reserve_virt_addr = ioremap(mem_start *1024 * 1024, mem_size *1024 * 1024);
　printk("reserve_virt_addr = 0x%lx\n", (unsigned long)reserve_virt_addr);
　if (reserve_virt_addr)
　{
　　int i;
　　for (i = 0; i < mem_size *1024 * 1024; i += 4)
　　{
　　　reserve_virt_addr[i] = 'a';
　　　reserve_virt_addr[i + 1] = 'b';
　　　reserve_virt_addr[i + 2] = 'c';
　　　reserve_virt_addr[i + 3] = 'd';
　　}
　}
　else
　{
　　unregister_chrdev(major, "mmapdrv");
　　return - ENODEV;
　}
　return 0;
}

/* remove the module */
void cleanup_module(void)
{
　if (reserve_virt_addr)
　　iounmap(reserve_virt_addr);

　unregister_chrdev(major, "mmapdrv");
　return ;
}

int mmapdrv_open(struct inode *inode, struct file *file)
{
　MOD_INC_USE_COUNT;
　return (0);
}

int mmapdrv_release(struct inode *inode, struct file *file)
{
　MOD_DEC_USE_COUNT;
　return (0);
}

int mmapdrv_mmap(struct file *file, struct vm_area_struct *vma)
{
　unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
　unsigned long size = vma->vm_end - vma->vm_start;

　if (size > mem_size *1024 * 1024)
　{
　　printk("size too big\n");
　　return ( - ENXIO);
　}

　offset = offset + mem_start * 1024 * 1024;

　/* we do not want to have this area swapped out, lock it */
　vma->vm_flags |= VM_LOCKED;
　if (remap_page_range(vma, vma->vm_start, offset, size, PAGE_SHARED))
　{
　　printk("remap page range failed\n");
　　return - ENXIO;
　}
　return (0);
}