spull.c

本源码是将述嵌入式LINUX驱动程序例程

    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_24
void 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_24
void 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);