linux驱动的异步通知（kill_fasync,fasync）---- 驱动程序向应用程序发送信号

应用程序

#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>


/* fifthdrvtest
  */
int fd;

//信号处理函数
void my_signal_fun(int signum)
{
    unsigned char key_val;
    read(fd, &key_val, 1);
    printf("key_val: 0x%x
", key_val);
}

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

    //在应用程序中捕捉SIGIO信号（由驱动程序发送）
    signal(SIGIO, my_signal_fun);

    fd = open("/dev/buttons", O_RDWR);
    if (fd < 0)
    {
        printf("can't open!
");
    }

    //将当前进程PID设置为fd文件所对应驱动程序将要发送SIGIO,SIGUSR信号进程PID
    fcntl(fd, F_SETOWN, getpid());

    //获取fd的打开方式
    Oflags = fcntl(fd, F_GETFL);

    //将fd的打开方式设置为FASYNC --- 即 支持异步通知
    // 该行代码执行会触发 驱动程序中 file_operations->fasync 函数 ------fasync函数调用 fasync_helper初始化一个fasync_struct结构体，该结构体描述了将要发送信号的进程 PID (fasync_struct->fa_file->f_owner->pid)
    fcntl(fd, F_SETFL, Oflags | FASYNC);


    while (1)
    {
        sleep(1000);
    }

    return 0;
}

驱动程序

#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 *fifthdrv_class;
static struct class_device  *fifthdrv_class_dev;

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

static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

/* 中断事件标志, 中断服务程序将它置1，fifth_drv_read将它清0 */
static volatile int ev_press = 0;

static struct fasync_struct *button_async;


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


/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
static unsigned char key_val;

/*
 * K1,K2,K3,K4对应GPG0，GPG3，GPG5，GPG6
 */

struct pin_desc pins_desc[4] = {
    {S3C2410_GPG0, 0x01},
    {S3C2410_GPG3, 0x02},
    {S3C2410_GPG5, 0x03},
    {S3C2410_GPG6, 0x04},
};


/*
  * 确定按键值
  */
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)
    {
        /* 松开 */
        key_val = 0x80 | pindesc->key_val;
    }
    else
    {
        /* 按下 */
        key_val = pindesc->key_val;
    }

    ev_press = 1;                  /* 表示中断发生了 */
    wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */

        //发送信号SIGIO信号给fasync_struct 结构体所描述的PID，触发应用程序的SIGIO信号处理函数
    kill_fasync (&button_async, SIGIO, POLL_IN);

    return IRQ_RETVAL(IRQ_HANDLED);
}

static int fifth_drv_open(struct inode *inode, struct file *file)
{
    /* GPG0，GPG3，GPG5，GPG6为中断引脚: EINT8,EINT11,EINT13,EINT14 */
    request_irq(IRQ_EINT8,  buttons_irq, IRQT_BOTHEDGE, "K1", &pins_desc[0]);
    request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "K2", &pins_desc[1]);
    request_irq(IRQ_EINT13, buttons_irq, IRQT_BOTHEDGE, "K3", &pins_desc[2]);
    request_irq(IRQ_EINT14, buttons_irq, IRQT_BOTHEDGE, "K4", &pins_desc[3]);

    return 0;
}

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

    /* 如果没有按键动作, 休眠 */
    wait_event_interruptible(button_waitq, ev_press);

    /* 如果有按键动作, 返回键值 */
    copy_to_user(buf, &key_val, 1);
    ev_press = 0;

    return 1;
}


int fifth_drv_close(struct inode *inode, struct file *file)
{
    free_irq(IRQ_EINT8,  &pins_desc[0]);
    free_irq(IRQ_EINT11, &pins_desc[1]);
    free_irq(IRQ_EINT13, &pins_desc[2]);
    free_irq(IRQ_EINT14, &pins_desc[3]);
    return 0;
}

static unsigned fifth_drv_poll(struct file *file, poll_table *wait)
{
    unsigned int mask = 0;
    poll_wait(file, &button_waitq, wait); // 不会立即休眠

    if (ev_press)
        mask |= POLLIN | POLLRDNORM;

    return mask;
}

static int fifth_drv_fasync (int fd, struct file *filp, int on)
{
    printk("driver: fifth_drv_fasync
");
    //初始化/释放 fasync_struct 结构体 (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,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
    .open    =  fifth_drv_open,
    .read    =  fifth_drv_read,
    .release =  fifth_drv_close,
    .poll    =  fifth_drv_poll,
    .fasync  =  fifth_drv_fasync,
};


int major;
static int fifth_drv_init(void)
{
    major = register_chrdev(0, "fifth_drv", &sencod_drv_fops);

    fifthdrv_class = class_create(THIS_MODULE, "fifth_drv");

    fifthdrv_class_dev = class_device_create(fifthdrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */

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

    return 0;
}

static void fifth_drv_exit(void)
{
    unregister_chrdev(major, "fifth_drv");
    class_device_unregister(fifthdrv_class_dev);
    class_destroy(fifthdrv_class);
//  iounmap(gpfcon);
    return 0;
}


module_init(fifth_drv_init);

module_exit(fifth_drv_exit);

MODULE_LICENSE("GPL");

http://blog.csdn.net/psvoldemort/article/details/21184525