#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/device.h>
#include <linux/stat.h>

#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/workqueue.h>

#include <linux/io.h>
#include "gpioregs.h"

#define DEVICE_NAME "writeprotect"
#define CLASS_NAME "writeprotect_class"
#define BUFFER_SIZE 1024

// 可以通过模块参数指定主设备号和次设备号
static int writeprotect_major = 56; // 默认主设备号
static int writeprotect_minor = 90;   // 默认次设备号
module_param(writeprotect_major, int, S_IRUGO);
module_param(writeprotect_minor, int, S_IRUGO);
MODULE_PARM_DESC(writeprotect_major, "Major device number");
MODULE_PARM_DESC(writeprotect_minor, "Minor device number");

static struct class *char_class = NULL;
static struct device *char_device = NULL;
static struct cdev my_cdev;
static dev_t dev_num;

// 设备结构体
struct writeprotect_dev
{
    char *buffer;
    size_t size;
    struct mutex lock;
    struct cdev cdev;
    struct delayed_work delay_work1;
};

static struct writeprotect_dev *dev = NULL;

static void delay_work_func(struct work_struct *work)
{    
    printk(KERN_INFO "delay_work_func\n");
}

// 文件打开操作
static int writeprotect_open(struct inode *inode, struct file *filp)
{
    struct writeprotect_dev *dev;

    dev = container_of(inode->i_cdev, struct writeprotect_dev, cdev);
    filp->private_data = dev;

    printk(KERN_INFO "writeprotect: Device opened (major=%d, minor=%d)\n",
           imajor(inode), iminor(inode));
    return 0;
}

// 文件释放操作
static int writeprotect_release(struct inode *inode, struct file *filp)
{
    // release_region(PORT_80, 1);
    printk(KERN_INFO "writeprotect: Device closed\n");
    return 0;
}

// 读操作 - 支持cat命令
static ssize_t writeprotect_read(struct file *filp, char __user *buf,
                             size_t count, loff_t *f_pos)
{
    struct writeprotect_dev *dev = filp->private_data;
    ssize_t retval = 0;
    size_t available;
    int read_count = 0;
    int ret = 0;

    if (mutex_lock_interruptible(&dev->lock))
        return -ERESTARTSYS;

    // 这里read_count没有固定为4个字节，是为了便于后续扩展
    if (count > dev->size)
    {
        read_count = dev->size;
    }
    else
    {
        read_count = count;
    }
    ret = copy_to_user(buf, dev->buffer, read_count);
    if (ret != 0)
    {
        printk(KERN_INFO "writeprotect: copy_to_user failed\n");
        goto out;
    }

    printk(KERN_INFO "writeprotect: Read %zu bytes\n", count);

out:
    mutex_unlock(&dev->lock);
    return ret;
}

// 写操作
static ssize_t writeprotect_write(struct file *filp, const char __user *buf,
                              size_t count, loff_t *f_pos)
{
    struct writeprotect_dev *dev = filp->private_data;
    ssize_t retval = 0;
    size_t available;
    int ret = 0;

    // 加锁
    if (mutex_lock_interruptible(&dev->lock))
    {
        return -ERESTARTSYS;
    }

    // 计算可写数据量
    if (count > BUFFER_SIZE)
    {
        count = BUFFER_SIZE;
    }

    // 拷贝数据
    ret = copy_from_user(dev->buffer, buf, count);
    if (ret != 0)
    {
        printk(KERN_INFO "writeprotect: copy_from_user failed\n");
        goto out;
    }

    dev->size = count;

    printk(KERN_INFO "writeprotect: Written %zu bytes\n", count);

out:
    mutex_unlock(&dev->lock);

    // 调度延迟工作
    if (ret == 0)
    {
        schedule_delayed_work(&dev->delay_work1, msecs_to_jiffies(10));
    }
    return count;
}

// 文件操作结构体
static struct file_operations fops = {
    .owner = THIS_MODULE,
    .open = writeprotect_open,
    .release = writeprotect_release,
    .read = writeprotect_read,
    .write = writeprotect_write,
};

// 模块初始化
int writeprotect_init(void)
{
    int result;

    printk(KERN_INFO "writeprotect: Initializing driver with major=%d, minor=%d\n",
           writeprotect_major, writeprotect_minor);

    // 检查主设备号是否有效
    if (writeprotect_major <= 0)
    {
        printk(KERN_ALERT "writeprotect: Invalid major number %d\n", writeprotect_major);
        return -EINVAL;
    }

    // 构建设备号
    dev_num = MKDEV(writeprotect_major, writeprotect_minor);

    // 注册设备号 - 使用指定的主设备号
    result = register_chrdev_region(dev_num, 1, DEVICE_NAME);
    if (result < 0)
    {
        printk(KERN_ALERT "writeprotect: Failed to register major number %d\n", writeprotect_major);
        printk(KERN_ALERT "writeprotect: Try using a different major number\n");
        return result;
    }

    printk(KERN_INFO "writeprotect: Registered with major=%d, minor=%d\n",
           MAJOR(dev_num), MINOR(dev_num));

    // 分配设备结构体
    dev = kmalloc(sizeof(struct writeprotect_dev), GFP_KERNEL);
    if (!dev)
    {
        result = -ENOMEM;
        goto fail_malloc;
    }
    memset(dev, 0, sizeof(struct writeprotect_dev));

    // 分配缓冲区
    dev->buffer = kmalloc(BUFFER_SIZE, GFP_KERNEL);
    if (!dev->buffer)
    {
        result = -ENOMEM;
        goto fail_buffer;
    }

    // 初始化互斥锁
    mutex_init(&dev->lock);

    INIT_DELAYED_WORK(&dev->delay_work1, delay_work_func);

    // 初始化字符设备
    cdev_init(&dev->cdev, &fops);
    dev->cdev.owner = THIS_MODULE;

    // 添加字符设备到系统
    result = cdev_add(&dev->cdev, dev_num, 1);
    if (result)
    {
        printk(KERN_ALERT "writeprotect: Failed to add cdev\n");
        goto fail_cdev;
    }

    // 创建设备类
    char_class = class_create(THIS_MODULE, CLASS_NAME);
    if (IS_ERR(char_class))
    {
        result = PTR_ERR(char_class);
        printk(KERN_ALERT "writeprotect: Failed to create class\n");
        goto fail_class;
    }

    // 创建设备
    char_device = device_create(char_class, NULL, dev_num, NULL, DEVICE_NAME);
    if (IS_ERR(char_device))
    {
        result = PTR_ERR(char_device);
        printk(KERN_ALERT "writeprotect: Failed to create device\n");
        goto fail_device;
    }

    printk(KERN_INFO "writeprotect: Driver initialized successfully\n");
    printk(KERN_INFO "writeprotect: Device node: /dev/%s (major=%d, minor=%d)\n",
           DEVICE_NAME, writeprotect_major, writeprotect_minor);
    return 0;

fail_device:
    class_destroy(char_class);
fail_class:
    cdev_del(&dev->cdev);
fail_cdev:
    kfree(dev->buffer);
fail_buffer:
    kfree(dev);
fail_malloc:
    unregister_chrdev_region(dev_num, 1);
    return result;
}

// 模块退出
void writeprotect_exit(void)
{
    cancel_delayed_work_sync(&dev->delay_work1);
    device_destroy(char_class, dev_num);
    class_destroy(char_class);

    if (dev)
    {
        cdev_del(&dev->cdev);
        if (dev->buffer)
            kfree(dev->buffer);
        kfree(dev);
    }

    unregister_chrdev_region(dev_num, 1);
    printk(KERN_INFO "writeprotect: Driver removed (major=%d, minor=%d)\n",
           writeprotect_major, writeprotect_minor);
}