
        printk (KERN_ERR "motor_on failed, turning motor off\n");
        fd_motor_off (nr);
        return 0;
#else
        printk (KERN_WARNING "DSKRDY not set after 1.5 seconds - assuming drive is spinning notwithstanding\n");
#endif
    }

    return 1;
}

static void fd_motor_off(unsigned long drive)
{
    long calledfromint;
#ifdef MODULE
    long decusecount;

    decusecount = drive & 0x40000000;
#endif
    calledfromint = drive & 0x80000000;
    drive&=3;
    if (calledfromint && !try_fdc(drive)) {
        /* We would be blocked in an interrupt, so try again later */
        motor_off_timer[drive].expires = jiffies + 1;
        add_timer(motor_off_timer + drive);
        return;
    }
    unit[drive].motor = 0;
    fd_select(drive);
    udelay (1);
    fd_deselect(drive);
}

static void floppy_off (unsigned int nr)
{
    int drive;

    drive = nr & 3;
    /* called this way it is always from interrupt */
    motor_off_timer[drive].data = nr | 0x80000000;
    mod_timer(motor_off_timer + drive, jiffies + 3*HZ);
}

static int fd_calibrate(int drive)
{
    unsigned char prb;
    int n;

    drive &= 3;
    get_fdc(drive);
    if (!fd_motor_on (drive))
        return 0;
    fd_select (drive);
    prb = ciab.prb;
    prb |= DSKSIDE;
    prb &= ~DSKDIREC;
    ciab.prb = prb;
    for (n = unit[drive].type->tracks/2; n != 0; --n) {
        if (ciaa.pra & DSKTRACK0)
            break;
        prb &= ~DSKSTEP;
        ciab.prb = prb;
        prb |= DSKSTEP;
        udelay (2);
        ciab.prb = prb;
        ms_delay(unit[drive].type->step_delay);
    }
    ms_delay (unit[drive].type->settle_time);
    prb |= DSKDIREC;
    n = unit[drive].type->tracks + 20;
    for (;;) {
        prb &= ~DSKSTEP;
        ciab.prb = prb;
        prb |= DSKSTEP;
        udelay (2);
        ciab.prb = prb;
        ms_delay(unit[drive].type->step_delay + 1);
        if ((ciaa.pra & DSKTRACK0) == 0)
            break;
        if (--n == 0) {
            printk (KERN_ERR "fd%d: calibrate failed, turning motor off\n", drive);
            fd_motor_off (drive);
            unit[drive].track = -1;
            rel_fdc();
            return 0;
        }
    }
    unit[drive].track = 0;
    ms_delay(unit[drive].type->settle_time);

    rel_fdc();
    fd_deselect(drive);
    return 1;
}

static int fd_seek(int drive, int track)
{
    unsigned char prb;
    int cnt;

#ifdef DEBUG
    printk("seeking drive %d to track %d\n",drive,track);
#endif
    drive &= 3;
    get_fdc(drive);
    if (unit[drive].track == track) {
        rel_fdc();
        return 1;
    }
    if (!fd_motor_on(drive)) {
        rel_fdc();
        return 0;
    }
    if (unit[drive].track < 0 && !fd_calibrate(drive)) {
        rel_fdc();
        return 0;
    }

    fd_select (drive);
    cnt = unit[drive].track/2 - track/2;
    prb = ciab.prb;
    prb |= DSKSIDE | DSKDIREC;
    if (track % 2 != 0)
        prb &= ~DSKSIDE;
    if (cnt < 0) {
        cnt = - cnt;
        prb &= ~DSKDIREC;
    }
    ciab.prb = prb;
    if (track % 2 != unit[drive].track % 2)
        ms_delay (unit[drive].type->side_time);
    unit[drive].track = track;
    if (cnt == 0) {
        rel_fdc();
        fd_deselect(drive);
        return 1;
    }
    do {
        prb &= ~DSKSTEP;
        ciab.prb = prb;
        prb |= DSKSTEP;
        udelay (1);
        ciab.prb = prb;
        ms_delay (unit[drive].type->step_delay);
    } while (--cnt != 0);
    ms_delay (unit[drive].type->settle_time);

    rel_fdc();
    fd_deselect(drive);
    return 1;
}

static unsigned long fd_get_drive_id(int drive)
{
    int i;
    ulong id = 0;

    drive&=3;
    get_fdc(drive);
    /* set up for ID */
    MOTOR_ON;
    udelay(2);
    SELECT(SELMASK(drive));
    udelay(2);
    DESELECT(SELMASK(drive));
    udelay(2);
    MOTOR_OFF;
    udelay(2);
    SELECT(SELMASK(drive));
    udelay(2);
    DESELECT(SELMASK(drive));
    udelay(2);

    /* loop and read disk ID */
    for (i=0; i<32; i++) {
        SELECT(SELMASK(drive));
        udelay(2);

        /* read and store value of DSKRDY */
        id <<= 1;
        id |= (ciaa.pra & DSKRDY) ? 0 : 1;  /* cia regs are low-active! */

        DESELECT(SELMASK(drive));
    }

    rel_fdc();

        /*
         * RB: At least A500/A2000's df0: don't identify themselves.
         * As every (real) Amiga has at least a 3.5" DD drive as df0:
         * we default to that if df0: doesn't identify as a certain
         * type.
         */
        if(drive == 0 && id == FD_NODRIVE)
    {
                id = fd_def_df0;
                printk(KERN_NOTICE "fd: drive 0 didn't identify, setting default %08lx\n", (ulong)fd_def_df0);
    }
    /* return the ID value */
    return (id);
}

static irqreturn_t fd_block_done(int irq, void *dummy)
{
    if (block_flag)
        custom.dsklen = 0x4000;

    if (block_flag == 2) { /* writing */
        writepending = 2;
        post_write_timer.expires = jiffies + 1; /* at least 2 ms */
        post_write_timer.data = selected;
        add_timer(&post_write_timer);
    }
    else {                /* reading */
        block_flag = 0;
        wake_up (&wait_fd_block);
    }
    return IRQ_HANDLED;
}

static void raw_read(int drive)
{
    drive&=3;
    get_fdc(drive);
    wait_event(wait_fd_block, !block_flag);
    fd_select(drive);
    /* setup adkcon bits correctly */
    custom.adkcon = ADK_MSBSYNC;
    custom.adkcon = ADK_SETCLR|ADK_WORDSYNC|ADK_FAST;

    custom.dsksync = MFM_SYNC;

    custom.dsklen = 0;
    custom.dskptr = (u_char *)ZTWO_PADDR((u_char *)raw_buf);
    custom.dsklen = unit[drive].type->read_size/sizeof(short) | DSKLEN_DMAEN;
    custom.dsklen = unit[drive].type->read_size/sizeof(short) | DSKLEN_DMAEN;

    block_flag = 1;

    wait_event(wait_fd_block, !block_flag);

    custom.dsklen = 0;
    fd_deselect(drive);
    rel_fdc();
}

static int raw_write(int drive)
{
    ushort adk;

    drive&=3;
    get_fdc(drive); /* corresponds to rel_fdc() in post_write() */
    if ((ciaa.pra & DSKPROT) == 0) {
        rel_fdc();
        return 0;
    }
    wait_event(wait_fd_block, !block_flag);
    fd_select(drive);
    /* clear adkcon bits */
    custom.adkcon = ADK_PRECOMP1|ADK_PRECOMP0|ADK_WORDSYNC|ADK_MSBSYNC;
    /* set appropriate adkcon bits */
    adk = ADK_SETCLR|ADK_FAST;
    if ((ulong)unit[drive].track >= unit[drive].type->precomp2)
        adk |= ADK_PRECOMP1;
    else if ((ulong)unit[drive].track >= unit[drive].type->precomp1)
        adk |= ADK_PRECOMP0;
    custom.adkcon = adk;

    custom.dsklen = DSKLEN_WRITE;
    custom.dskptr = (u_char *)ZTWO_PADDR((u_char *)raw_buf);
    custom.dsklen = unit[drive].type->write_size/sizeof(short) | DSKLEN_DMAEN|DSKLEN_WRITE;
    custom.dsklen = unit[drive].type->write_size/sizeof(short) | DSKLEN_DMAEN|DSKLEN_WRITE;

    block_flag = 2;
    return 1;
}

/*
 * to be called at least 2ms after the write has finished but before any
 * other access to the hardware.
 */
static void post_write (unsigned long drive)
{
#ifdef DEBUG
    printk("post_write for drive %ld\n",drive);
#endif
    drive &= 3;
    custom.dsklen = 0;
    block_flag = 0;
    writepending = 0;
    writefromint = 0;
    unit[drive].dirty = 0;
    wake_up(&wait_fd_block);
    fd_deselect(drive);
    rel_fdc(); /* corresponds to get_fdc() in raw_write */
}


/*
 * The following functions are to convert the block contents into raw data
 * written to disk and vice versa.
 * (Add other formats here ;-))
 */

static unsigned long scan_sync(unsigned long raw, unsigned long end)
{
    ushort *ptr = (ushort *)raw, *endp = (ushort *)end;

    while (ptr < endp && *ptr++ != 0x4489)
        ;
    if (ptr < endp) {
        while (*ptr == 0x4489 && ptr < endp)
            ptr++;
        return (ulong)ptr;
    }
    return 0;
}

static inline unsigned long checksum(unsigned long *addr, int len)
{
    unsigned long csum = 0;

    len /= sizeof(*addr);
    while (len-- > 0)
        csum ^= *addr++;
    csum = ((csum>>1) & 0x55555555)  ^  (csum & 0x55555555);

    return csum;
}

static unsigned long decode (unsigned long *data, unsigned long *raw,
                 int len)
{
    ulong *odd, *even;

    /* convert length from bytes to longwords */
    len >>= 2;
    odd = raw;
    even = odd + len;

    /* prepare return pointer */
    raw += len * 2;

    do {
        *data++ = ((*odd++ & 0x55555555) << 1) | (*even++ & 0x55555555);
    } while (--len != 0);

    return (ulong)raw;
}

struct header {
    unsigned char magic;
    unsigned char track;
    unsigned char sect;
    unsigned char ord;
    unsigned char labels[16];
    unsigned long hdrchk;
    unsigned long datachk;
};

static int amiga_read(int drive)
{
    unsigned long raw;
    unsigned long end;
    int scnt;
    unsigned long csum;
    struct header hdr;

    drive&=3;
    raw = (long) raw_buf;
    end = raw + unit[drive].type->read_size;

    for (scnt = 0;scnt < unit[drive].dtype->sects * unit[drive].type->sect_mult; scnt++) {
        if (!(raw = scan_sync(raw, end))) {
            printk (KERN_INFO "can't find sync for sector %d\n", scnt);
            return MFM_NOSYNC;
        }

        raw = decode ((ulong *)&hdr.magic, (ulong *)raw, 4);
        raw = decode ((ulong *)&hdr.labels, (ulong *)raw, 16);
        raw = decode ((ulong *)&hdr.hdrchk, (ulong *)raw, 4);
        raw = decode ((ulong *)&hdr.datachk, (ulong *)raw, 4);
        csum = checksum((ulong *)&hdr,
                (char *)&hdr.hdrchk-(char *)&hdr);

#ifdef DEBUG
        printk ("(%x,%d,%d,%d) (%lx,%lx,%lx,%lx) %lx %lx\n",
            hdr.magic, hdr.track, hdr.sect, hdr.ord,
            *(ulong *)&hdr.labels[0], *(ulong *)&hdr.labels[4],
            *(ulong *)&hdr.labels[8], *(ulong *)&hdr.labels[12],
            hdr.hdrchk, hdr.datachk);
#endif

        if (hdr.hdrchk != csum) {
            printk(KERN_INFO "MFM_HEADER: %08lx,%08lx\n", hdr.hdrchk, csum);
            return MFM_HEADER;
        }

        /* verify track */
        if (hdr.track != unit[drive].track) {
            printk(KERN_INFO "MFM_TRACK: %d, %d\n", hdr.track, unit[drive].track);
            return MFM_TRACK;
        }

        raw = decode ((ulong *)(unit[drive].trackbuf + hdr.sect*512),
                  (ulong *)raw, 512);
        csum = checksum((ulong *)(unit[drive].trackbuf + hdr.sect*512), 512);

        if (hdr.datachk != csum) {
            printk(KERN_INFO "MFM_DATA: (%x:%d:%d:%d) sc=%d %lx, %lx\n",
                   hdr.magic, hdr.track, hdr.sect, hdr.ord, scnt,
                   hdr.datachk, csum);
            printk (KERN_INFO "data=(%lx,%lx,%lx,%lx)\n",
                ((ulong *)(unit[drive].trackbuf+hdr.sect*512))[0],
                ((ulong *)(unit[drive].trackbuf+hdr.sect*512))[1],
                ((ulong *)(unit[drive].trackbuf+hdr.sect*512))[2],
                ((ulong *)(unit[drive].trackbuf+hdr.sect*512))[3]);
            return MFM_DATA;
        }
    }

    return 0;
}

static void encode(unsigned long data, unsigned long *dest)
{
    unsigned long data2;

    data &= 0x55555555;
    data2 = data ^ 0x55555555;
    data |= ((data2 >> 1) | 0x80000000) & (data2 << 1);

    if (*(dest - 1) & 0x00000001)
        data &= 0x7FFFFFFF;

    *dest = data;
}

static void encode_block(unsigned long *dest, unsigned long *src, int len)
{
    int cnt, to_cnt = 0;
    unsigned long data;

    /* odd bits */
    for (cnt = 0; cnt < len / 4; cnt++) {
        data = src[cnt] >> 1;
        encode(data, dest + to_cnt++);
    }

    /* even bits */
    for (cnt = 0; cnt < len / 4; cnt++) {
        data = src[cnt];
        encode(data, dest + to_cnt++);
    }
}

static unsigned long *putsec(int disk, unsigned long *raw, int cnt)
{
    struct header hdr;
    int i;

    disk&=3;
    *raw = (raw[-1]&1) ? 0x2AAAAAAA : 0xAAAAAAAA;
    raw++;
    *raw++ = 0x44894489;

    hdr.magic = 0xFF;
    hdr.track = unit[disk].track;
    hdr.sect = cnt;
    hdr.ord = unit[disk].dtype->sects * unit[disk].type->sect_mult - cnt;
    for (i = 0; i < 16; i++)
        hdr.labels[i] = 0;
    hdr.hdrchk = checksum((ulong *)&hdr,
                  (char *)&hdr.hdrchk-(char *)&hdr);
    hdr.datachk = checksum((ulong *)(unit[disk].trackbuf+cnt*512), 512);

    encode_block(raw, (ulong *)&hdr.magic, 4);
    raw += 2;
    encode_block(raw, (ulong *)&hdr.labels, 16);
    raw += 8;
    encode_block(raw, (ulong *)&hdr.hdrchk, 4);
    raw += 2;
    encode_block(raw, (ulong *)&hdr.datachk, 4);
    raw += 2;
    encode_block(raw, (ulong *)(unit[disk].trackbuf+cnt*512), 512);
    raw += 256;

    return raw;
}

static void amiga_write(int disk)
{
    unsigned int cnt;
    unsigned long *ptr = (unsigned long *)raw_buf;

    disk&=3;
    /* gap space */
    for (cnt = 0; cnt < 415 * unit[disk].type->sect_mult; cnt++)
        *ptr++ = 0xaaaaaaaa;

    /* sectors */
    for (cnt = 0; cnt < unit[disk].dtype->sects * unit[disk].type->sect_mult; cnt++)
        ptr = putsec (disk, ptr, cnt);
    *(ushort *)ptr = (ptr[-1]&1) ? 0x2AA8 : 0xAAA8;
}


struct dos_header {
    unsigned char track,   /* 0-80 */
        side,    /* 0-1 */
        sec,     /* 0-...*/
        len_desc;/* 2 */
    unsigned short crc;     /* on 68000 we got an alignment problem, 
                   but this compiler solves it  by adding silently 
                   adding a pad byte so data won't fit
                   and this took about 3h to discover.... */
    unsigned char gap1[22];     /* for longword-alignedness (0x4e) */
};

/* crc routines are borrowed from the messydos-handler  */

/* excerpt from the messydos-device           
; The CRC is computed not only over the actual data, but including
; the SYNC mark (3 * $a1) and the 'ID/DATA - Address Mark' ($fe/$fb).
; As we don't read or encode these fields into our buffers, we have to
; preload the registers containing the CRC with the values they would have
; after stepping over these fields.
;
; How CRCs "really" work:
;
; First, you should regard a bitstring as a series of coefficients of
; polynomials. We calculate with these polynomials in modulo-2
; arithmetic, in which both add and subtract are done the same as
; exclusive-or. Now, we modify our data (a very long polynomial) in
; such a way that it becomes divisible by the CCITT-standard 16-bit
;        16   12   5
; polynomial:   x  + x  + x + 1, represented by $11021. The easiest
; way to do this would be to multiply (using proper arithmetic) our
; datablock with $11021. So we have:
;   data * $11021        =
;   data * ($10000 + $1021)      =
;   data * $10000 + data * $1021
; The left part of this is simple: Just add two 0 bytes. But then
; the right part (data $1021) remains difficult and even could have
; a carry into the left part. The solution is to use a modified
; multiplication, which has a result that is not correct, but with
; a difference of any multiple of $11021. We then only need to keep
; the 16 least significant bits of the result.
;
; The following algorithm does this for us:
;
;   unsigned char *data, c, crclo, crchi;
;   while (not done) {
;   c = *data++ + crchi;
;   crchi = (@ c) >> 8 + crclo;
;   crclo = @ c;
;   }
;
; Remember, + is done with EOR, the @ operator is in two tables (high
; and low byte separately), which is calculated as
;
;      $1021 * (c & $F0)
;  xor $1021 * (c & $0F)
;  xor $1021 * (c >> 4)         (* is regular multiplication)
;
;
; Anyway, the end result is the same as the remainder of the division of
; the data by $11021. I am afraid I need to study theory a bit more...


my only works was to code this from manx to C....

*/

static ushort dos_crc(void * data_a3, int data_d0, int data_d1, int data_d3)
{
    static unsigned char CRCTable1[] = {
        0x00,0x10,0x20,0x30,0x40,0x50,0x60,0x70,0x81,0x91,0xa1,0xb1,0xc1,0xd1,0xe1,0xf1,
        0x12,0x02,0x32,0x22,0x52,0x42,0x72,0x62,0x93,0x83,0xb3,0xa3,0xd3,0xc3,0xf3,0xe3,
        0x24,0x34,0x04,0x14,0x64,0x74,0x44,0x54,0xa5,0xb5,0x85,0x95,0xe5,0xf5,0xc5,0xd5,
        0x36,0x26,0x16,0x06,0x76,0x66,0x56,0x46,0xb7,0xa7,0x97,0x87,0xf7,0xe7,0xd7,0xc7,
        0x48,0x58,0x68,0x78,0x08,0x18,0x28,0x38,0xc9,0xd9,0xe9,0xf9,0x89,0x99,0xa9,0xb9,
        0x5a,0x4a,0x7a,0x6a,0x1a,0x0a,0x3a,0x2a,0xdb,0xcb,0xfb,0xeb,0x9b,0x8b,0xbb,0xab,
        0x6c,0x7c,0x4c,0x5c,0x2c,0x3c,0x0c,0x1c,0xed,0xfd,0xcd,0xdd,0xad,0xbd,0x8d,0x9d,
        0x7e,0x6e,0x5e,0x4e,0x3e,0x2e,0x1e,0x0e,0xff,0xef,0xdf,0xcf,0xbf,0xaf,0x9f,0x8f,
        0x91,0x81,0xb1,0xa1,0xd1,0xc1,0xf1,0xe1,0x10,0x00,0x30,0x20,0x50,0x40,0x70,0x60,
        0x83,0x93,0xa3,0xb3,0xc3,0xd3,0xe3,0xf3,0x02,0x12,0x22,0x32,0x42,0x52,0x62,0x72,
        0xb5,0xa5,0x95,0x85,0xf5,0xe5,0xd5,0xc5,0x34,0x24,0x14,0x04,0x74,0x64,0x54,0x44,
        0xa7,0xb7,0x87,0x97,0xe7,0xf7,0xc7,0xd7,0x26,0x36,0x06,0x16,0x66,0x76,0x46,0x56,
        0xd9,0xc9,0xf9,0xe9,0x99,0x89,0xb9,0xa9,0x58,0x48,0x78,0x68,0x18,0x08,0x38,0x28,
        0xcb,0xdb,0xeb,0xfb,0x8b,0x9b,0xab,0xbb,0x4a,0x5a,0x6a,0x7a,0x0a,0x1a,0x2a,0x3a,
        0xfd,0xed,0xdd,0xcd,0xbd,0xad,0x9d,0x8d,0x7c,0x6c,0x5c,0x4c,0x3c,0x2c,0x1c,0x0c,
        0xef,0xff,0xcf,0xdf,0xaf,0xbf,0x8f,0x9f,0x6e,0x7e,0x4e,0x5e,0x2e,0x3e,0x0e,0x1e
    };

    static unsigned char CRCTable2[] = {
        0x00,0x21,0x42,0x63,0x84,0xa5,0xc6,0xe7,0x08,0x29,0x4a,0x6b,0x8c,0xad,0xce,0xef,
        0x31,0x10,0x73,0x52,0xb5,0x94,0xf7,0xd6,0x39,0x18,0x7b,0x5a,0xbd,0x9c,0xff,0xde,
        0x62,0x43,0x20,0x01,0xe6,0xc7,0xa4,0x85,0x6a,0x4b,0x28,0x09,0xee,0xcf,0xac,0x8d,
        0x53,0x72,0x11,0x30,0xd7,0xf6,0x95,0xb4,0x5b,0x7a,0x19,0x38,0xdf,0xfe,0x9d,0xbc,
        0xc4,0xe5,0x86,0xa7,0x40,0x61,0x02,0x23,0xcc,0xed,0x8e,0xaf,0x48,0x69,0x0a,0x2b,
        0xf5,0xd4,0xb7,0x96,0x71,0x50,0x33,0x12,0xfd,0xdc,0xbf,0x9e,0x79,0x58,0x3b,0x1a,
        0xa6,0x87,0xe4,0xc5,0x22,0x03,0x60,0x41,0xae,0x8f,0xec,0xcd,0x2a,0x0b,0x68,0x49,
        0x97,0xb6,0xd5,0xf4,0x13,0x32,0x51,0x70,0x9f,0xbe,0xdd,0xfc,0x1b,0x3a,0x59,0x78,
        0x88,0xa9,0xca,0xeb,0x0c,0x2d,0x4e,0x6f,0x80,0xa1,0xc2,0xe3,0x04,0x25,0x46,0x67,
        0xb9,0x98,0xfb,0xda,0x3d,0x1c,0x7f,0x5e,0xb1,0x90,0xf3,0xd2,0x35,0x14,0x77,0x56,
        0xea,0xcb,0xa8,0x89,0x6e,0x4f,0x2c,0x0d,0xe2,0xc3,0xa0,0x81,0x66,0x47,0x24,0x05,
        0xdb,0xfa,0x99,0xb8,0x5f,0x7e,0x1d,0x3c,0xd3,0xf2,0x91,0xb0,0x57,0x76,0x15,0x34,
        0x4c,0x6d,0x0e,0x2f,0xc8,0xe9,0x8a,0xab,0x44,0x65,0x06,0x27,0xc0,0xe1,0x82,0xa3,
        0x7d,0x5c,0x3f,0x1e,0xf9,0xd8,0xbb,0x9a,0x75,0x54,0x37,0x16,0xf1,0xd0,0xb3,0x92,
        0x2e,0x0f,0x6c,0x4d,0xaa,0x8b,0xe8,0xc9,0x26,0x07,0x64,0x45,0xa2,0x83,0xe0,0xc1,
        0x1f,0x3e,0x5d,0x7c,0x9b,0xba,0xd9,0xf8,0x17,0x36,0x55,0x74,0x93,0xb2,0xd1,0xf0
    };

/* look at the asm-code - what looks in C a bit strange is almost as good as handmade */
    register int i;
    register unsigned char *CRCT1, *CRCT2, *data, c, crch, crcl;

    CRCT1=CRCTable1;
    CRCT2=CRCTable2;
    data=data_a3;
    crcl=data_d1;
    crch=data_d0;
    for (i=data_d3; i>=0; i--) {
        c = (*data++) ^ crch;
        crch = CRCT1[c] ^ crcl;
        crcl = CRCT2[c];
    }
    return (crch<<8)|crcl;
}

static inline ushort dos_hdr_crc (struct dos_header *hdr)
{
    return dos_crc(&(hdr->track), 0xb2, 0x30, 3); /* precomputed magic */
}

static inline ushort dos_data_crc(unsigned char *data)
{
    return dos_crc(data, 0xe2, 0x95 ,511); /* precomputed magic */
}

static inline unsigned char dos_decode_byte(ushort word)
{
    register ushort w2;
    register unsigned char byte;
    register unsigned char *dec = mfmdecode;

    w2=word;
    w2>>=8;
    w2&=127;
    byte = dec[w2];
    byte <<= 4;
    w2 = word & 127;
    byte |= dec[w2];
    return byte;
}

static unsigned long dos_decode(unsigned char *data, unsigned short *raw, int len)
{
    int i;

    for (i = 0; i < len; i++)
        *data++=dos_decode_byte(*raw++);
    return ((ulong)raw);
}

#ifdef DEBUG
static void dbg(unsigned long ptr)
{
    printk("raw data @%08lx: %08lx, %08lx ,%08lx, %08lx\n", ptr,
           ((ulong *)ptr)[0], ((ulong *)ptr)[1],
           ((ulong *)ptr)[2], ((ulong *)ptr)[3]);
}
#endif

static int dos_read(int drive)
{
    unsigned long end;
    unsigned long raw;
    int scnt;
    unsigned short crc,data_crc[2];
    struct dos_header hdr;

    drive&=3;
    raw = (long) raw_buf;
    end = raw + unit[drive].type->read_size;

    for (scnt=0; scnt < unit[drive].dtype->sects * unit[drive].type->sect_mult; scnt++) {
        do { /* search for the right sync of each sec-hdr */
            if (!(raw = scan_sync (raw, end))) {
                printk(KERN_INFO "dos_read: no hdr sync on "
                       "track %d, unit %d for sector %d\n",
                       unit[drive].track,drive,scnt);
                return MFM_NOSYNC;
            }
#ifdef DEBUG
            dbg(raw);
#endif
        } while (*((ushort *)raw)!=0x5554); /* loop usually only once done */
        raw+=2; /* skip over headermark */
        raw = dos_decode((unsigned char *)&hdr,(ushort *) raw,8);
        crc = dos_hdr_crc(&hdr);

#ifdef DEBUG
        printk("(%3d,%d,%2d,%d) %x\n", hdr.track, hdr.side,
               hdr.sec, hdr.len_desc, hdr.crc);
#endif

        if (crc != hdr.crc) {
            printk(KERN_INFO "dos_read: MFM_HEADER %04x,%04x\n",
                   hdr.crc, crc);
            return MFM_HEADER;
        }
        if (hdr.track != unit[drive].track/unit[drive].type->heads) {
            printk(KERN_INFO "dos_read: MFM_TRACK %d, %d\n",
                   hdr.track,
                   unit[drive].track/unit[drive].type->heads);
            return MFM_TRACK;
        }

        if (hdr.side != unit[drive].track%unit[drive].type->heads) {
            printk(KERN_INFO "dos_read: MFM_SIDE %d, %d\n",
                   hdr.side,
                   unit[drive].track%unit[drive].type->heads);
            return MFM_TRACK;
        }

        if (hdr.len_desc != 2) {
            printk(KERN_INFO "dos_read: unknown sector len "
                   "descriptor %d\n", hdr.len_desc);
            return MFM_DATA;
        }
#ifdef DEBUG
        printk("hdr accepted\n");
#endif
        if (!(raw = scan_sync (raw, end))) {
            printk(KERN_INFO "dos_read: no data sync on track "
                   "%d, unit %d for sector%d, disk sector %d\n",
                   unit[drive].track, drive, scnt, hdr.sec);
            return MFM_NOSYNC;
        }
#ifdef DEBUG
        dbg(raw);
#endif

        if (*((ushort *)raw)!=0x5545) {
            printk(KERN_INFO "dos_read: no data mark after "
                   "sync (%d,%d,%d,%d) sc=%d\n",
                   hdr.track,hdr.side,hdr.sec,hdr.len_desc,scnt);
            return MFM_NOSYNC;
        }

        raw+=2;  /* skip data mark (included in checksum) */
        raw = dos_decode((unsigned char *)(unit[drive].trackbuf + (hdr.sec - 1) * 512), (ushort *) raw, 512);
        raw = dos_decode((unsigned char  *)data_crc,(ushort *) raw,4);
        crc = dos_data_crc(unit[drive].trackbuf + (hdr.sec - 1) * 512);

        if (crc != data_crc[0]) {
            printk(KERN_INFO "dos_read: MFM_DATA (%d,%d,%d,%d) "
                   "sc=%d, %x %x\n", hdr.track, hdr.side,
                   hdr.sec, hdr.len_desc, scnt,data_crc[0], crc);
            printk(KERN_INFO "data=(%lx,%lx,%lx,%lx,...)\n",
                   ((ulong *)(unit[drive].trackbuf+(hdr.sec-1)*512))[0],
                   ((ulong *)(unit[drive].trackbuf+(hdr.sec-1)*512))[1],
                   ((ulong *)(unit[drive].trackbuf+(hdr.sec-1)*512))[2],
                   ((ulong *)(unit[drive].trackbuf+(hdr.sec-1)*512))[3]);
            return MFM_DATA;
        }
    }
    return 0;
}

static inline ushort dos_encode_byte(unsigned char byte)
{
    register unsigned char *enc, b2, b1;
    register ushort word;

    enc=mfmencode;
    b1=byte;
    b2=b1>>4;
    b1&=15;
    word=enc[b2] <<8 | enc [b1];
    return (word|((word&(256|64)) ? 0: 128));
}

static void dos_encode_block(ushort *dest, unsigned char *src, int len)
{
    int i;

    for (i = 0; i < len; i++) {
        *dest=dos_encode_byte(*src++);
        *dest|=((dest[-1]&1)||(*dest&0x4000))? 0: 0x8000;
        dest++;
    }
}

static unsigned long *ms_putsec(int drive, unsigned long *raw, int cnt)
{
    static struct dos_header hdr={0,0,0,2,0,
      {78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78}};
    int i;
    static ushort crc[2]={0,0x4e4e};

    drive&=3;
/* id gap 1 */
/* the MFM word before is always 9254 */
    for(i=0;i<6;i++)
        *raw++=0xaaaaaaaa;
/* 3 sync + 1 headermark */
    *raw++=0x44894489;
    *raw++=0x44895554;

/* fill in the variable parts of the header */
    hdr.track=unit[drive].track/unit[drive].type->heads;
    hdr.side=unit[drive].track%unit[drive].type->heads;
    hdr.sec=cnt+1;
    hdr.crc=dos_hdr_crc(&hdr);

/* header (without "magic") and id gap 2*/
    dos_encode_block((ushort *)raw,(unsigned char *) &hdr.track,28);
    raw+=14;

/*id gap 3 */
    for(i=0;i<6;i++)
        *raw++=0xaaaaaaaa;

/* 3 syncs and 1 datamark */
    *raw++=0x44894489;
    *raw++=0x44895545;

/* data */
    dos_encode_block((ushort *)raw,
             (unsigned char *)unit[drive].trackbuf+cnt*512,512);
    raw+=256;

/*data crc + jd's special gap (long words :-/) */
    crc[0]=dos_data_crc(unit[drive].trackbuf+cnt*512);
    dos_encode_block((ushort *) raw,(unsigned char *)crc,4);
    raw+=2;

/* data gap */
    for(i=0;i<38;i++)
        *raw++=0x92549254;

    return raw; /* wrote 652 MFM words */
}

static void dos_write(int disk)
{
    int cnt;
    unsigned long raw = (unsigned long) raw_buf;
    unsigned long *ptr=(unsigned long *)raw;

    disk&=3;
/* really gap4 + indexgap , but we write it first and round it up */
    for (cnt=0;cnt<425;cnt++)
        *ptr++=0x92549254;

/* the following is just guessed */
    if (unit[disk].type->sect_mult==2)  /* check for HD-Disks */
        for(cnt=0;cnt<473;cnt++)
            *ptr++=0x92549254;

/* now the index marks...*/
    for (cnt=0;cnt<20;cnt++)
        *ptr++=0x92549254;
    for (cnt=0;cnt<6;cnt++)
        *ptr++=0xaaaaaaaa;
    *ptr++=0x52245224;
    *ptr++=0x52245552;
    for (cnt=0;cnt<20;cnt++)
        *ptr++=0x92549254;

/* sectors */
    for(cnt = 0; cnt < unit[disk].dtype->sects * unit[disk].type->sect_mult; cnt++)
        ptr=ms_putsec(disk,ptr,cnt);

    *(ushort *)ptr = 0xaaa8; /* MFM word before is always 0x9254 */
}

/*
 * Here comes the high level stuff (i.e. the filesystem interface)
 * and helper functions.
 * Normally this should be the only part that has to be adapted to
 * different kernel versions.
 */

/* FIXME: this assumes the drive is still spinning -
 * which is only true if we complete writing a track within three seconds
 */
static void flush_track_callback(unsigned long nr)
{
    nr&=3;
    writefromint = 1;
    if (!try_fdc(nr)) {
        /* we might block in an interrupt, so try again later */
        flush_track_timer[nr].expires = jiffies + 1;
        add_timer(flush_track_timer + nr);
        return;
    }
    get_fdc(nr);
    (*unit[nr].dtype->write_fkt)(nr);
    if (!raw_write(nr)) {
        printk (KERN_NOTICE "floppy disk write protected\n");
        writefromint = 0;
        writepending = 0;
    }
    rel_fdc();
}

static int non_int_flush_track (unsigned long nr)
{
    unsigned long flags;

    nr&=3;
    writefromint = 0;
    del_timer(&post_write_timer);
    get_fdc(nr);
    if (!fd_motor_on(nr)) {
        writepending = 0;
        rel_fdc();
        return 0;
    }
    local_irq_save(flags);
    if (writepending != 2) {
        local_irq_restore(flags);
        (*unit[nr].dtype->write_fkt)(nr);
        if (!raw_write(nr)) {
            printk (KERN_NOTICE "floppy disk write protected "
                "in write!\n");
            writepending = 0;
            return 0;
        }
        wait_event(wait_fd_block, block_flag != 2);
    }
    else {
        local_irq_restore(flags);
        ms_delay(2); /* 2 ms post_write delay */
        post_write(nr);
    }
    rel_fdc();
    return 1;
}

static int get_track(int drive, int track)
{
    int error, errcnt;

    drive&=3;
    if (unit[drive].track == track)
        return 0;
    get_fdc(drive);
    if (!fd_motor_on(drive)) {
        rel_fdc();
        return -1;
    }

    if (unit[drive].dirty == 1) {
        del_timer (flush_track_timer + drive);
        non_int_flush_track (drive);
    }
    errcnt = 0;
    while (errcnt < MAX_ERRORS) {
        if (!fd_seek(drive, track))
            return -1;
        raw_read(drive);
        error = (*unit[drive].dtype->read_fkt)(drive);
        if (error == 0) {
            rel_fdc();
            return 0;
        }
        /* Read Error Handling: recalibrate and try again */
        unit[drive].track = -1;
        errcnt++;
    }
    rel_fdc();
    return -1;
}

/*
 * Round-robin between our available drives, doing one request from each
 */
static struct request *set_next_request(void)
{
    struct request_queue *q;
    int cnt = FD_MAX_UNITS;
    struct request *rq = NULL;

    /* Find next queue we can dispatch from */
    fdc_queue = fdc_queue + 1;
    if (fdc_queue == FD_MAX_UNITS)
        fdc_queue = 0;

    for(cnt = FD_MAX_UNITS; cnt > 0; cnt--) {

        if (unit[fdc_queue].type->code == FD_NODRIVE) {
            if (++fdc_queue == FD_MAX_UNITS)
                fdc_queue = 0;
            continue;
        }

        q = unit[fdc_queue].gendisk->queue;
        if (q) {
            rq = blk_fetch_request(q);
            if (rq)
                break;
        }

        if (++fdc_queue == FD_MAX_UNITS)
            fdc_queue = 0;
    }

    return rq;
}

static void redo_fd_request(void)
{
    struct request *rq;
    unsigned int cnt, block, track, sector;
    int drive;
    struct amiga_floppy_struct *floppy;
    char *data;
    unsigned long flags;
    int err;

next_req:
    rq = set_next_request();
    if (!rq) {
        /* Nothing left to do */
        return;
    }

    floppy = rq->rq_disk->private_data;
    drive = floppy - unit;

next_segment:
    /* Here someone could investigate to be more efficient */
    for (cnt = 0, err = 0; cnt < blk_rq_cur_sectors(rq); cnt++) {
#ifdef DEBUG
        printk("fd: sector %ld + %d requested for %s\n",
               blk_rq_pos(rq), cnt,
               (rq_data_dir(rq) == READ) ? "read" : "write");
#endif
        block = blk_rq_pos(rq) + cnt;
        if ((int)block > floppy->blocks) {
            err = -EIO;
            break;
        }

        track = block / (floppy->dtype->sects * floppy->type->sect_mult);
        sector = block % (floppy->dtype->sects * floppy->type->sect_mult);
        data = rq->buffer + 512 * cnt;
#ifdef DEBUG
        printk("access to track %d, sector %d, with buffer at "
               "0x%08lx\n", track, sector, data);
#endif

        if (get_track(drive, track) == -1) {
            err = -EIO;
            break;
        }

        if (rq_data_dir(rq) == READ) {
            memcpy(data, floppy->trackbuf + sector * 512, 512);
        } else {
            memcpy(floppy->trackbuf + sector * 512, data, 512);

            /* keep the drive spinning while writes are scheduled */
            if (!fd_motor_on(drive)) {
                err = -EIO;
                break;
            }
            /*
             * setup a callback to write the track buffer
             * after a short (1 tick) delay.
             */
            local_irq_save(flags);

            floppy->dirty = 1;
                /* reset the timer */
            mod_timer (flush_track_timer + drive, jiffies + 1);
            local_irq_restore(flags);
        }
    }

    if (__blk_end_request_cur(rq, err))
        goto next_segment;
    goto next_req;
}

static void do_fd_request(struct request_queue * q)
{
    redo_fd_request();
}

static int fd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
    int drive = MINOR(bdev->bd_dev) & 3;

    geo->heads = unit[drive].type->heads;
    geo->sectors = unit[drive].dtype->sects * unit[drive].type->sect_mult;
    geo->cylinders = unit[drive].type->tracks;
    return 0;
}

static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode,
            unsigned int cmd, unsigned long param)
{
    struct amiga_floppy_struct *p = bdev->bd_disk->private_data;
    int drive = p - unit;
    static struct floppy_struct getprm;
    void __user *argp = (void __user *)param;

    switch(cmd){
    case FDFMTBEG:
        get_fdc(drive);
        if (fd_ref[drive] > 1) {
            rel_fdc();
            return -EBUSY;
        }
        fsync_bdev(bdev);
        if (fd_motor_on(drive) == 0) {
            rel_fdc();
            return -ENODEV;
        }
        if (fd_calibrate(drive) == 0) {
            rel_fdc();
            return -ENXIO;
        }
        floppy_off(drive);
        rel_fdc();
        break;
    case FDFMTTRK:
        if (param < p->type->tracks * p->type->heads)
        {
            get_fdc(drive);
            if (fd_seek(drive,param) != 0){
                memset(p->trackbuf, FD_FILL_BYTE,
                       p->dtype->sects * p->type->sect_mult * 512);
                non_int_flush_track(drive);
            }
            floppy_off(drive);
            rel_fdc();
        }
        else
            return -EINVAL;
        break;
    case FDFMTEND:
        floppy_off(drive);
        invalidate_bdev(bdev);
        break;
    case FDGETPRM:
        memset((void *)&getprm, 0, sizeof (getprm));
        getprm.track=p->type->tracks;
        getprm.head=p->type->heads;
        getprm.sect=p->dtype->sects * p->type->sect_mult;
        getprm.size=p->blocks;
        if (copy_to_user(argp, &getprm, sizeof(struct floppy_struct)))
            return -EFAULT;
        break;
    case FDSETPRM:
    case FDDEFPRM:
        return -EINVAL;
    case FDFLUSH: /* unconditionally, even if not needed */
        del_timer (flush_track_timer + drive);
        non_int_flush_track(drive);
        break;
#ifdef RAW_IOCTL
    case IOCTL_RAW_TRACK:
        if (copy_to_user(argp, raw_buf, p->type->read_size))
            return -EFAULT;
        else
            return p->type->read_size;
#endif
    default:
        printk(KERN_DEBUG "fd_ioctl: unknown cmd %d for drive %d.",
               cmd, drive);
        return -ENOSYS;
    }
    return 0;
}

static int fd_ioctl(struct block_device *bdev, fmode_t mode,
                 unsigned int cmd, unsigned long param)
{
    int ret;

    mutex_lock(&amiflop_mutex);
    ret = fd_locked_ioctl(bdev, mode, cmd, param);
    mutex_unlock(&amiflop_mutex);

    return ret;
}

static void fd_probe(int dev)
{
    unsigned long code;
    int type;
    int drive;

    drive = dev & 3;
    code = fd_get_drive_id(drive);

    /* get drive type */
    for (type = 0; type < num_dr_types; type++)
        if (drive_types[type].code == code)
            break;

    if (type >= num_dr_types) {
        printk(KERN_WARNING "fd_probe: unsupported drive type "
               "%08lx found\n", code);
        unit[drive].type = &drive_types[num_dr_types-1]; /* FD_NODRIVE */
        return;
    }

    unit[drive].type = drive_types + type;
    unit[drive].track = -1;

    unit[drive].disk = -1;
    unit[drive].motor = 0;
    unit[drive].busy = 0;
    unit[drive].status = -1;
}

/*
 * floppy_open check for aliasing (/dev/fd0 can be the same as
 * /dev/PS0 etc), and disallows simultaneous access to the same
 * drive with different device numbers.
 */
static int floppy_open(struct block_device *bdev, fmode_t mode)
{
    int drive = MINOR(bdev->bd_dev) & 3;
    int system =  (MINOR(bdev->bd_dev) & 4) >> 2;
    int old_dev;
    unsigned long flags;

    mutex_lock(&amiflop_mutex);
    old_dev = fd_device[drive];

    if (fd_ref[drive] && old_dev != system) {
        mutex_unlock(&amiflop_mutex);
        return -EBUSY;
    }

    if (mode & (FMODE_READ|FMODE_WRITE)) {
        check_disk_change(bdev);
        if (mode & FMODE_WRITE) {
            int wrprot;

            get_fdc(drive);
            fd_select (drive);
            wrprot = !(ciaa.pra & DSKPROT);
            fd_deselect (drive);
            rel_fdc();

            if (wrprot) {
                mutex_unlock(&amiflop_mutex);
                return -EROFS;
            }
        }
    }

    local_irq_save(flags);
    fd_ref[drive]++;
    fd_device[drive] = system;
    local_irq_restore(flags);

    unit[drive].dtype=&data_types[system];
    unit[drive].blocks=unit[drive].type->heads*unit[drive].type->tracks*
        data_types[system].sects*unit[drive].type->sect_mult;
    set_capacity(unit[drive].gendisk, unit[drive].blocks);

    printk(KERN_INFO "fd%d: accessing %s-disk with %s-layout\n",drive,
           unit[drive].type->name, data_types[system].name);

    mutex_unlock(&amiflop_mutex);
    return 0;
}

static int floppy_release(struct gendisk *disk, fmode_t mode)
{
    struct amiga_floppy_struct *p = disk->private_data;
    int drive = p - unit;

    mutex_lock(&amiflop_mutex);
    if (unit[drive].dirty == 1) {
        del_timer (flush_track_timer + drive);
        non_int_flush_track (drive);
    }
  
    if (!fd_ref[drive]--) {
        printk(KERN_CRIT "floppy_release with fd_ref == 0");
        fd_ref[drive] = 0;
    }
#ifdef MODULE
/* the mod_use counter is handled this way */
    floppy_off (drive | 0x40000000);
#endif
    mutex_unlock(&amiflop_mutex);
    return 0;
}

/*
 * check_events is never called from an interrupt, so we can relax a bit
 * here, sleep etc. Note that floppy-on tries to set current_DOR to point
 * to the desired drive, but it will probably not survive the sleep if
 * several floppies are used at the same time: thus the loop.
 */
static unsigned amiga_check_events(struct gendisk *disk, unsigned int clearing)
{
    struct amiga_floppy_struct *p = disk->private_data;
    int drive = p - unit;
    int changed;
    static int first_time = 1;

    if (first_time)
        changed = first_time--;
    else {
        get_fdc(drive);
        fd_select (drive);
        changed = !(ciaa.pra & DSKCHANGE);
        fd_deselect (drive);
        rel_fdc();
    }

    if (changed) {
        fd_probe(drive);
        p->track = -1;
        p->dirty = 0;
        writepending = 0; /* if this was true before, too bad! */
        writefromint = 0;
        return DISK_EVENT_MEDIA_CHANGE;
    }
    return 0;
}

static const struct block_device_operations floppy_fops = {
    .owner      = THIS_MODULE,
    .open       = floppy_open,
    .release    = floppy_release,
    .ioctl      = fd_ioctl,
    .getgeo     = fd_getgeo,
    .check_events   = amiga_check_events,
};

static int __init fd_probe_drives(void)
{
    int drive,drives,nomem;

    printk(KERN_INFO "FD: probing units\nfound ");
    drives=0;
    nomem=0;
    for(drive=0;drive<FD_MAX_UNITS;drive++) {
        struct gendisk *disk;
        fd_probe(drive);
        if (unit[drive].type->code == FD_NODRIVE)
            continue;
        disk = alloc_disk(1);
        if (!disk) {
            unit[drive].type->code = FD_NODRIVE;
            continue;
        }
        unit[drive].gendisk = disk;

        disk->queue = blk_init_queue(do_fd_request, &amiflop_lock);
        if (!disk->queue) {
            unit[drive].type->code = FD_NODRIVE;
            continue;
        }

        drives++;
        if ((unit[drive].trackbuf = kmalloc(FLOPPY_MAX_SECTORS * 512, GFP_KERNEL)) == NULL) {
            printk("no mem for ");
            unit[drive].type = &drive_types[num_dr_types - 1]; /* FD_NODRIVE */
            drives--;
            nomem = 1;
        }
        printk("fd%d ",drive);
        disk->major = FLOPPY_MAJOR;
        disk->first_minor = drive;
        disk->fops = &floppy_fops;
        sprintf(disk->disk_name, "fd%d", drive);
        disk->private_data = &unit[drive];
        set_capacity(disk, 880*2);
        add_disk(disk);
    }
    if ((drives > 0) || (nomem == 0)) {
        if (drives == 0)
            printk("no drives");
        printk("\n");
        return drives;
    }
    printk("\n");
    return -ENOMEM;
}
 
static struct kobject *floppy_find(dev_t dev, int *part, void *data)
{
    int drive = *part & 3;
    if (unit[drive].type->code == FD_NODRIVE)
        return NULL;
    *part = 0;
    return get_disk(unit[drive].gendisk);
}

static int __init amiga_floppy_probe(struct platform_device *pdev)
{
    int i, ret;

    if (register_blkdev(FLOPPY_MAJOR,"fd"))
        return -EBUSY;

    ret = -ENOMEM;
    raw_buf = amiga_chip_alloc(RAW_BUF_SIZE, "Floppy");
    if (!raw_buf) {
        printk("fd: cannot get chip mem buffer\n");
        goto out_blkdev;
    }

    ret = -EBUSY;
    if (request_irq(IRQ_AMIGA_DSKBLK, fd_block_done, 0, "floppy_dma", NULL)) {
        printk("fd: cannot get irq for dma\n");
        goto out_irq;
    }

    if (request_irq(IRQ_AMIGA_CIAA_TB, ms_isr, 0, "floppy_timer", NULL)) {
        printk("fd: cannot get irq for timer\n");
        goto out_irq2;
    }

    ret = -ENODEV;
    if (fd_probe_drives() < 1) /* No usable drives */
        goto out_probe;

    blk_register_region(MKDEV(FLOPPY_MAJOR, 0), 256, THIS_MODULE,
                floppy_find, NULL, NULL);

    /* initialize variables */
    init_timer(&motor_on_timer);
    motor_on_timer.expires = 0;
    motor_on_timer.data = 0;
    motor_on_timer.function = motor_on_callback;
    for (i = 0; i < FD_MAX_UNITS; i++) {
        init_timer(&motor_off_timer[i]);
        motor_off_timer[i].expires = 0;
        motor_off_timer[i].data = i|0x80000000;
        motor_off_timer[i].function = fd_motor_off;
        init_timer(&flush_track_timer[i]);
        flush_track_timer[i].expires = 0;
        flush_track_timer[i].data = i;
        flush_track_timer[i].function = flush_track_callback;

        unit[i].track = -1;
    }

    init_timer(&post_write_timer);
    post_write_timer.expires = 0;
    post_write_timer.data = 0;
    post_write_timer.function = post_write;
  
    for (i = 0; i < 128; i++)
        mfmdecode[i]=255;
    for (i = 0; i < 16; i++)
        mfmdecode[mfmencode[i]]=i;

    /* make sure that disk DMA is enabled */
    custom.dmacon = DMAF_SETCLR | DMAF_DISK;

    /* init ms timer */
    ciaa.crb = 8; /* one-shot, stop */
    return 0;

out_probe:
    free_irq(IRQ_AMIGA_CIAA_TB, NULL);
out_irq2:
    free_irq(IRQ_AMIGA_DSKBLK, NULL);
out_irq:
    amiga_chip_free(raw_buf);
out_blkdev:
    unregister_blkdev(FLOPPY_MAJOR,"fd");
    return ret;
}

#if 0 /* not safe to unload */
static int __exit amiga_floppy_remove(struct platform_device *pdev)
{
    int i;

    for( i = 0; i < FD_MAX_UNITS; i++) {
        if (unit[i].type->code != FD_NODRIVE) {
            struct request_queue *q = unit[i].gendisk->queue;
            del_gendisk(unit[i].gendisk);
            put_disk(unit[i].gendisk);
            kfree(unit[i].trackbuf);
            if (q)
                blk_cleanup_queue(q);
        }
    }
    blk_unregister_region(MKDEV(FLOPPY_MAJOR, 0), 256);
    free_irq(IRQ_AMIGA_CIAA_TB, NULL);
    free_irq(IRQ_AMIGA_DSKBLK, NULL);
    custom.dmacon = DMAF_DISK; /* disable DMA */
    amiga_chip_free(raw_buf);
    unregister_blkdev(FLOPPY_MAJOR, "fd");
}
#endif

static struct platform_driver amiga_floppy_driver = {
    .driver   = {
        .name   = "amiga-floppy",
        .owner  = THIS_MODULE,
    },
};

static int __init amiga_floppy_init(void)
{
    return platform_driver_probe(&amiga_floppy_driver, amiga_floppy_probe);
}

module_init(amiga_floppy_init);

#ifndef MODULE
static int __init amiga_floppy_setup (char *str)
{
    int n;
    if (!MACH_IS_AMIGA)
        return 0;
    if (!get_option(&str, &n))
        return 0;
    printk (KERN_INFO "amiflop: Setting default df0 to %x\n", n);
    fd_def_df0 = n;
    return 1;
}

__setup("floppy=", amiga_floppy_setup);
#endif

MODULE_ALIAS("platform:amiga-floppy");