#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 "myname"
#define CLASS_NAME "myname_class"
#define BUFFER_SIZE 1024


#define SWITCH_ID0 0xFD6D0A40
#define SWITCH_ID1 0xFD6D0A50
#define SWITCH_ID2 0xFD6D0B20
#define SWITCH_ID3 0xFD6D0B30
#define SWITCH_ID4 0xFD6D0B40

// 可以通过模块参数指定主设备号和次设备号
static int myname_major = 56; // 默认主设备号
static int myname_minor = 130;   // 默认次设备号
module_param(myname_major, int, S_IRUGO);
module_param(myname_minor, int, S_IRUGO);
MODULE_PARM_DESC(myname_major, "Major device number");
MODULE_PARM_DESC(myname_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 myname_dev
{
    char *buffer;
    size_t size;
    struct mutex lock;
    struct cdev cdev;
    struct delayed_work delay_work1;
    int board_id;
};

static struct myname_dev *dev = NULL;

unsigned int myname_readl(unsigned int addr)
{
    void __iomem *reg_base = NULL;
    reg_base = ioremap(addr, 0x1000);
    return readl(reg_base);
}

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

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

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

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

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

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

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

    // 关键检查：是否已经读到文件末尾？
    if (*f_pos >= dev->size) {
        printk(KERN_DEBUG "myname: EOF reached (pos=%lld, size=%zu)\n", 
               *f_pos, dev->size);
        mutex_unlock(&dev->lock);
        return 0;  // 返回 0 告诉 cat 文件结束
    }

    // 计算剩余可读字节数
    size_t available = dev->size - *f_pos;
    
    // 确定本次读取的字节数
    if (count > available) {
        retval = available;
    } else {
        retval = count;
    }

    printk(KERN_DEBUG "myname: Attempting to read %zu bytes from pos %lld\n", 
           retval, *f_pos);

    ret = copy_to_user(buf, dev->buffer + *f_pos, retval);
    if (ret != 0) {
        printk(KERN_ERR "myname: copy_to_user failed\n");
        mutex_unlock(&dev->lock);
        return -EFAULT;
    }

    // 更新文件位置指针 - 这一步非常关键！
    *f_pos += retval;

    printk(KERN_DEBUG "myname: Read %zu bytes, new pos=%lld\n", retval, *f_pos);

    mutex_unlock(&dev->lock);
    return retval;  // 返回实际读取的字节数
}

// 写操作
static ssize_t myname_write(struct file *filp, const char __user *buf,
                              size_t count, loff_t *f_pos)
{
    struct myname_dev *dev = filp->private_data;
    ssize_t retval = 0;
    size_t available;
    int ret = 0;
    return -1;

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

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

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

    dev->size = count;

    printk(KERN_ERR "myname: 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 = myname_open,
    .release = myname_release,
    .read = myname_read,
    .write = myname_write,
};

// 获取board_id
int get_board_id(void)
{
    unsigned int board_id = 0;

    board_id |= (myname_readl(SWITCH_ID0)&0x02) >> 1;
    board_id |= myname_readl(SWITCH_ID1)&0x02;
    board_id |= (myname_readl(SWITCH_ID2)&0x02) << 1;
    board_id |= (myname_readl(SWITCH_ID3)%0x02) << 2;
    board_id |= (myname_readl(SWITCH_ID4)%0x02) << 3;
    printk("board_id=%08x\n", board_id);

    if(board_id > 15)
    {
        printk(KERN_ERR "myname: Invalid board_id\n");
        return -EINVAL;
    }
    if(board_id == 0)
    {
        memcpy(dev->buffer, "ci (Ruby Ci)", strlen("ci (Ruby Ci)"));
        dev->size = strlen("ci (Ruby Ci)");
    }
    else if(board_id >= 1 && board_id <= 7)
    {
        memcpy(dev->buffer, "python (c18)", strlen("python (c18)"));
        dev->size = strlen("python (c18)");
    }
    else if(board_id >= 8 && board_id <= 11)
    {
        memcpy(dev->buffer, "selene", strlen("selene"));
        dev->size = strlen("selene");
    }
    else if(board_id >= 12 && board_id <= 15)
    {
        memcpy(dev->buffer, "cobra (Commander Ci)", strlen("cobra (Commander Ci)"));
        dev->size = strlen("cobra (Commander Ci)");
    }
    printk(KERN_ERR "myname: board_id = %d\n", board_id);
    return board_id;
}

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

    printk(KERN_ERR "myname: Initializing driver with major=%d, minor=%d\n",
           myname_major, myname_minor);

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

    // 构建设备号
    dev_num = MKDEV(myname_major, myname_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 "myname: Failed to register major number %d\n", myname_major);
        printk(KERN_ALERT "myname: Try using a different major number\n");
        return result;
    }

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

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

    // 分配缓冲区
    dev->buffer = kmalloc(BUFFER_SIZE, GFP_KERNEL);
    if (!dev->buffer)
    {
        result = -ENOMEM;
        goto fail_buffer;
    }
    memset(dev->buffer, 0, BUFFER_SIZE);
    // 初始化互斥锁
    mutex_init(&dev->lock);

    INIT_DELAYED_WORK(&dev->delay_work1, delay_work_func);
    dev->board_id = get_board_id();
    printk(KERN_ERR "myname: %s\n", dev->buffer);

    // 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 "myname: 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 "myname: 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 "myname: Failed to create device\n");
        goto fail_device;
    }

    printk(KERN_ERR "myname: Driver initialized successfully\n");
    printk(KERN_ERR "myname: Device node: /dev/%s (major=%d, minor=%d)\n",
           DEVICE_NAME, myname_major, myname_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 myname_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_ERR "myname: Driver removed (major=%d, minor=%d)\n",
           myname_major, myname_minor);
}