sbull.c
/*
 * Sample disk driver, from the beginning.
 */
 
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
 
#include <linux/sched.h>
#include <linux/kernel.h>   /* printk() */
#include <linux/slab.h>     /* kmalloc() */
#include <linux/fs.h>       /* everything... */
#include <linux/errno.h>    /* error codes */
#include <linux/timer.h>
#include <linux/types.h>    /* size_t */
#include <linux/fcntl.h>    /* O_ACCMODE */
#include <linux/hdreg.h>    /* HDIO_GETGEO */
#include <linux/kdev_t.h>
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>  /* invalidate_bdev */
#include <linux/bio.h>
 
MODULE_LICENSE("Dual BSD/GPL");
 
static int sbull_major = 0;
module_param(sbull_major, int, 0);
static int hardsect_size = 512;
module_param(hardsect_size, int, 0);
static int nsectors = 8192; // 1024; /* How big the drive is */
module_param(nsectors, int, 0);
static int ndevices = 1;
module_param(ndevices, int, 0);
 
/*
 * The different "request modes" we can use.
 */
enum {
    RM_SIMPLE  = 0, /* The extra-simple request function */
    RM_FULL    = 1, /* The full-blown version */
    RM_NOQUEUE = 2, /* Use make_request */
};
static int request_mode = RM_SIMPLE;
module_param(request_mode, int, 0);
 
/*
 * Minor number and partition management.
 */
#define SBULL_MINORS    16
#define MINOR_SHIFT 4
#define DEVNUM(kdevnum) (MINOR(kdev_t_to_nr(kdevnum)) >> MINOR_SHIFT
 
/*
 * We can tweak our hardware sector size, but the kernel talks to us
 * in terms of small sectors, always.
 */
#define KERNEL_SECTOR_SIZE  512
 
/*
 * After this much idle time, the driver will simulate a media change.
 */
#define INVALIDATE_DELAY    30*HZ
 
/*
 * The internal representation of our device.
 */
struct sbull_dev {
        int size;                       /* Device size in sectors */
        u8 *data;                       /* The data array */
        short users;                    /* How many users */
        short media_change;             /* Flag a media change? */
        spinlock_t lock;                /* For mutual exclusion */
        struct request_queue *queue;    /* The device request queue */
        struct gendisk *gd;             /* The gendisk structure */
        struct timer_list timer;        /* For simulated media changes */
};
 
static struct sbull_dev *Devices = NULL;
 
/*
 * Handle an I/O request.
 */
static void sbull_transfer(struct sbull_dev *dev, unsigned long sector,
        unsigned long nsect, char *buffer, int write)
{
    unsigned long offset = sector*KERNEL_SECTOR_SIZE;
    unsigned long nbytes = nsect*KERNEL_SECTOR_SIZE;
 
    if ((offset + nbytes) > dev->size) {
        printk (KERN_NOTICE "Beyond-end write (%ld %ld)\n", offset, nbytes);
        return;
    }
    if (write)
        memcpy(dev->data + offset, buffer, nbytes);
    else
        memcpy(buffer, dev->data + offset, nbytes);
}
 
/*
 * The simple form of the request function.
 */
static void sbull_request(struct request_queue *q)
{
    struct request *req;
 
    while ((req = elv_next_request(q)) != NULL) {
        struct sbull_dev *dev = req->rq_disk->private_data;
        if (! blk_fs_request(req)) {
            printk (KERN_NOTICE "Skip non-fs request\n");
            end_request(req, 0);
            continue;
        }
    //      printk (KERN_NOTICE "Req dev %d dir %ld sec %ld, nr %d f %lx\n",
    //              dev - Devices, rq_data_dir(req),
    //              req->sector, req->current_nr_sectors,
    //              req->flags);
        sbull_transfer(dev, req->sector, req->current_nr_sectors,
                req->buffer, rq_data_dir(req));
        end_request(req, 1);
    }
}
 
/*
 * Open and close.
 */
 
static int sbull_open(struct inode *inode, struct file *filp)
{
    struct sbull_dev *dev = inode->i_bdev->bd_disk->private_data;
 
    del_timer_sync(&dev->timer);
    filp->private_data = dev;
    spin_lock(&dev->lock);
    if (! dev->users) 
        check_disk_change(inode->i_bdev);
    dev->users++;
    spin_unlock(&dev->lock);
    return 0;
}
 
static int sbull_release(struct inode *inode, struct file *filp)
{
    struct sbull_dev *dev = inode->i_bdev->bd_disk->private_data;
 
    spin_lock(&dev->lock);
    dev->users--;
 
    if (!dev->users) {
        dev->timer.expires = jiffies + INVALIDATE_DELAY;
        add_timer(&dev->timer);
    }
    spin_unlock(&dev->lock);
 
    return 0;
}
 
/*
 * Look for a (simulated) media change.
 */
int sbull_media_changed(struct gendisk *gd)
{
    struct sbull_dev *dev = gd->private_data;
 
    return dev->media_change;
}
 
/*
 * Revalidate.  WE DO NOT TAKE THE LOCK HERE, for fear of deadlocking
 * with open.  That needs to be reevaluated.
 */
int sbull_revalidate(struct gendisk *gd)
{
    struct sbull_dev *dev = gd->private_data;
 
    if (dev->media_change) {
        dev->media_change = 0;
        memset (dev->data, 0, dev->size);
    }
    return 0;
}
 
/*
 * The "invalidate" function runs out of the device timer; it sets
 * a flag to simulate the removal of the media.
 */
void sbull_invalidate(unsigned long ldev)
{
    struct sbull_dev *dev = (struct sbull_dev *) ldev;
 
    spin_lock(&dev->lock);
    if (dev->users || !dev->data) 
        printk (KERN_WARNING "sbull: timer sanity check failed\n");
    else
        dev->media_change = 1;
    spin_unlock(&dev->lock);
}
 
/*
 * The ioctl() implementation
 */
 
int sbull_ioctl (struct inode *inode, struct file *filp,
                 unsigned int cmd, unsigned long arg)
{
    long size;
    struct hd_geometry geo;
    struct sbull_dev *dev = filp->private_data;
 
    switch(cmd) {
        case HDIO_GETGEO:
            /*
         * Get geometry: since we are a virtual device, we have to make
         * up something plausible.  So we claim 16 sectors, four heads,
         * and calculate the corresponding number of cylinders.  We set the
         * start of data at sector four.
         */
        size = dev->size*(hardsect_size/KERNEL_SECTOR_SIZE);
        geo.cylinders = (size & ~0x3f) >> 6;
        geo.heads = 4;
        geo.sectors = 16;
        geo.start = 4;
        if (copy_to_user((void __user *) arg, &geo, sizeof(geo)))
            return -EFAULT;
    printk(KERN_INFO "sbull HDIO_GETGEO: C=%d H=%d S=%d\n",
        geo.cylinders, geo.heads, geo.sectors);
        return 0;
    }
 
    return -ENOTTY; /* unknown command */
}
 
/*
 * The device operations structure.
 */
static struct block_device_operations sbull_ops = {
    .owner           = THIS_MODULE,
    .open            = sbull_open,
    .release     = sbull_release,
    .media_changed   = sbull_media_changed,
    .revalidate_disk = sbull_revalidate,
    .ioctl           = sbull_ioctl
};
 
/*
 * Set up our internal device.
 */
static void setup_device(struct sbull_dev *dev, int which)
{
    /*
     * Get some memory.
     */
    memset (dev, 0, sizeof (struct sbull_dev));
    dev->size = nsectors*hardsect_size;
    dev->data = vmalloc(dev->size);
    if (dev->data == NULL) {
        printk (KERN_NOTICE "vmalloc failure.\n");
        return;
    }
    spin_lock_init(&dev->lock);
 
    /*
     * The timer which "invalidates" the device.
     */
    init_timer(&dev->timer);
    dev->timer.data = (unsigned long) dev;
    dev->timer.function = sbull_invalidate;
 
    /*
     * The I/O queue, depending on whether we are using our own
     * make_request function or not.
     */
    switch (request_mode) {
        default:
        printk(KERN_NOTICE "Bad request mode %d, using simple\n", request_mode);
            /* fall into.. */
 
        case RM_SIMPLE:
        dev->queue = blk_init_queue(sbull_request, &dev->lock);
        if (dev->queue == NULL)
            goto out_vfree;
        break;
    }
    blk_queue_hardsect_size(dev->queue, hardsect_size);
    dev->queue->queuedata = dev;
    /*
     * And the gendisk structure.
     */
    dev->gd = alloc_disk(SBULL_MINORS);
    if (! dev->gd) {
        printk (KERN_NOTICE "alloc_disk failure\n");
        goto out_vfree;
    }
    dev->gd->major = sbull_major;
    dev->gd->first_minor = which*SBULL_MINORS;
    dev->gd->fops = &sbull_ops;
    dev->gd->queue = dev->queue;
    dev->gd->private_data = dev;
    snprintf (dev->gd->disk_name, 32, "sbull%c", which + 'a');
    set_capacity(dev->gd, nsectors*(hardsect_size/KERNEL_SECTOR_SIZE));
    add_disk(dev->gd);
    return;
 
  out_vfree:
    if (dev->data)
        vfree(dev->data);
}
 
static int __init sbull_init(void)
{
    int i;
    /*
     * Get registered.
     */
    sbull_major = register_blkdev(sbull_major, "sbull");
    if (sbull_major <= 0) {
        printk(KERN_WARNING "sbull: unable to get major number\n");
        return -EBUSY;
    }
    /*
     * Allocate the device array, and initialize each one.
     */
    Devices = kmalloc(ndevices*sizeof (struct sbull_dev), GFP_KERNEL);
    if (Devices == NULL)
        goto out_unregister;
    for (i = 0; i < ndevices; i++) 
        setup_device(Devices + i, i);
 
    return 0;
 
  out_unregister:
    unregister_blkdev(sbull_major, "sbd");
    return -ENOMEM;
}
 
static void sbull_exit(void)
{
    int i;
 
    for (i = 0; i < ndevices; i++) {
        struct sbull_dev *dev = Devices + i;
 
        del_timer_sync(&dev->timer);
        if (dev->gd) {
            del_gendisk(dev->gd);
            put_disk(dev->gd);
        }
        if (dev->queue) {
                blk_cleanup_queue(dev->queue);
        }
        if (dev->data)
            vfree(dev->data);
    }
    unregister_blkdev(sbull_major, "sbull");
    kfree(Devices);
}
 
module_init(sbull_init);
module_exit(sbull_exit);
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