===========================應用程式=========================

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <poll.h>
#include <signal.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>

/* sixthdrvtest 
  */
int fd;

//訊號處理函式

void my_signal_fun(int signum)
{
    unsigned char key_val;
    read(fd, &key_val, 1);
    printf("key_val: 0x%x\n", key_val);
}

int main(int argc, char **argv)
{
    unsigned char key_val;
    int ret;
    int Oflags;

//在應用程式中捕捉SIGIO訊號（由驅動程式傳送）

    //signal(SIGIO, my_signal_fun);
    
    fd = open("/dev/buttons", O_RDWR | O_NONBLOCK);
    if (fd < 0)
    {
        printf("can't open!\n");
        return -1;
    }

//將當前程序PID設定為fd檔案所對應驅動程式將要傳送SIGIO,SIGUSR訊號程序PID

    //fcntl(fd, F_SETOWN, getpid());
    
    //Oflags = fcntl(fd, F_GETFL); 

//將fd的開啟方式設定為FASYNC --- 即 支援非同步通知
    //該行程式碼執行會觸發 驅動程式中 file_operations->fasync 函式 ------fasync函式呼叫fasync_helper初始化一個fasync_struct結構體，該結構體描述了將要傳送訊號的程序PID (fasync_struct->fa_file->f_owner->pid)
    //fcntl(fd, F_SETFL, Oflags | FASYNC);

    while (1)
    {
        ret = read(fd, &key_val, 1);
        printf("key_val: 0x%x, ret = %d\n", key_val, ret);
        sleep(5);
    }
    
    return 0;
}

===========================驅動程式=========================

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>
#include <linux/poll.h>

static struct class *sixthdrv_class;
static struct class_device    *sixthdrv_class_dev;

volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;

volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;

static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

/* 中斷事件標誌, 中斷服務程式將它置1，sixth_drv_read將它清0 */
static volatile int ev_press = 0;

static struct fasync_struct *button_async;

struct pin_desc{
    unsigned int pin;
    unsigned int key_val;
};

/* 鍵值: 按下時, 0x01, 0x02, 0x03, 0x04 */
/* 鍵值: 鬆開時, 0x81, 0x82, 0x83, 0x84 */
static unsigned char key_val;

struct pin_desc pins_desc[4] = {
    {S3C2410_GPF0, 0x01},
    {S3C2410_GPF2, 0x02},
    {S3C2410_GPG3, 0x03},
    {S3C2410_GPG11, 0x04},
};

//static atomic_t canopen = ATOMIC_INIT(1);     //定義原子變數並初始化為1

static DECLARE_MUTEX(button_lock);     //定義互斥鎖

/*
  * 確定按鍵值
  */
static irqreturn_t buttons_irq(int irq, void *dev_id)
{
    struct pin_desc * pindesc = (struct pin_desc *)dev_id;
    unsigned int pinval;
    
    pinval = s3c2410_gpio_getpin(pindesc->pin);

    if (pinval)
    {
        /* 鬆開 */
        key_val = 0x80 | pindesc->key_val;
    }
    else
    {
        /* 按下 */
        key_val = pindesc->key_val;
    }

    ev_press = 1;                  /* 表示中斷髮生了 */
    wake_up_interruptible(&button_waitq);   /* 喚醒休眠的程序 */

    //傳送訊號SIGIO訊號給fasync_struct 結構體所描述的PID，觸發應用程式的SIGIO訊號處理函式
    kill_fasync (&button_async, SIGIO, POLL_IN);
    
    return IRQ_RETVAL(IRQ_HANDLED);
}

static int sixth_drv_open(struct inode *inode, struct file *file)
{
#if 0    
    if (!atomic_dec_and_test(&canopen))
    {
        atomic_inc(&canopen);
        return -EBUSY;
    }
#endif        

    if (file->f_flags & O_NONBLOCK)
    {
        if (down_trylock(&button_lock))
            return -EBUSY;
    }
    else
    {
        /* 獲取訊號量 */
        down(&button_lock);
    }

    /* 配置GPF0,2為輸入引腳 */
    /* 配置GPG3,11為輸入引腳 */
    request_irq(IRQ_EINT0,  buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);
    request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);
    request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);
    request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);    

    return 0;
}

ssize_t sixth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
    if (size != 1)
        return -EINVAL;

    if (file->f_flags & O_NONBLOCK)
    {
        if (!ev_press)
            return -EAGAIN;
    }
    else
    {
        /* 如果沒有按鍵動作, 休眠 */
        wait_event_interruptible(button_waitq, ev_press);
    }

    /* 如果有按鍵動作, 返回鍵值 */
    copy_to_user(buf, &key_val, 1);
    ev_press = 0;
    
    return 1;
}

int sixth_drv_close(struct inode *inode, struct file *file)
{
    //atomic_inc(&canopen);
    free_irq(IRQ_EINT0, &pins_desc[0]);
    free_irq(IRQ_EINT2, &pins_desc[1]);
    free_irq(IRQ_EINT11, &pins_desc[2]);
    free_irq(IRQ_EINT19, &pins_desc[3]);
    up(&button_lock);
    return 0;
}

static unsigned sixth_drv_poll(struct file *file, poll_table *wait)
{
    unsigned int mask = 0;
    poll_wait(file, &button_waitq, wait); // 不會立即休眠

    if (ev_press)
        mask |= POLLIN | POLLRDNORM;

    return mask;
}

static int sixth_drv_fasync (int fd, struct file *filp, int on)
{
    printk("driver: sixth_drv_fasync\n");

//初始化/釋放 fasync_struct 結構體 (fasync_struct->fa_file->f_owner->pid)
    return fasync_helper (fd, filp, on, &button_async);
}

static struct file_operations sencod_drv_fops = {
    .owner   =  THIS_MODULE,    /* 這是一個巨集，推向編譯模組時自動建立的__this_module變數 */
    .open    =  sixth_drv_open,     
    .read     =    sixth_drv_read,       
    .release =  sixth_drv_close,
    .poll    =  sixth_drv_poll,
    .fasync     =  sixth_drv_fasync,
};

int major;
static int sixth_drv_init(void)
{
    major = register_chrdev(0, "sixth_drv", &sencod_drv_fops);

    sixthdrv_class = class_create(THIS_MODULE, "sixth_drv");

    sixthdrv_class_dev = class_device_create(sixthdrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */

    gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
    gpfdat = gpfcon + 1;

    gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);
    gpgdat = gpgcon + 1;

    return 0;
}

static void sixth_drv_exit(void)
{
    unregister_chrdev(major, "sixth_drv");
    class_device_unregister(sixthdrv_class_dev);
    class_destroy(sixthdrv_class);
    iounmap(gpfcon);
    iounmap(gpgcon);
    return 0;
}

module_init(sixth_drv_init);

module_exit(sixth_drv_exit);

MODULE_LICENSE("GPL");