sbull.c

本源码是将述嵌入式LINUX驱动程序例程

#endif                                  
{
    while(1) {
        INIT_REQUEST;
        printk("<1>request %p: cmd %i sec %li (nr. %li)\n", CURRENT,
               CURRENT->cmd,
               CURRENT->sector,
               CURRENT->current_nr_sectors);
        end_request(1); /* success */
    }
}


#elif defined(SBULL_MULTIQUEUE)  /* 2.4 only */

/*
 * Clean up this request.
 */
int sbull_end_request(struct request *req, int status)
{
    if (end_that_request_first(req, status, DEVICE_NAME))
        return 1;
    end_that_request_last(req);
    return 0;
}



void sbull_request(request_queue_t *q)
{
    Sbull_Dev *device;
    struct request *req;
    int status;

    /* Find our device */
    device = sbull_locate_device (blkdev_entry_next_request(&q->queue_head));
    if (device->busy) /* no race here - io_request_lock held */
        return;
    device->busy = 1;

    /* Process requests in the queue */
    while(! list_empty(&q->queue_head)) {

    /* Pull the next request off the list. */
        req = blkdev_entry_next_request(&q->queue_head);
        blkdev_dequeue_request(req);
        spin_unlock_irq (&io_request_lock);
        spin_lock(&device->lock);

    /* Process all of the buffers in this (possibly clustered) request. */
        do {
            status = sbull_transfer(device, req);
        } while (end_that_request_first(req, status, DEVICE_NAME));
        spin_unlock(&device->lock);
        spin_lock_irq (&io_request_lock);
        end_that_request_last(req);
    }
    device->busy = 0;
}

/*
 * Tell the block layer where to queue a request.
 */
request_queue_t *sbull_find_queue(kdev_t device)
{
    int devno = DEVICE_NR(device);

    if (devno >= sbull_devs) {
        static int count = 0;
        if (count++ < 5) /* print the message at most five times */
            printk(KERN_WARNING "sbull: request for unknown device\n");
        return NULL;
    }
    return &sbull_devices[devno].queue;
}



#else /* not SBULL_MULTIQUEUE */
#ifdef LINUX_24                                 
void sbull_request(request_queue_t *q)
#else                                           
void sbull_request()                            
#endif                                          
{
    Sbull_Dev *device;
    int status;

    while(1) {
        INIT_REQUEST;  /* returns when queue is empty */

        /* Which "device" are we using? */
        device = sbull_locate_device (CURRENT);
        if (device == NULL) {
            end_request(0);
            continue;
        }

        /* Perform the transfer and clean up. */
	spin_lock(&device->lock);
        status = sbull_transfer(device, CURRENT);
        spin_unlock(&device->lock);
        end_request(status); 
    }
}
#endif /* not SBULL_EMPTY_REQUEST nor SBULL_MULTIQUEUE */

/*
 * Finally, the module stuff
 */

int sbull_init(void)
{
    int result, i;

    /*
     * Copy the (static) cfg variables to public prefixed ones to allow
     * snoozing with a debugger.
     */

    sbull_major    = major;
    sbull_devs     = devs;
    sbull_rahead   = rahead;
    sbull_size     = size;
    sbull_blksize  = blksize;
    sbull_hardsect = hardsect;

#ifdef LINUX_20
    /* Hardsect can't be changed :( */
    if (hardsect != 512) {
        printk(KERN_ERR "sbull: can't change hardsect size\n");
        hardsect = sbull_hardsect = 512;
    }
#endif
    /*
     * Register your major, and accept a dynamic number
     */
    result = register_blkdev(sbull_major, "sbull", &sbull_bdops);
    if (result < 0) {
        printk(KERN_WARNING "sbull: can't get major %d\n",sbull_major);
        return result;
    }
    if (sbull_major == 0) sbull_major = result; /* dynamic */
    major = sbull_major; /* Use `major' later on to save typing */

    /*
     * Assign the other needed values: request, rahead, size, blksize,
     * hardsect. All the minor devices feature the same value.
     * Note that `sbull' 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] = sbull_rahead;
    result = -ENOMEM; /* for the possible errors */

    sbull_sizes = kmalloc(sbull_devs * sizeof(int), GFP_KERNEL);
    if (!sbull_sizes)
        goto fail_malloc;
    for (i=0; i < sbull_devs; i++) /* all the same size */
        sbull_sizes[i] = sbull_size;
    blk_size[major]=sbull_sizes;

    sbull_blksizes = kmalloc(sbull_devs * sizeof(int), GFP_KERNEL);
    if (!sbull_blksizes)
        goto fail_malloc;
    for (i=0; i < sbull_devs; i++) /* all the same blocksize */
        sbull_blksizes[i] = sbull_blksize;
    blksize_size[major]=sbull_blksizes;

    sbull_hardsects = kmalloc(sbull_devs * sizeof(int), GFP_KERNEL);
    if (!sbull_hardsects)
        goto fail_malloc;
    for (i=0; i < sbull_devs; i++) /* all the same hardsect */
        sbull_hardsects[i] = sbull_hardsect;
    hardsect_size[major]=sbull_hardsects;

    /* FIXME: max_readahead and max_sectors */ 
    
    /* 
     * allocate the devices -- we can't have them static, as the number
     * can be specified at load time
     */

    sbull_devices = kmalloc(sbull_devs * sizeof (Sbull_Dev), GFP_KERNEL);
    if (!sbull_devices)
        goto fail_malloc;
    memset(sbull_devices, 0, sbull_devs * sizeof (Sbull_Dev));
    for (i=0; i < sbull_devs; i++) {
        /* data and usage remain zeroed */
        sbull_devices[i].size = 1024 * sbull_size;
        init_timer(&(sbull_devices[i].timer));
        sbull_devices[i].timer.data = (unsigned long)(sbull_devices+i);
        sbull_devices[i].timer.function = sbull_expires;
        spin_lock_init(&sbull_devices[i].lock);
    }

    /*
     * Get the queue set up, and register our (nonexistent) partitions.
     */  
#ifdef SBULL_MULTIQUEUE
    for (i = 0; i < sbull_devs; i++) {
        blk_init_queue(&sbull_devices[i].queue, sbull_request);
        blk_queue_headactive(&sbull_devices[i].queue, 0);
    }
    blk_dev[major].queue = sbull_find_queue;
#else
#  ifdef LINUX_24
    if (noqueue)
        blk_queue_make_request(BLK_DEFAULT_QUEUE(major), sbull_make_request);
    else
#  endif /* LINUX_24 */
        blk_init_queue(BLK_DEFAULT_QUEUE(major), sbull_request);
#endif
    /* A no-op in 2.4.0, but all drivers seem to do it anyway */
    for (i = 0; i < sbull_devs; i++)
            register_disk(NULL, MKDEV(major, i), 1, &sbull_bdops,
                            sbull_size << 1);

#ifndef SBULL_DEBUG
    EXPORT_NO_SYMBOLS; /* otherwise, leave global symbols visible */
#endif

    printk ("<1>sbull: init complete, %d devs, size %d blks %d hs %d\n",
                    sbull_devs, sbull_size, sbull_blksize, sbull_hardsect);
#ifdef SBULL_MULTIQUEUE
    printk ("<1>sbull: Using multiqueue request\n");
#elif defined(LINUX_24)
    if (noqueue)
            printk (KERN_INFO "sbull: using direct make_request\n");
#endif

#ifdef DO_RAW_INTERFACE
    sbullr_init();
#endif
    return 0; /* succeed */

  fail_malloc:
    read_ahead[major] = 0;
    if (sbull_sizes) kfree(sbull_sizes);
    blk_size[major] = NULL;
    if (sbull_blksizes) kfree(sbull_blksizes);
    blksize_size[major] = NULL;
    if (sbull_hardsects) kfree(sbull_hardsects);
    hardsect_size[major] = NULL;
    if (sbull_devices) kfree(sbull_devices);

    unregister_blkdev(major, "sbull");
    return result;
}

void sbull_cleanup(void)
{
    int i;

/*
 * 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 < sbull_devs; i++) {
        Sbull_Dev *dev = sbull_devices + i;
        del_timer(&dev->timer);
        spin_lock(&dev->lock);
        dev->usage++;
        spin_unlock(&dev->lock);
    }

#ifdef DO_RAW_INTERFACE
    sbullr_release();
#endif
    
    /* flush it all and reset all the data structures */


    for (i=0; i<sbull_devs; i++)
        fsync_dev(MKDEV(sbull_major, i)); /* flush the devices */
    unregister_blkdev(major, "sbull");
/*
 * Fix up the request queue(s)
 */
#ifdef SBULL_MULTIQUEUE
    for (i = 0; i < sbull_devs; i++)
            blk_cleanup_queue(&sbull_devices[i].queue);
    blk_dev[major].queue = NULL;
#else
    blk_cleanup_queue(BLK_DEFAULT_QUEUE(major));
#endif   

    /* Clean up the global arrays */
    read_ahead[major] = 0;
    kfree(blk_size[major]);
    blk_size[major] = NULL;
    kfree(blksize_size[major]);
    blksize_size[major] = NULL;
    kfree(hardsect_size[major]);
    hardsect_size[major] = NULL;
    /* FIXME: max_readahead and max_sectors */ 


    /* finally, the usual cleanup */
    for (i=0; i < sbull_devs; i++) {
        if (sbull_devices[i].data)
            vfree(sbull_devices[i].data);
    }
    kfree(sbull_devices);
}



/*
 * Below here is the "raw device" implementation, available only
 * in 2.4.
 */
#ifdef DO_RAW_INTERFACE

/*
 * Transfer an iovec
 */
static int sbullr_rw_iovec(Sbull_Dev *dev, struct kiobuf *iobuf, int rw,
                int sector, int nsectors)
{
    struct request fakereq;
    struct page *page;
    int offset = iobuf->offset, ndone = 0, pageno, result;

    /* Perform I/O on each sector */
    fakereq.sector = sector;
    fakereq.current_nr_sectors = 1;
    fakereq.cmd = rw;
    
    for (pageno = 0; pageno < iobuf->nr_pages; pageno++) {
        page = iobuf->maplist[pageno];
        while (ndone < nsectors) {
            /* Fake up a request structure for the operation */
            fakereq.buffer = (void *) (kmap(page) + offset);
            result = sbull_transfer(dev, &fakereq);
	    kunmap(page);
            if (result == 0)
                return ndone;
            /* Move on to the next one */
            ndone++;
            fakereq.sector++;
            offset += SBULLR_SECTOR;
            if (offset >= PAGE_SIZE) {
                offset = 0;
                break;
            }
        }
    }
    return ndone;
}


/*
 * Handle actual transfers of data.
 */
static int sbullr_transfer (Sbull_Dev *dev, char *buf, size_t count,
                loff_t *offset, int rw)
{
    struct kiobuf *iobuf;       
    int result;
    
    /* Only block alignment and size allowed */
    if ((*offset & SBULLR_SECTOR_MASK) || (count & SBULLR_SECTOR_MASK))
        return -EINVAL;
    if ((unsigned long) buf & SBULLR_SECTOR_MASK)
        return -EINVAL;

    /* Allocate an I/O vector */
    result = alloc_kiovec(1, &iobuf);
    if (result)
        return result;

    /* Map the user I/O buffer and do the I/O. */
    result = map_user_kiobuf(rw, iobuf, (unsigned long) buf, count);
    if (result) {
        free_kiovec(1, &iobuf);
        return result;
    }
    spin_lock(&dev->lock);
    result = sbullr_rw_iovec(dev, iobuf, rw, *offset >> SBULLR_SECTOR_SHIFT,
                    count >> SBULLR_SECTOR_SHIFT);
    spin_unlock(&dev->lock);

    /* Clean up and return. */
    unmap_kiobuf(iobuf);
    free_kiovec(1, &iobuf);
    if (result > 0)
        *offset += result << SBULLR_SECTOR_SHIFT;
    return result << SBULLR_SECTOR_SHIFT;
}


/*
 * Read and write syscalls.
 */
ssize_t sbullr_read(struct file *filp, char *buf, size_t size, loff_t *off)
{
    Sbull_Dev *dev = sbull_devices + MINOR(filp->f_dentry->d_inode->i_rdev);
    return sbullr_transfer(dev, buf, size, off, READ);
}

ssize_t sbullr_write(struct file *filp, const char *buf, size_t size,
                loff_t *off)
{
    Sbull_Dev *dev = sbull_devices + MINOR(filp->f_dentry->d_inode->i_rdev);
    return sbullr_transfer(dev, (char *) buf, size, off, WRITE);
}


static int sbullr_registered = 0;
static struct file_operations sbullr_fops = {
   read:        sbullr_read,
   write:       sbullr_write,
   open:        sbull_open,
   release:     sbull_release,
   ioctl:	sbull_ioctl,
};


static void sbullr_init()
{
    int result;
        
    /* Simplify the math */
    if (sbull_hardsect != SBULLR_SECTOR) {
        printk(KERN_NOTICE "Sbullr requires hardsect = %d\n", SBULLR_SECTOR);
        return;
    }
    SET_MODULE_OWNER(&sbullr_fops);
    result = register_chrdev(sbullr_major, "sbullr", &sbullr_fops);
    if (result >= 0)
        sbullr_registered = 1;
    if (sbullr_major == 0)
        sbullr_major = result;
}


static void sbullr_release()
{
    if (sbullr_registered)
        unregister_chrdev(sbullr_major, "sbullr");
}




#endif /* DO_RAW_INTERFACE */

module_init(sbull_init);
module_exit(sbull_cleanup);