return 0;}/* * Block-driver specific functions *//* * Find the device for this request. */static Spull_Dev *spull_locate_device(const struct request *req){    int devno;    Spull_Dev *device;    /* Check if the minor number is in range */    devno = DEVICE_NR(req->rq_dev);    if (devno >= spull_devs) {        static int count = 0;        if (count++ < 5) /* print the message at most five times */            printk(KERN_WARNING "spull: request for unknown device\n");        return NULL;    }    device = spull_devices + devno;    return device;}/* * Perform an actual transfer. */static int spull_transfer(Spull_Dev *device, const struct request *req){    int size, minor = MINOR(req->rq_dev);    u8 *ptr;        ptr = device->data +            (spull_partitions[minor].start_sect + req->sector)*SPULL_HARDSECT;    size = req->current_nr_sectors*SPULL_HARDSECT;    /*     * Make sure that the transfer fits within the device.     */    if (req->sector + req->current_nr_sectors >                    spull_partitions[minor].nr_sects) {        static int count = 0;        if (count++ < 5)            printk(KERN_WARNING "spull: request past end of partition\n");        return 0;    }    /*     * Looks good, do the transfer.     */    switch(req->cmd) {        case READ:            memcpy(req->buffer, ptr, size); /* from spull to buffer */            return 1;        case WRITE:            memcpy(ptr, req->buffer, size); /* from buffer to spull */            return 1;        default:            /* can't happen */            return 0;        }}#ifdef LINUX_24void spull_request(request_queue_t *q)#else           void spull_request()#endif  {    Spull_Dev *device;    int status;    long flags;    while(1) {        INIT_REQUEST;  /* returns when queue is empty */        /* Which "device" are we using?  (Is returned locked) */        device = spull_locate_device (CURRENT);        if (device == NULL) {            end_request(0);            continue;        }	spin_lock_irqsave(&device->lock, flags);        /* Perform the transfer and clean up. */        status = spull_transfer(device, CURRENT);        spin_unlock_irqrestore(&device->lock, flags);        end_request(status); /* success */    }}/* * The fake interrupt-driven request */struct timer_list spull_timer; /* the engine for async invocation */#ifdef LINUX_24void spull_irqdriven_request(request_queue_t *q)#else                                           void spull_irqdriven_request()                  #endif                                          {    Spull_Dev *device;    int status;    long flags;    /* If we are already processing requests, don't do any more now. */    if (spull_busy)            return;    while(1) {        INIT_REQUEST;  /* returns when queue is empty */        /* Which "device" are we using? */        device = spull_locate_device (CURRENT);        if (device == NULL) {            end_request(0);            continue;        }	spin_lock_irqsave(&device->lock, flags);	        /* Perform the transfer and clean up. */        status = spull_transfer(device, CURRENT);        spin_unlock_irqrestore(&device->lock, flags);        /* ... and wait for the timer to expire -- no end_request(1) */        spull_timer.expires = jiffies + spull_irq;        add_timer(&spull_timer);        spull_busy = 1;        return;    }}/* this is invoked when the timer expires */void spull_interrupt(unsigned long unused){    unsigned long flags;    spin_lock_irqsave(&io_request_lock, flags);    end_request(1);    /* This request is done - we always succeed */    spull_busy = 0;  /* We have io_request_lock, no conflict with request */    if (! QUEUE_EMPTY) /* more of them? */#ifdef LINUX_24                                 spull_irqdriven_request(NULL);  /* Start the next transfer */#else                                           spull_irqdriven_request();      #endif                                      spin_unlock_irqrestore(&io_request_lock, flags);}/* * Finally, the module stuff */int spull_init(void){    int result, i;    /*     * Copy the (static) cfg variables to public prefixed ones to allow     * snoozing with a debugger.     */    spull_major    = major;    spull_devs     = devs;    spull_rahead   = rahead;    spull_size     = size;    spull_blksize  = blksize;    /*     * Register your major, and accept a dynamic number     */    result = register_blkdev(spull_major, "spull", &spull_bdops);    if (result < 0) {        printk(KERN_WARNING "spull: can't get major %d\n",spull_major);        return result;    }    if (spull_major == 0) spull_major = result; /* dynamic */    major = spull_major; /* Use `major' later on to save typing */    spull_gendisk.major = major; /* was unknown at load time */    /*      * allocate the devices -- we can't have them static, as the number     * can be specified at load time     */    spull_devices = kmalloc(spull_devs * sizeof (Spull_Dev), GFP_KERNEL);    if (!spull_devices)        goto fail_malloc;    memset(spull_devices, 0, spull_devs * sizeof (Spull_Dev));    for (i=0; i < spull_devs; i++) {        /* data and usage remain zeroed */        spull_devices[i].size = blksize * spull_size;        init_timer(&(spull_devices[i].timer));        spull_devices[i].timer.data = (unsigned long)(spull_devices+i);        spull_devices[i].timer.function = spull_expires;        spin_lock_init(&spull_devices[i].lock);    }    /*     * Assign the other needed values: request, rahead, size, blksize,     * hardsect. All the minor devices feature the same value.     * Note that `spull' defines all of them to allow testing non-default     * values. A real device could well avoid setting values in global     * arrays if it uses the default values.     */    read_ahead[major] = spull_rahead;    result = -ENOMEM; /* for the possible errors */    spull_sizes = kmalloc( (spull_devs << SPULL_SHIFT) * sizeof(int),                          GFP_KERNEL);    if (!spull_sizes)        goto fail_malloc;    /* Start with zero-sized partitions, and correctly sized units */    memset(spull_sizes, 0, (spull_devs << SPULL_SHIFT) * sizeof(int));    for (i=0; i< spull_devs; i++)        spull_sizes[i<<SPULL_SHIFT] = spull_size;    blk_size[MAJOR_NR] = spull_gendisk.sizes = spull_sizes;    /* Allocate the partitions array. */    spull_partitions = kmalloc( (spull_devs << SPULL_SHIFT) *                               sizeof(struct hd_struct), GFP_KERNEL);    if (!spull_partitions)        goto fail_malloc;    memset(spull_partitions, 0, (spull_devs << SPULL_SHIFT) *           sizeof(struct hd_struct));    /* fill in whole-disk entries */    for (i=0; i < spull_devs; i++)         spull_partitions[i << SPULL_SHIFT].nr_sects =		spull_size*(blksize/SPULL_HARDSECT);    spull_gendisk.part = spull_partitions;    spull_gendisk.nr_real = spull_devs;#ifndef LINUX_24    spull_gendisk.max_nr = spull_devs;#endif    /*     * Put our gendisk structure on the list.     */    spull_gendisk.next = gendisk_head;    gendisk_head = &spull_gendisk;     /* dump the partition table to see it */    for (i=0; i < spull_devs << SPULL_SHIFT; i++)        PDEBUGG("part %i: beg %lx, size %lx\n", i,               spull_partitions[i].start_sect,               spull_partitions[i].nr_sects);    /*     * Allow interrupt-driven operation, if "irq=" has been specified     */    spull_irq = irq; /* copy the static variable to the visible one */    if (spull_irq) {        PDEBUG("setting timer\n");        spull_timer.function = spull_interrupt;        blk_init_queue(BLK_DEFAULT_QUEUE(major), spull_irqdriven_request);    }    else        blk_init_queue(BLK_DEFAULT_QUEUE(major), spull_request);#ifdef NOTNOW    for (i = 0; i < spull_devs; i++)            register_disk(NULL, MKDEV(major, i), 1, &spull_bdops,                            spull_size << 1);#endif#ifndef SPULL_DEBUG    EXPORT_NO_SYMBOLS; /* otherwise, leave global symbols visible */#endif    printk ("<1>spull: init complete, %d devs, size %d blks %d\n",                    spull_devs, spull_size, spull_blksize);    return 0; /* succeed */  fail_malloc:    read_ahead[major] = 0;    if (spull_sizes) kfree(spull_sizes);    if (spull_partitions) kfree(spull_partitions);    blk_size[major] = NULL;    if (spull_devices) kfree(spull_devices);    unregister_blkdev(major, "spull");    return result;}void spull_cleanup(void){    int i;    struct gendisk **gdp;/* * Before anything else, get rid of the timer functions.  Set the "usage" * flag on each device as well, under lock, so that if the timer fires up * just before we delete it, it will either complete or abort.  Otherwise * we have nasty race conditions to worry about. */    for (i = 0; i < spull_devs; i++) {        Spull_Dev *dev = spull_devices + i;        del_timer(&dev->timer);        spin_lock(&dev->lock);        dev->usage++;        spin_unlock(&dev->lock);    }    /* flush it all and reset all the data structures *//* * Unregister the device now to avoid further operations during cleanup. */    unregister_blkdev(major, "spull");    for (i = 0; i < (spull_devs << SPULL_SHIFT); i++)        fsync_dev(MKDEV(spull_major, i)); /* flush the devices */    blk_cleanup_queue(BLK_DEFAULT_QUEUE(major));    read_ahead[major] = 0;    kfree(blk_size[major]); /* which is gendisk->sizes as well */    blk_size[major] = NULL;    kfree(spull_gendisk.part);    kfree(blksize_size[major]);    blksize_size[major] = NULL;    /*     * Get our gendisk structure off the list.     */    for (gdp = &gendisk_head; *gdp; gdp = &((*gdp)->next))        if (*gdp == &spull_gendisk) {            *gdp = (*gdp)->next;            break;        }    /* finally, the usual cleanup */    for (i=0; i < spull_devs; i++) {        if (spull_devices[i].data)            vfree(spull_devices[i].data);    }    kfree(spull_devices);}module_init(spull_init);module_exit(spull_cleanup);