Linux內核中斷引入用戶空間（異步通知機制）

當linux內核空間發生中斷後怎麼使用戶空間的應用程序運行相應的函數呢，當芯片有數據到來時內核會產生一箇中斷，但是怎樣通知應用程序來取數據，以前這個問題一直困擾我很長時間，後來發現linux中有異步通知機制，在用戶程序中用signal註冊一個響應SIGIO信號的回調函數，然後在驅動程序中向該進程發出SIGIO信號便完成該功能，下面是該功能具體實施方法：

1.在驅動中定義一個static struct fasync_struct *async;

2.在fasync系統調用中註冊fasync_helper(fd, filp, mode, &async);

3.在中斷服務程序（頂半部、底半部都可以）發出信號kill_fasync(&async, SIGIO, POLL_IN);

4.在用戶應用程序中用signal註冊一個響應SIGIO的回調函數signal(SIGIO, sig_handler);

5.通過fcntl(fd, F_SETOWN, getpid())將將進程pid傳入內核

6.通過fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | FASYNC)設置異步通知

驅動部分代碼：

#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; //聲明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!\n");
    return fasync_helper(fd, filp, mode, &async);         //註冊上層調用進程的信息，上層調用fcntl設置FASYNC會調用這個系統調用
}

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);  //向打開設備文件的進程發出SIGIO信號
    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!\n");
    }
    printk(KERN_ALERT "application  open!\n");
    return 0;
}

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

ssize_t beep_write(struct file *file, const char __user *buff, size_t count, loff_t *offp)
{
    printk("application  write!\n");
    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!\n");
    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\n",ret);
        return ret;
    }
    printk("beep device create!\n");
    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!\n");
}

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

用戶應用程序代碼：

#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!\n");
    }
}

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:\n");
    while(1)
    {
    }
}

當內核裏發生中斷時在中斷服務程序中發出SIGIO信號從而自動調用相應的回調函數，在回調函數中可以進行相應處理。

上面程序在mini2440開發板實現了按K1鍵，用戶程序自動調用void sig_handler(int sig)功能