Linux内核中断引入用户空间（异步通知机制）【转】

转自：http://blog.csdn.net/kingdragonfly120/article/details/10858647

版权声明：本文为博主原创文章，未经博主允许不得转载。

        当Linux内核空间发生中断后怎么使用户空间的应用程序运行相应的函数呢，当芯片有数据到来时内核会产生一个中断，但是怎样通知应用程序来取数据，以前这个问题一直困扰我很长时间，后来发现linux中有异步通知机制，在用户程序中用signal注册一个响应SIGIO信号的回调函数，然后在驱动程序中向该进程发出SIGIO信号便完成该功能，下面是该功能具体实施方法：

1.在驱动中定义一个static struct fasync_struct *async;

2.在fasync系统调用中注册fasync_helper(fd, filp, mode, &async);

3.在中断服务程序（顶半部、底半部都可以）发出信号kill_fasync(&async, SIGIO, POLL_IN);

4.在用户应用程序中用signal注册一个响应SIGIO的回调函数signal(SIGIO, sig_handler);

5.通过fcntl(fd, F_SETOWN, getpid())将将进程pid传入内核

6.通过fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | FASYNC)设置异步通知

 

驱动部分代码：

 

 

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <asm/io.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/gpio.h>
#include <mach/regs-gpio.h>
#include <asm-generic/siginfo.h>
#include <linux/init.h>
#include <asm/signal.h>
#include <linux/timer.h>
#include <asm/uaccess.h>

#define DEVICE_NAME "mybeep"

volatile unsigned long *GPBCON;
volatile unsigned long *GPBDAT;
volatile unsigned long *GPBUP;
void beep_start(void);
void beep_stop(void);
int  beep_irq_register(void);
unsigned int flag=1;

static struct fasync_struct *async; //声明fasync_struct
struct key_irq_desc {
    unsigned int irq;
    int pin;
    int pin_setting;
    int number;
    char *name;
};

static int beep_fasync(int fd, struct file *filp, int mode)
{
    printk("application  fasync!
");
    return fasync_helper(fd, filp, mode, &async);         //注册上层调用进程的信息，上层调用fcntl设置FASYNC会调用这个系统调用
}

static struct key_irq_desc key_irqs [] = {
    {IRQ_EINT8, S3C2410_GPG(0), S3C2410_GPG0_EINT8, 0, "KEY1"},
};

static irqreturn_t key_interrupt(int irq, void *dev_id)
{
    kill_fasync(&async, SIGIO, POLL_IN);  //向打开设备文件的进程发出SIGIO信号
    return (IRQ_HANDLED);
}

void beep_gpiob_init(void)
{
    *GPBCON&=~((1<<0)|(1<<1));
    *GPBCON|=(1<<0);
    *GPBUP&=~(1<<0);
}

void beep_start(void)
{
    *GPBDAT|=(1<<0);
}

void beep_stop(void)
{
    *GPBDAT&=~(1<<0);
}

int beep_open(struct inode *inode, struct file *filp)
{
    if(beep_irq_register() != 0)
    {
        printk("Request irq error!
");
    }
    printk(KERN_ALERT "application  open!
");
    return 0;
}

ssize_t beep_read(struct file *file, char __user *buff, size_t count, loff_t *offp)
{
    printk("application  read!
");
    return 0;
}

ssize_t beep_write(struct file *file, const char __user *buff, size_t count, loff_t *offp)
{
    printk("application  write!
");
    return 0;
}

static int beep_release(struct inode *inode, struct file *file)
{
    disable_irq(key_irqs[0].irq);
    free_irq(key_irqs[0].irq, (void *)&key_irqs[0]);
    printk("application  close!
");
    return beep_fasync(-1, file, 0);
}

static int beep_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
    switch(cmd)
    {
    case 0:
        beep_start();
        break;
    case 1:
        beep_stop();
        break;
    default:
        break;
    }
    return 0;
}

static struct file_operations beep_ops = {
    .owner = THIS_MODULE,
    .open = beep_open,
    .release = beep_release,
    .ioctl = beep_ioctl,
    .read = beep_read,
    .write = beep_write,
    .fasync = beep_fasync,
};

static struct miscdevice beep_misc = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = DEVICE_NAME,
    .fops = &beep_ops,
};

int beep_irq_register(void)
{
    int err;
    err = request_irq(key_irqs[0].irq, key_interrupt, 0, key_irqs[0].name, (void *)&key_irqs[0]);
    set_irq_type(key_irqs[0].irq, IRQ_TYPE_EDGE_RISING);
    if(err)
    {
        disable_irq(key_irqs[0].irq);
        free_irq(key_irqs[0].irq, (void *)&key_irqs[0]);
        return -EBUSY;
    }
    return 0;
}

static int __init beep_init(void)
{
    int ret;
    ret=misc_register(&beep_misc);
    if(ret <0)
    {
        printk("register miscdevice error code:%d
",ret);
        return ret;
    }
    printk("beep device create!
");
    GPBCON=(volatile unsigned long *)ioremap(0x56000010,12);
    GPBDAT=GPBCON+1;
    GPBUP=GPBCON+2;
    beep_gpiob_init();
    return 0;
}

static void __exit beep_exit(void)
{
    iounmap(GPBCON);
    misc_deregister(&beep_misc);
    printk("beep device delete!
");
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("kingdragonfly");
module_init(beep_init);
module_exit(beep_exit);

用户应用程序代码：

 

#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>

void sig_handler(int sig)
{
    if(sig == SIGIO)
    {
        printf("Receive io signal from kernel!
");
    }
}

int main(void)
{
    int fd;
    signal(SIGIO, sig_handler);
    fd = open("/dev/mybeep",O_RDWR);
    fcntl(fd, F_SETOWN, getpid());
    fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | FASYNC);
    printf("waiting key interrupt:
");
    while(1)
    {
    }
}

当内核里发生中断时在中断服务程序中发出SIGIO信号从而自动调用相应的回调函数，在回调函数中可以进行相应处理。

上面程序在mini2440开发板实现了按K1键，用户程序自动调用void sig_handler(int sig)功能