/*
 *  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/fd.h>
#include <linux/hdreg.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/amifdreg.h>
#include <linux/amifd.h>
#include <linux/buffer_head.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/interrupt.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 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");

static struct request_queue *floppy_queue;
#define QUEUE (floppy_queue)
#define CURRENT elv_next_request(floppy_queue)

/*
 *  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_WAIT_QUEUE_HEAD(motor_wait);

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

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

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 volatile int ms_busy = -1;
static DECLARE_WAIT_QUEUE_HEAD(ms_wait);
#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)
{
        ms_busy = -1;
        wake_up(&ms_wait);
        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)
{
        unsigned long flags;
        int ticks;
        if (ms > 0) {
                local_irq_save(flags);
                while (ms_busy == 0)
                        sleep_on(&ms_wait);
                ms_busy = 0;
                local_irq_restore(flags);
                ticks = MS_TICKS*ms-1;
                ciaa.tblo=ticks%256;
                ciaa.tbhi=ticks/256;
                ciaa.crb=0x19; /*count eclock, force load, one-shoot, start */
                sleep_on(&ms_wait);
        }
}

/* 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);
        while (!try_fdc(drive))
                sleep_on(&fdc_wait);
        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) {
                wake_up (&motor_wait);
        } 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);

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

                on_attempts = 10;
                sleep_on (&motor_wait);
                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);
        while (block_flag)
                sleep_on(&wait_fd_block);
        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;

        while (block_flag)
                sleep_on (&wait_fd_block);

        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;
        }
        while (block_flag)
                sleep_on(&wait_fd_block);
        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;
                }
                while (block_flag == 2)
                        sleep_on (&wait_fd_block);
        }
        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;
}

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

 repeat:
        if (!CURRENT) {
                /* Nothing left to do */
                return;
        }

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

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

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

                if ((rq_data_dir(CURRENT) != READ) && (rq_data_dir(CURRENT) != WRITE)) {
                        printk(KERN_WARNING "do_fd_request: unknown command\n");
                        end_request(CURRENT, 0);
                        goto repeat;
                }
                if (get_track(drive, track) == -1) {
                        end_request(CURRENT, 0);
                        goto repeat;
                }

                switch (rq_data_dir(CURRENT)) {
                case READ:
                        memcpy(data, floppy->trackbuf + sector * 512, 512);
                        break;

                case WRITE:
                        memcpy(floppy->trackbuf + sector * 512, data, 512);

                        /* keep the drive spinning while writes are scheduled */
                        if (!fd_motor_on(drive)) {
                                end_request(CURRENT, 0);
                                goto repeat;
                        }
                        /*
                         * 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);
                        break;
                }
        }
        CURRENT->nr_sectors -= CURRENT->current_nr_sectors;
        CURRENT->sector += CURRENT->current_nr_sectors;

        end_request(CURRENT, 1);
        goto repeat;
}

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_ioctl(struct inode *inode, struct file *filp,
                    unsigned int cmd, unsigned long param)
{
        int drive = iminor(inode) & 3;
        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(inode->i_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 < unit[drive].type->tracks * unit[drive].type->heads)
                {
                        get_fdc(drive);
                        if (fd_seek(drive,param) != 0){
                                memset(unit[drive].trackbuf, FD_FILL_BYTE,
                                       unit[drive].dtype->sects * unit[drive].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(inode->i_bdev);
                break;
        case FDGETPRM:
                memset((void *)&getprm, 0, sizeof (getprm));
                getprm.track=unit[drive].type->tracks;
                getprm.head=unit[drive].type->heads;
                getprm.sect=unit[drive].dtype->sects * unit[drive].type->sect_mult;
                getprm.size=unit[drive].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, unit[drive].type->read_size))
                        return -EFAULT;
                else
                        return unit[drive].type->read_size;
#endif
        default:
                printk(KERN_DEBUG "fd_ioctl: unknown cmd %d for drive %d.",
                       cmd, drive);
                return -ENOSYS;
        }
        return 0;
}

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 inode *inode, struct file *filp)
{
        int drive = iminor(inode) & 3;
        int system =  (iminor(inode) & 4) >> 2;
        int old_dev;
        unsigned long flags;

        old_dev = fd_device[drive];

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

        if (filp && filp->f_mode & 3) {
                check_disk_change(inode->i_bdev);
                if (filp->f_mode & 2 ) {
                        int wrprot;

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

                        if (wrprot)
                                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);

        return 0;
}

static int floppy_release(struct inode * inode, struct file * filp)
{
        int drive = iminor(inode) & 3;

        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
        return 0;
}

/*
 * floppy-change 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 int amiga_floppy_change(struct gendisk *disk)
{
        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 1;
        }
        return 0;
}

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

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

        printk(KERN_INFO "FD: probing units\n" KERN_INFO "found ");
        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;
                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];
                disk->queue = floppy_queue;
                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_init(void)
{
        int i, ret;

        if (!MACH_IS_AMIGA)
                return -ENODEV;

        if (!AMIGAHW_PRESENT(AMI_FLOPPY))
                return -ENODEV;

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

        /*
         *  We request DSKPTR, DSKLEN and DSKDATA only, because the other
         *  floppy registers are too spreaded over the custom register space
         */
        ret = -EBUSY;
        if (!request_mem_region(CUSTOM_PHYSADDR+0x20, 8, "amiflop [Paula]")) {
                printk("fd: cannot get floppy registers\n");
                goto out_blkdev;
        }

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

        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 = -ENOMEM;
        floppy_queue = blk_init_queue(do_fd_request, &amiflop_lock);
        if (!floppy_queue)
                goto out_queue;

        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:
        blk_cleanup_queue(floppy_queue);
out_queue:
        free_irq(IRQ_AMIGA_CIAA_TB, NULL);
out_irq2:
        free_irq(IRQ_AMIGA_DSKBLK, NULL);
out_irq:
        amiga_chip_free(raw_buf);
out_memregion:
        release_mem_region(CUSTOM_PHYSADDR+0x20, 8);
out_blkdev:
        unregister_blkdev(FLOPPY_MAJOR,"fd");
        return ret;
}

module_init(amiga_floppy_init);
#ifdef MODULE

#if 0 /* not safe to unload */
void cleanup_module(void)
{
        int i;

        for( i = 0; i < FD_MAX_UNITS; i++) {
                if (unit[i].type->code != FD_NODRIVE) {
                        del_gendisk(unit[i].gendisk);
                        put_disk(unit[i].gendisk);
                        kfree(unit[i].trackbuf);
                }
        }
        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);
        blk_cleanup_queue(floppy_queue);
        release_mem_region(CUSTOM_PHYSADDR+0x20, 8);
        unregister_blkdev(FLOPPY_MAJOR, "fd");
}
#endif

#else
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