#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/i2c.h>
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/pci.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/string.h>

#define DRIVER_NAME "lcd2002"
#define LCD_I2C_ADDR_DEFAULT 0x3E

/* 控制字节定义 */
#define LCD_CONTROL_BYTE    0x00
#define LCD_DATA_BYTE       0x40

/* 基本指令 */
#define LCD_CLEAR_DISPLAY   0x01
#define LCD_RETURN_HOME     0x02
#define LCD_ENTRY_MODE_SET  0x04
#define LCD_DISPLAY_CONTROL 0x08
#define LCD_CURSOR_SHIFT    0x10
#define LCD_FUNCTION_SET    0x20
#define LCD_SET_CGRAM_ADDR  0x40
#define LCD_SET_DDRAM_ADDR  0x80

/* Entry Mode */
#define LCD_ENTRY_RIGHT     0x00
#define LCD_ENTRY_LEFT      0x02

/* Display Control */
#define LCD_DISPLAY_ON      0x04
#define LCD_DISPLAY_OFF     0x00
#define LCD_CURSOR_ON       0x02
#define LCD_CURSOR_OFF      0x00
#define LCD_BLINK_ON        0x01
#define LCD_BLINK_OFF       0x00

#define LCD_LINE1_ADDR      0x00
#define LCD_LINE2_ADDR      0x40
#define LCD_COLS            20
#define LCD_ROWS            2

/* IOCTL */
#define LCD_IOCTL_MAGIC     'L'
#define LCD_IOCTL_CLEAR     _IO(LCD_IOCTL_MAGIC, 0)
#define LCD_IOCTL_HOME      _IO(LCD_IOCTL_MAGIC, 1)
#define LCD_IOCTL_SET_CURSOR _IOW(LCD_IOCTL_MAGIC, 2, struct lcd_pos)
#define LCD_IOCTL_DISPLAY_CTRL _IOW(LCD_IOCTL_MAGIC, 3, unsigned char[3])

struct lcd_pos {
    unsigned char col;
    unsigned char row;
};

struct lcd2002_dev {
    struct i2c_adapter *adapter;
    struct mutex lock;
    unsigned char addr;
};

static struct lcd2002_dev *lcd_dev = NULL;

/* 模块参数 - 多种匹配方式 */
static char *pci_addr = "0000:00:15.0";
module_param(pci_addr, charp, 0444);
MODULE_PARM_DESC(pci_addr, "PCI address (e.g., 0000:00:15.0)");

static char *adapter_name = NULL;  /* 如: "Synopsys DesignWare I2C adapter" */
module_param(adapter_name, charp, 0444);
MODULE_PARM_DESC(adapter_name, "I2C adapter name (e.g., Synopsys DesignWare)");

static int i2c_bus = -1;  /* 直接指定总线号，如 1 对应 /dev/i2c-1 */
module_param(i2c_bus, int, 0444);
MODULE_PARM_DESC(i2c_bus, "I2C bus number (e.g., 1 for /dev/i2c-1)");

static unsigned char i2c_address = LCD_I2C_ADDR_DEFAULT;
module_param(i2c_address, byte, 0444);
MODULE_PARM_DESC(i2c_address, "LCD I2C address (default: 0x3E)");

static int debug = 1;
module_param(debug, int, 0644);
MODULE_PARM_DESC(debug, "Debug level (0=none, 1=normal, 2=verbose)");

/* 延时 */
static inline void lcd_delay_ms(unsigned int ms)
{
    msleep(ms);
}

/* I2C写 */
static int lcd_i2c_write(unsigned char *buf, int len)
{
    struct i2c_msg msg;
    int ret;

    if (!lcd_dev || !lcd_dev->adapter)
        return -ENODEV;

    msg.addr = lcd_dev->addr;
    msg.flags = 0;
    msg.len = len;
    msg.buf = buf;

    ret = i2c_transfer(lcd_dev->adapter, &msg, 1);
    if (ret != 1) {
        dev_err(&lcd_dev->adapter->dev, "I2C write failed: %d\n", ret);
        return ret < 0 ? ret : -EIO;
    }
    return 0;
}

/* 发送指令 */
static int lcd_send_command(unsigned char cmd)
{
    unsigned char buf[2];
    int ret;

    buf[0] = LCD_CONTROL_BYTE;
    buf[1] = cmd;

    mutex_lock(&lcd_dev->lock);
    ret = lcd_i2c_write(buf, 2);
    mutex_unlock(&lcd_dev->lock);

    if (ret == 0)
        lcd_delay_ms(2);
    return ret;
}

/* 发送数据 */
static int lcd_send_data(unsigned char data)
{
    unsigned char buf[2];
    int ret;

    buf[0] = LCD_DATA_BYTE;
    buf[1] = data;

    mutex_lock(&lcd_dev->lock);
    ret = lcd_i2c_write(buf, 2);
    mutex_unlock(&lcd_dev->lock);

    if (ret == 0)
        lcd_delay_ms(1);
    return ret;
}

/* 初始化LCD */
static int lcd_init_display(void)
{
    int ret;

    lcd_delay_ms(50);

    /* 功能设置: 2行, 5x8点阵 (0x28) */
    ret = lcd_send_command(LCD_FUNCTION_SET | 0x08);
    if (ret < 0) return ret;
    lcd_delay_ms(5);

    /* 显示开,光标关,闪烁关 (0x0C) */
    ret = lcd_send_command(LCD_DISPLAY_CONTROL | LCD_DISPLAY_ON | LCD_CURSOR_OFF | LCD_BLINK_OFF);
    if (ret < 0) return ret;

    /* 清屏 */
    ret = lcd_send_command(LCD_CLEAR_DISPLAY);
    if (ret < 0) return ret;
    lcd_delay_ms(3);

    /* 输入模式: 光标右移 (0x06) */
    ret = lcd_send_command(LCD_ENTRY_MODE_SET | LCD_ENTRY_RIGHT);
    
    return ret;
}

/* 设置光标 */
static int lcd_set_cursor(unsigned char col, unsigned char row)
{
    unsigned char addr;
    if (col >= LCD_COLS || row >= LCD_ROWS)
        return -EINVAL;
    addr = (row == 0) ? (LCD_LINE1_ADDR + col) : (LCD_LINE2_ADDR + col);
    return lcd_send_command(LCD_SET_DDRAM_ADDR | addr);
}

/* 清屏 */
static int lcd_clear(void)
{
    int ret = lcd_send_command(LCD_CLEAR_DISPLAY);
    if (ret == 0) lcd_delay_ms(2);
    return ret;
}

/* 显示控制 */
static int lcd_display_control(unsigned char display, unsigned char cursor, unsigned char blink)
{
    return lcd_send_command(LCD_DISPLAY_CONTROL | display | cursor | blink);
}

/* 写字符串 */
static int lcd_write_string(const char *str, size_t len)
{
    size_t i;
    int ret = 0;
    unsigned char row = 0, col = 0;

    for (i = 0; i < len; i++) {
        char c = str[i];
        if (c == '\n') {
            row = (row + 1) % LCD_ROWS;
            col = 0;
            ret = lcd_set_cursor(col, row);
        } else if (c == '\r') {
            col = 0;
            ret = lcd_set_cursor(col, row);
        } else if (c == '\f') {
            ret = lcd_clear();
            row = col = 0;
        } else {
            if (col >= LCD_COLS) {
                row = (row + 1) % LCD_ROWS;
                col = 0;
                ret = lcd_set_cursor(col, row);
                if (ret < 0) break;
            }
            ret = lcd_send_data(c);
            col++;
        }
        if (ret < 0) break;
    }
    return ret;
}

/* 调试：打印适配器信息 */
static void print_adapter_info(struct i2c_adapter *adap, int nr)
{
    struct device *parent;
    char pci_str[64] = "N/A";
    
    if (!debug) return;
    
    pr_info("  [%d] %s (class: 0x%lx)\n", nr, adap->name, adap->class);
    
    parent = adap->dev.parent;
    while (parent) {
        if (parent->bus == &pci_bus_type) {
            struct pci_dev *pdev = to_pci_dev(parent);
            snprintf(pci_str, sizeof(pci_str), "%04x:%02x:%02x.%x",
                pci_domain_nr(pdev->bus),
                pdev->bus->number,
                PCI_SLOT(pdev->devfn),
                PCI_FUNC(pdev->devfn));
            pr_info("      -> PCI: %s [%s]\n", pci_str, dev_name(parent));
            break;
        } else {
            pr_info("      -> %s [%s]\n", dev_name(parent), parent->bus ? parent->bus->name : "no-bus");
        }
        parent = parent->parent;
    }
}

/* 方式1: 通过PCI地址查找 */
static struct i2c_adapter *find_by_pci(const char *target_pci)
{
    struct i2c_adapter *adapter;
    int nr = 0;
    bool found = false;
    
    pr_info("Searching for PCI %s...\n", target_pci);
    
    while ((adapter = i2c_get_adapter(nr))) {
        struct device *parent = adapter->dev.parent;
        char pci_buf[32] = "";
        
        if (debug >= 2)
            print_adapter_info(adapter, nr);
        
        /* 递归向上查找PCI设备 */
        while (parent && !found) {
            if (parent->bus == &pci_bus_type) {
                struct pci_dev *pdev = to_pci_dev(parent);
                snprintf(pci_buf, sizeof(pci_buf), "%04x:%02x:%02x.%x",
                    pci_domain_nr(pdev->bus),
                    pdev->bus->number,
                    PCI_SLOT(pdev->devfn),
                    PCI_FUNC(pdev->devfn));
                
                if (strcmp(pci_buf, target_pci) == 0) {
                    pr_info("Found match at i2c-%d: %s\n", nr, adapter->name);
                    found = true;
                    break;
                }
                break; /* 只检查第一级PCI父设备 */
            }
            parent = parent->parent;
        }
        
        if (found)
            return adapter;
            
        i2c_put_adapter(adapter);
        nr++;
    }
    
    return NULL;
}

/* 方式2: 通过名称查找 */
static struct i2c_adapter *find_by_name(const char *name)
{
    struct i2c_adapter *adapter;
    int nr = 0;
    
    pr_info("Searching for adapter name '%s'...\n", name);
    
    while ((adapter = i2c_get_adapter(nr))) {
        if (debug >= 2)
            print_adapter_info(adapter, nr);
            
        if (strstr(adapter->name, name)) {
            pr_info("Found match at i2c-%d: %s\n", nr, adapter->name);
            return adapter;
        }
        i2c_put_adapter(adapter);
        nr++;
    }
    
    return NULL;
}

/* 方式3: 通过总线号 */
static struct i2c_adapter *find_by_bus(int bus)
{
    pr_info("Trying i2c bus %d...\n", bus);
    return i2c_get_adapter(bus);
}

/* 查找适配器主函数 */
static struct i2c_adapter *find_adapter(void)
{
    struct i2c_adapter *adapter = NULL;
    
    /* 优先级1: 直接指定总线号 */
    if (i2c_bus >= 0) {
        adapter = find_by_bus(i2c_bus);
        if (adapter) goto done;
        pr_warn("Specified i2c_bus %d not found\n", i2c_bus);
    }
    
    /* 优先级2: PCI地址 */
    if (pci_addr && strlen(pci_addr) > 0) {
        adapter = find_by_pci(pci_addr);
        if (adapter) goto done;
        pr_warn("PCI address %s not found\n", pci_addr);
    }
    
    /* 优先级3: 适配器名称 */
    if (adapter_name && strlen(adapter_name) > 0) {
        adapter = find_by_name(adapter_name);
        if (adapter) goto done;
        pr_warn("Adapter name '%s' not found\n", adapter_name);
    }
    
    /* 回退: 自动检测常见名称 (Synopsys DesignWare) */
    pr_info("Trying auto-detect (Synopsys DesignWare)...\n");
    adapter = find_by_name("Synopsys DesignWare");
    if (adapter) goto done;
    
    /* 最后回退: 使用 i2c-1 (根据用户环境) */
    pr_info("Trying fallback i2c-1...\n");
    adapter = find_by_bus(1);
    
done:
    return adapter;
}

/* 文件操作 */
static int lcd_open(struct inode *inode, struct file *file)
{
    return lcd_dev ? 0 : -ENODEV;
}

static int lcd_release(struct inode *inode, struct file *file)
{
    return 0;
}

static ssize_t lcd_write(struct file *file, const char __user *buf, 
                        size_t count, loff_t *ppos)
{
    char *kbuf;
    int ret;
    
    if (count == 0) return 0;
    if (count > 256) count = 256;
        
    kbuf = kmalloc(count + 1, GFP_KERNEL);
    if (!kbuf) return -ENOMEM;
        
    if (copy_from_user(kbuf, buf, count)) {
        kfree(kbuf);
        return -EFAULT;
    }
    kbuf[count] = '\0';
    
    ret = lcd_write_string(kbuf, count);
    kfree(kbuf);
    
    return ret < 0 ? ret : count;
}

static long lcd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    int ret = 0;
    
    switch (cmd) {
    case LCD_IOCTL_CLEAR:
        ret = lcd_clear();
        break;
    case LCD_IOCTL_HOME:
        ret = lcd_send_command(LCD_RETURN_HOME);
        if (ret == 0) lcd_delay_ms(2);
        break;
    case LCD_IOCTL_SET_CURSOR: {
        struct lcd_pos pos;
        if (copy_from_user(&pos, (void __user *)arg, sizeof(pos)))
            return -EFAULT;
        ret = lcd_set_cursor(pos.col, pos.row);
        break;
    }
    case LCD_IOCTL_DISPLAY_CTRL: {
        unsigned char ctrl[3];
        if (copy_from_user(ctrl, (void __user *)arg, sizeof(ctrl)))
            return -EFAULT;
        ret = lcd_display_control(ctrl[0], ctrl[1], ctrl[2]);
        break;
    }
    default:
        ret = -EINVAL;
    }
    return ret;
}

static const struct file_operations lcd_fops = {
    .owner = THIS_MODULE,
    .open = lcd_open,
    .release = lcd_release,
    .write = lcd_write,
    .unlocked_ioctl = lcd_ioctl,
    .compat_ioctl = lcd_ioctl,
};

static struct miscdevice lcd_miscdev = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = "lcd2002",
    .fops = &lcd_fops,
    .mode = 0666,
};

int lcd2x20_init(void)
{
    int ret;
    
    pr_info("LCD2002 driver loading (PCI:%s, Bus:%d, Addr:0x%02X)...\n",
            pci_addr ? pci_addr : "none", i2c_bus, i2c_address);
    
    lcd_dev = kzalloc(sizeof(*lcd_dev), GFP_KERNEL);
    if (!lcd_dev)
        return -ENOMEM;
        
    mutex_init(&lcd_dev->lock);
    lcd_dev->addr = i2c_address;
    
    /* 查找适配器 */
    lcd_dev->adapter = find_adapter();
    if (!lcd_dev->adapter) {
        pr_err("Failed to find any suitable I2C adapter!\n");
        pr_err("Available adapters (from i2cdetect -l):\n");
        {
            int nr = 0;
            struct i2c_adapter *a;
            while ((a = i2c_get_adapter(nr++))) {
                pr_err("  i2c-%d: %s\n", nr-1, a->name);
                i2c_put_adapter(a);
            }
        }
        ret = -ENODEV;
        goto err_free;
    }
    
    pr_info("Using I2C adapter: %s\n", lcd_dev->adapter->name);
    
    /* 初始化LCD */
    ret = lcd_init_display();
    if (ret < 0) {
        pr_err("LCD init failed: %d\n", ret);
        goto err_put;
    }
    
    ret = misc_register(&lcd_miscdev);
    if (ret < 0) {
        pr_err("Misc register failed: %d\n", ret);
        goto err_put;
    }
    
    pr_info("LCD2002 ready at /dev/%s\n", lcd_miscdev.name);
    
    /* 欢迎信息 */
    lcd_clear();
    lcd_write_string("LCD2002 Driver OK", 17);
    lcd_set_cursor(0, 1);
    lcd_write_string("Intel ADL-N97", 13);
    
    return 0;

err_put:
    i2c_put_adapter(lcd_dev->adapter);
err_free:
    kfree(lcd_dev);
    lcd_dev = NULL;
    return ret;
}

void lcd2x20_exit(void)
{
    if (!lcd_dev) return;
    
    misc_deregister(&lcd_miscdev);
    lcd_send_command(LCD_DISPLAY_CONTROL | LCD_DISPLAY_OFF);
    
    if (lcd_dev->adapter)
        i2c_put_adapter(lcd_dev->adapter);
        
    kfree(lcd_dev);
    lcd_dev = NULL;
    pr_info("LCD2002 driver unloaded\n");
}