#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/poll.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <asm/irq.h>
#include <mach/regs-gpio.h>
#include <mach/hardware.h>
#include <linux/miscdevice.h>

#define DEVICE_NAME         "button"    //設備名稱
               
#define KEY_TIMER_DELAY1    (HZ/50)             //按鍵按下去抖延時20毫秒        
#define KEY_TIMER_DELAY2    (HZ/10)             //按鍵抬起去抖延時100毫秒
#define KEY_DOWN            0                   //按鍵按下                    
#define KEY_UP              1                   //按鍵抬起                
#define KEY_UNCERTAIN       2                   //按鍵不確定    

#define KEY_COUNT           6                   //6個按鍵                    

static volatile int ev_press = 0;                //按鍵按下產生標志
static volatile int key_status[KEY_COUNT];       //記錄6個按鍵的狀態    
static struct timer_list key_timers[KEY_COUNT];  //定義6個按鍵去抖動定時器
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);    //定義并初始化等待隊列

//組織硬件資源結構體
struct button_irq_desc    
{
    int irq;            //中斷號
    int pin;            //引腳
    int pin_setting;    //引腳配置
    char *name;         //按鍵名稱，注意這個名稱，在后面的一個現象中會出現
};

//定義6個按鍵資源結構體數組
static struct button_irq_desc button_irqs[] =
 {
    {IRQ_EINT8 , S3C2410_GPG0 , S3C2410_GPG0_EINT8 , "KEY0"},
    {IRQ_EINT11, S3C2410_GPG3 , S3C2410_GPG3_EINT11 , "KEY1"},
    {IRQ_EINT13, S3C2410_GPG5 , S3C2410_GPG5_EINT13 , "KEY2"},
    {IRQ_EINT14, S3C2410_GPG6 , S3C2410_GPG6_EINT14 , "KEY3"},
    {IRQ_EINT15, S3C2410_GPG7 , S3C2410_GPG7_EINT15 , "KEY4"},
    {IRQ_EINT19, S3C2410_GPG11, S3C2410_GPG11_EINT19, "KEY5"},
};

static irqreturn_t buttons_interrupt(int irq, void *dev_id)
{
 //獲取當前按鍵資源的索引
    int key = (int)dev_id;

    if(key_status[key] == KEY_UP)
    {
        //設置當前按鍵的狀態為不確定
        key_status[key] = KEY_UNCERTAIN;

        //設置當前按鍵按下去抖定時器的延時并啟動定時器
        key_timers[key].expires = jiffies + KEY_TIMER_DELAY1;
        add_timer(&key_timers[key]);
    }

    return IRQ_RETVAL(IRQ_HANDLED);
}

static void buttons_timer(unsigned long arg)
{
    //獲取當前按鍵資源的索引
    int key = arg;

    //獲取當前按鍵引腳上的電平值來判斷按鍵是按下還是抬起
    int up = s3c2410_gpio_getpin(button_irqs[key].pin);

    if(!up)//低電平，按鍵按下
    {
        if(key_status[key] == KEY_UNCERTAIN)
        {
            //標識當前按鍵狀態為按下
			key_status[key] = KEY_DOWN;

            //標識當前按鍵已按下并喚醒等待隊列
            ev_press = 1;
            wake_up_interruptible(&button_waitq);
        }

        //設置當前按鍵抬起去抖定時器的延時并啟動定時器
        key_timers[key].expires = jiffies + KEY_TIMER_DELAY2;
        add_timer(&key_timers[key]);
    }
    else//高電平，按鍵抬起
    {
        //標識當前按鍵狀態為抬起
        key_status[key] = KEY_UP;
    }
}

static int buttons_open(struct inode *inode, struct file *file)
{
    int i;
    int ret;

    for(i = 0; i < KEY_COUNT; i++)
    {
        //設置6個IO口為中斷觸發方式
        s3c2410_gpio_cfgpin(button_irqs[i].pin, button_irqs[i].pin_setting);

        //設置中斷下降沿為有效觸發
	 set_irq_type(button_irqs[i].irq, IRQ_TYPE_EDGE_FALLING);
        
        //申請中斷(類型為快速中斷，中斷服務時屏蔽所有外部中斷？)
        ret = request_irq(button_irqs[i].irq, buttons_interrupt, IRQF_DISABLED, button_irqs[i].name, (void *)i);

        if(ret)
        {
            break;
        }

        //初始化6個按鍵的狀態為抬起
        key_status[i] = KEY_UP;

        //初始化并設置6個去抖定時器
        setup_timer(&key_timers[i], buttons_timer, i);
    }

    if(ret)
    {
        //中斷申請失敗處理
        i--;

        for(; i >= 0; i--)
        {
            //釋放已注冊成功的中斷
            disable_irq(button_irqs[i].irq);
            free_irq(button_irqs[i].irq, (void *)i);
        }

        return -EBUSY;
    }

    return 0;
}

static int buttons_close(struct inode *inode, struct file *file)
{
    int i;

    //釋放6個定時器和中斷
    for(i = 0; i < KEY_COUNT; i++)
    {
        del_timer(&key_timers[i]);

        disable_irq(button_irqs[i].irq);
        free_irq(button_irqs[i].irq, (void *)i);
    }

    return 0;
}

static int buttons_read(struct file *file, char __user *buf, size_t count, loff_t *offp)
{
    unsigned long ret;

    if(!ev_press)//判斷按鍵按下產生標識，0沒有產生
  {
        if(file->f_flags & O_NONBLOCK)
        {
            //應用程序若采用非阻塞方式讀取則返回錯誤
            return -EAGAIN;
        }
        else
        {
            //以阻塞方式讀取且按鍵按下沒有產生，讓等待隊列進入睡眠
            wait_event_interruptible(button_waitq, ev_press);
        }
    }

    //1為按鍵按下產生，并清除標識為0，準備給下一次判斷用
    ev_press = 0;

    //將內核中的按鍵狀態數據拷貝到用戶空間給應用程序使用
    ret = copy_to_user(buf, (void *)key_status, min(sizeof(key_status), count));

    return ret ? -EFAULT : min(sizeof(key_status), count);
}

//驅動程序中的輪詢，用于應用程序中的輪詢查詢是否可對設備進行訪問
static int buttons_poll(struct file *file, struct poll_table_struct *wait)
{
    unsigned int mask = 0;

    //添加等待隊列到等待隊列表中(poll_table)
 poll_wait(file, &button_waitq, wait);

    if(ev_press)
    {
        //標識數據可以獲得
        mask |= POLLIN | POLLRDNORM;
    }

    return mask;
}

//設備操作列表
static struct file_operations buttons_fops =
 {
    .owner        = THIS_MODULE,
    .open         = buttons_open,
    .release      = buttons_close,
    .read         = buttons_read,
    .poll         = buttons_poll,
};

static struct miscdevice misc = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = DEVICE_NAME,
	.fops = &buttons_fops,
};

static int __init button_init(void)
{
    int ret;
    //注冊字符設備
    ret = misc_register(&misc);

    if(ret < 0)
  {
        printk(DEVICE_NAME " register faild!\n");
        return ret;
    }

    return 0;
}

static void __exit button_exit(void)
{
    //注銷字符設備
   misc_deregister(&misc);
}

module_init(button_init);
module_exit(button_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Savager Lee");
MODULE_DESCRIPTION("mini2440 button driver");