}    if (count > quantum - q_pos)        count = quantum - q_pos; /* write only up to the end of this quantum */    if (copy_from_user (dptr->data[s_pos]+q_pos, buf, count)) {        retval = -EFAULT;        goto nomem;    }    *f_pos += count;     /* update the size */    if (dev->size < *f_pos)        dev->size = *f_pos;    up (&dev->sem);    return count;  nomem:    up (&dev->sem);    return retval;}/* * The ioctl() implementation */int scullv_ioctl (struct inode *inode, struct file *filp,                 unsigned int cmd, unsigned long arg){    int err= 0, ret = 0, tmp;    /* don't even decode wrong cmds: better returning  ENOTTY than EFAULT */    if (_IOC_TYPE(cmd) != SCULLV_IOC_MAGIC) return -ENOTTY;    if (_IOC_NR(cmd) > SCULLV_IOC_MAXNR) return -ENOTTY;    /*     * the type is a bitmask, and VERIFY_WRITE catches R/W     * transfers. Note that the type is user-oriented, while     * verify_area is kernel-oriented, so the concept of "read" and     * "write" is reversed     */    if (_IOC_DIR(cmd) & _IOC_READ)        err = !access_ok(VERIFY_WRITE, (void *)arg, _IOC_SIZE(cmd));    else if (_IOC_DIR(cmd) & _IOC_WRITE)        err =  !access_ok(VERIFY_READ, (void *)arg, _IOC_SIZE(cmd));    if (err) return -EFAULT;    switch(cmd) {      case SCULLV_IOCRESET:        scullv_qset = SCULLV_QSET;        scullv_order = SCULLV_ORDER;        break;              case SCULLV_IOCSORDER: /* Set: arg points to the value */        ret = __GET_USER(scullv_order, (int *) arg);        break;      case SCULLV_IOCTORDER: /* Tell: arg is the value */        scullv_order = arg;        break;      case SCULLV_IOCGORDER: /* Get: arg is pointer to result */        ret = __PUT_USER (scullv_order, (int *) arg);        break;      case SCULLV_IOCQORDER: /* Query: return it (it's positive) */        return scullv_order;      case SCULLV_IOCXORDER: /* eXchange: use arg as pointer */        tmp = scullv_order;        ret = __GET_USER(scullv_order, (int *) arg);        if (ret == 0)            ret = __PUT_USER(tmp, (int *) arg);        break;      case SCULLV_IOCHORDER: /* sHift: like Tell + Query */        tmp = scullv_order;        scullv_order = arg;        return tmp;              case SCULLV_IOCSQSET:        ret = __GET_USER(scullv_qset, (int *) arg);        break;      case SCULLV_IOCTQSET:        scullv_qset = arg;        break;      case SCULLV_IOCGQSET:        ret = __PUT_USER(scullv_qset, (int *)arg);        break;      case SCULLV_IOCQQSET:        return scullv_qset;      case SCULLV_IOCXQSET:        tmp = scullv_qset;        ret = __GET_USER(scullv_qset, (int *) arg);        if (ret == 0)            ret = __PUT_USER(tmp, (int *)arg);        break;      case SCULLV_IOCHQSET:        tmp = scullv_qset;        scullv_qset = arg;        return tmp;      default:  /* redundant, as cmd was checked against MAXNR */        return -ENOTTY;    }    return ret;}/* * The "extended" operations */loff_t scullv_llseek (struct file *filp, loff_t off, int whence){    ScullV_Dev *dev = filp->private_data;    long newpos;    switch(whence) {      case 0: /* SEEK_SET */        newpos = off;        break;      case 1: /* SEEK_CUR */        newpos = filp->f_pos + off;        break;      case 2: /* SEEK_END */        newpos = dev->size + off;        break;      default: /* can't happen */        return -EINVAL;    }    if (newpos<0) return -EINVAL;    filp->f_pos = newpos;    return newpos;} /* * Mmap *is* available, but confined in a different file */#ifndef LINUX_20extern int scullv_mmap(struct file *filp, struct vm_area_struct *vma);#elseextern int scullv_mmap(struct inode *inode, struct file *filp,		struct vm_area_struct *vma);#endif/* * The 2.0 wrappers */#ifdef LINUX_20int scullv_lseek_20 (struct inode *ino, struct file *f,                off_t offset, int whence){    return (int)scullv_llseek(f, offset, whence);}int scullv_read_20 (struct inode *ino, struct file *f, char *buf, int count){    return (int)scullv_read(f, buf, count, &f->f_pos);}int scullv_write_20 (struct inode *ino, struct file *f, const char *b, int c){    return (int)scullv_write(f, b, c, &f->f_pos);}void scullv_release_20 (struct inode *ino, struct file *f){    scullv_release(ino, f);}#define scullv_llseek scullv_lseek_20#define scullv_read scullv_read_20#define scullv_write scullv_write_20#define scullv_release scullv_release_20#define llseek lseek#endif /* LINUX_20 *//* * The fops */struct file_operations scullv_fops = {    llseek: scullv_llseek,    read: scullv_read,    write: scullv_write,    ioctl: scullv_ioctl,    mmap: scullv_mmap,    open: scullv_open,    release: scullv_release,};int scullv_trim(ScullV_Dev *dev){    ScullV_Dev *next, *dptr;    int qset = dev->qset;   /* "dev" is not-null */    int i;    if (dev->vmas) /* don't trim: there are active mappings */        return -EBUSY;    for (dptr = dev; dptr; dptr = next) { /* all the list items */        if (dptr->data) {            /* Release the quantum-set */            for (i = 0; i < qset; i++)                if (dptr->data[i])                    vfree(dptr->data[i]);            kfree(dptr->data);            dptr->data=NULL;        }        next=dptr->next;        if (dptr != dev) kfree(dptr); /* all of them but the first */    }    dev->size = 0;    dev->qset = scullv_qset;    dev->order = scullv_order;    dev->next = NULL;    return 0;}/* * Finally, the module stuff */int scullv_init(void){    int result, i;    SET_MODULE_OWNER(&scullv_fops);    /*     * Register your major, and accept a dynamic number     */    result = register_chrdev(scullv_major, "scullv", &scullv_fops);    if (result < 0) return result;    if (scullv_major == 0) scullv_major = result; /* dynamic */    /*      * allocate the devices -- we can't have them static, as the number     * can be specified at load time     */    scullv_devices = kmalloc(scullv_devs * sizeof (ScullV_Dev), GFP_KERNEL);    if (!scullv_devices) {        result = -ENOMEM;        goto fail_malloc;    }    memset(scullv_devices, 0, scullv_devs * sizeof (ScullV_Dev));    for (i=0; i < scullv_devs; i++) {        scullv_devices[i].order = scullv_order;        scullv_devices[i].qset = scullv_qset;        sema_init (&scullv_devices[i].sem, 1);    }#ifdef SCULLV_USE_PROC /* only when available */    create_proc_read_entry("scullvmem", 0, NULL, scullv_read_procmem, NULL);#endif    return 0; /* succeed */  fail_malloc:    unregister_chrdev(scullv_major, "scullv");    return result;}void scullv_cleanup(void){    int i;    unregister_chrdev(scullv_major, "scullv");#ifdef SCULLV_USE_PROC    remove_proc_entry("scullvmem", 0);#endif    for (i=0; i<scullv_devs; i++)        scullv_trim(scullv_devices+i);    kfree(scullv_devices);}module_init(scullv_init);module_exit(scullv_cleanup);