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amiflop.c

/*
 *  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 -ENXIO;

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

      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 = -ENXIO;
      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

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