#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 "buzzer"
#define CLASS_NAME "buzzer_class"
#define DRIVER_NAME     "buzzer_driver"
#define BUFFER_SIZE 1024

#define note(x) ((119318200+(x)/2)/(x))

// You can specify the major device number and minor device number through module parameters
static int buzzer_major = 56; // Default main device number
static int buzzer_minor = 100;   // Default sub-device number
module_param(buzzer_major, int, S_IRUGO);
module_param(buzzer_minor, int, S_IRUGO);
MODULE_PARM_DESC(buzzer_major, "Major device number");
MODULE_PARM_DESC(buzzer_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;


struct buzzer_dev
{
    char *buffer;
    size_t size;
    struct mutex lock;
    struct cdev cdev;
    struct delayed_work delay_work1;
};

static struct buzzer_dev *dev = NULL;

void IoWrite8 (uint16_t addr, uint8_t data)
{
    outb(data,addr);
}

uint8_t IoRead8 (uint16_t addr)
{
    return inb(addr);
}

void BeepOff(void)
{
	IoWrite8(BUZZER_PORT, IoRead8(BUZZER_PORT) & 0xfc);
}

void BeepOn(uint16_t freq)
{
	uint16_t Frequency = note(freq);
	//set up channel 1 (used for delays)
	IoWrite8(BUZZER_CHANNEL, 0x54);
	IoWrite8(BUZZER_CHAN_1, 0x12);
	//set up channel 2 (used by speaker)
	IoWrite8(BUZZER_CHANNEL, 0xb6);
	IoWrite8(BUZZER_FREQ, (uint8_t)Frequency);
	IoWrite8(BUZZER_FREQ, (uint8_t)(Frequency >> 8));
	//turn the speaker on
	IoWrite8(BUZZER_PORT, IoRead8(BUZZER_PORT) | 3);
}
static void delay_work_func(struct work_struct *work)
{
    int status_flag = 0;
    int freq = 0;
    int duration = 0;
    if(dev->size < 4)
    {
        printk(KERN_INFO "buzzer: size < 4\n");
        return;
    }
    // Close buzzer
    BeepOff();
    printk(KERN_INFO "delay_work_func\n");
}

static int buzzer_open(struct inode *inode, struct file *filp)
{
    struct buzzer_dev *dev;

    // if (!request_region(PORT_80, 1, DRIVER_NAME))
    // {
    //     pr_err("Port 80 I/O region busy\n");
    //     return -EBUSY;
    // }

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

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

static int buzzer_release(struct inode *inode, struct file *filp)
{
    // release_region(PORT_80, 1);
    printk(KERN_INFO "buzzer: Device closed\n");
    return 0;
}

static ssize_t buzzer_read(struct file *filp, char __user *buf,
                             size_t count, loff_t *f_pos)
{
    struct buzzer_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;

    // The read count here is not fixed at 4 bytes, in order to facilitate future expansion.
    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 "buzzer: copy_to_user failed\n");
        goto out;
    }

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

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

static ssize_t buzzer_write(struct file *filp, const char __user *buf,
                              size_t count, loff_t *f_pos)
{
    struct buzzer_dev *dev = filp->private_data;
    ssize_t retval = 0;
    size_t available;
    int ret = 0;
    int status_flag = 0;
    int freq = 0;
    int duration = 0;    

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

    if (count > BUFFER_SIZE)
    {
        count = BUFFER_SIZE;
    }

    if(count < 4)
    {
        printk(KERN_INFO "buzzer: count < 4\n");
        ret = -1;
        goto out;
    }

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

    dev->size = count;

    status_flag = dev->buffer[0];
    freq = dev->buffer[2]<<8 + dev->buffer[1];
    duration = dev->buffer[3];

    if(status_flag == 1)
    {
        BeepOn(freq);
    }
    else
    {
        BeepOff();
    }

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

out:
    mutex_unlock(&dev->lock);

    if (ret == 0)
    {
        schedule_delayed_work(&dev->delay_work1, msecs_to_jiffies(duration*1000));
    }
    return count;
}

static struct file_operations fops = {
    .owner = THIS_MODULE,
    .open = buzzer_open,
    .release = buzzer_release,
    .read = buzzer_read,
    .write = buzzer_write,
};

int buzzer_init(void)
{
    int result;

    printk(KERN_INFO "buzzer: Initializing driver with major=%d, minor=%d\n",
           buzzer_major, buzzer_minor);

    if (buzzer_major <= 0)
    {
        printk(KERN_ALERT "buzzer: Invalid major number %d\n", buzzer_major);
        return -EINVAL;
    }

    dev_num = MKDEV(buzzer_major, buzzer_minor);

    result = register_chrdev_region(dev_num, 1, DEVICE_NAME);
    if (result < 0)
    {
        printk(KERN_ALERT "buzzer: Failed to register major number %d\n", buzzer_major);
        printk(KERN_ALERT "buzzer: Try using a different major number\n");
        return result;
    }

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

    dev = kmalloc(sizeof(struct buzzer_dev), GFP_KERNEL);
    if (!dev)
    {
        result = -ENOMEM;
        goto fail_malloc;
    }
    memset(dev, 0, sizeof(struct buzzer_dev));

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

    mutex_init(&dev->lock);

    INIT_DELAYED_WORK(&dev->delay_work1, delay_work_func);

    cdev_init(&dev->cdev, &fops);
    dev->cdev.owner = THIS_MODULE;

    result = cdev_add(&dev->cdev, dev_num, 1);
    if (result)
    {
        printk(KERN_ALERT "buzzer: Failed to add cdev\n");
        goto fail_cdev;
    }

    char_class = class_create(THIS_MODULE, CLASS_NAME);
    if (IS_ERR(char_class))
    {
        result = PTR_ERR(char_class);
        printk(KERN_ALERT "buzzer: Failed to create class\n");
        goto fail_class;
    }

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

    printk(KERN_INFO "buzzer: Driver initialized successfully\n");
    printk(KERN_INFO "buzzer: Device node: /dev/%s (major=%d, minor=%d)\n",
           DEVICE_NAME, buzzer_major, buzzer_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;
}

void buzzer_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 "buzzer: Driver removed (major=%d, minor=%d)\n",
           buzzer_major, buzzer_minor);
}