linux 驱动 mmap

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/mm.h>

static int major_number;
static char *device_buffer;

static int my_mmap(struct file *file, struct vm_area_struct *vma) {
    unsigned long size = vma->vm_end - vma->vm_start;
    if (size > PAGE_SIZE) {
        return -EINVAL;
    }
    if (remap_pfn_range(vma, vma->vm_start,
                        virt_to_phys(device_buffer) >> PAGE_SHIFT,
                        size, vma->vm_page_prot)) {
        return -EAGAIN;
    }
    return 0;
}

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

static int __init my_init(void) {
    major_number = register_chrdev(0, "my_device", &fops);
    if (major_number < 0) {
        printk(KERN_ALERT "Failed to register device\n");
        return major_number;
    }
    device_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
    if (!device_buffer) {
        unregister_chrdev(major_number, "my_device");
        printk(KERN_ALERT "Failed to allocate memory\n");
        return -ENOMEM;
    }
    printk(KERN_INFO "Device registered with major number %d\n", major_number);
    return 0;
}

static void __exit my_exit(void) {
    kfree(device_buffer);
    unregister_chrdev(major_number, "my_device");
    printk(KERN_INFO "Device unregistered\n");
}

module_init(my_init);
module_exit(my_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("A simple mmap example");