mmap方法

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/cdev.h>
#include <linux/mm.h>
#include <linux/kdev_t.h>

#define DEVICE "sky"

struct sky_struct
{
        dev_t devno;
        struct cdev cdev;
};

struct sky_struct sky;

static void vm_ops_open(struct vm_area_struct *area)
{
        printk(KERN_ALERT "vm_ops_open/n");
}

static void vm_ops_close(struct vm_area_struct *area)
{
        printk(KERN_ALERT "vm_ops_close/n");
}

static struct vm_operations_struct vm_ops =
{
        .open = vm_ops_open,
        .close = vm_ops_close,
};

static int sky_mmap(struct file *filp, struct vm_area_struct *vm)
{
        unsigned long start, end, size, pfn;
        pgprot_t prot;

        start = vm->vm_start;
        end = vm->vm_end;
        size = end - start;
        pfn = vm->vm_pgoff;
        prot = vm->vm_page_prot;

        if (remap_pfn_range(vm, start, pfn, size, prot) < 0)
        {
                goto remap_err;
        }

        vm->vm_ops = &vm_ops;
        vm_ops_open(vm);

        return 0;
remap_err:
        return -1;
}

static struct file_operations fops =
{
        .mmap = sky_mmap,
};

static int __init sky_init(void)
{
        if (alloc_chrdev_region(&sky.devno, 0, 1, DEVICE) < 0)
        {
                goto alloc_err;
        }

        cdev_init(&sky.cdev, &fops);
        sky.cdev.owner = THIS_MODULE;
        sky.cdev.ops = &fops;
        if (cdev_add(&sky.cdev, sky.devno, 1) < 0)
        {
                goto add_err;
        }

        return 0;
add_err:
        unregister_chrdev_region(sky.devno, 1);
alloc_err:
        return -1;
}

static void __exit sky_exit(void)
{
        cdev_del(&sky.cdev);
        unregister_chrdev_region(sky.devno, 1);
}

MODULE_LICENSE("GPL");

module_init(sky_init);
module_exit(sky_exit);