驱动程序之_1_字符设备_4_fasync机制

fasync机制是异步通知机制，当驱动程序向应用程序发送信号量，触发应用程序的信号处理函数，以达到类似中断的效果

驱动程序中：
1、在文件专属的fasync函数中，调用了fasync_helper，将属主信息通知给内核
2、当发生按键中断，进入按键中断服务程序，读取键值，调用kill_fasync，发送信号量给相应进程

应用程序中：
1、使用signal，设置信号处理函数
2、使用fcntl(fd,F_SETOWN,getpid());，指定一个进程作为文件的属主，属主的进程ID号就保存在filp->f_owner中
3、fcntl获取、设置标志，设置标志的时候，最终会调用到文件专属的fasync函数
4、当有按键中断发生，驱动程序发送信号量，触发应用程序的信号处理函数，读取键值

附上驱动程序和测试用的应用程序代码

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>
#include <linux/device.h>
#include <linux/irq.h>

static struct class *my_irq_class;
static struct class_device *my_irq_class_device;

static unsigned char key_val;

struct fasync_struct *button_fasync;

static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

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

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

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)
	{
		key_val = 0x80 | pindesc->key_val;
	}
	else
	{
		key_val = pindesc->key_val;
	}

	kill_fasync(&button_fasync, SIGIO, POLL_IN);

	return IRQ_HANDLED;
}

static int my_irq_drv_open(struct inode *inode, struct file *file)
{
	request_irq(IRQ_EINT0,buttons_irq,IRQT_BOTHEDGE,"S2",&key_pins_desc[0]);
	request_irq(IRQ_EINT2,buttons_irq,IRQT_BOTHEDGE,"S3",&key_pins_desc[1]);
	request_irq(IRQ_EINT11,buttons_irq,IRQT_BOTHEDGE,"S4",&key_pins_desc[2]);
	request_irq(IRQ_EINT19,buttons_irq,IRQT_BOTHEDGE,"S5",&key_pins_desc[3]);	

	return 0;
}

int my_irq_drv_close(struct inode *inode,struct file *file)
{
	free_irq(IRQ_EINT0,&key_pins_desc[0]);
	free_irq(IRQ_EINT2,&key_pins_desc[1]);
	free_irq(IRQ_EINT11,&key_pins_desc[2]);
	free_irq(IRQ_EINT19,&key_pins_desc[3]);
	
	return 0;
}

ssize_t my_irq_drv_read(struct file *file, char __user *buf, size_t size, loff_t * ppos)
{

	if(size != 1)
		return -EINVAL;

	copy_to_user(buf,&key_val,1);

	return 0;
}

static int my_irq_drv_fasync(int fd,struct file *filp,int on)
{
	return fasync_helper(fd,filp,on,&button_fasync);
}

static struct file_operations irq_drv_fops = {
	.owner = THIS_MODULE,
	.open = my_irq_drv_open,
	.read = my_irq_drv_read,
	.release = my_irq_drv_close,
	.fasync = my_irq_drv_fasync,
};

static int major;

static int my_irq_drv_init(void)
{
	major = register_chrdev(0,"my_irq_drv",&irq_drv_fops);
	my_irq_class = class_create(THIS_MODULE,"my_irq_drv");
	my_irq_class_device = class_device_create(my_irq_class,NULL,MKDEV(major,0),NULL,"key_irq_drv");

	return 0;
}

static void my_irq_drv_exit(void)
{
	unregister_chrdev(major,"my_irq_drv");
	class_device_unregister(my_irq_class_device);
	class_destroy(my_irq_class);
}

module_init(my_irq_drv_init);
module_exit(my_irq_drv_exit);
MODULE_LICENSE("GPL");

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

static int fd;

void my_signal_fun(int signum)
{
	static int cnt = 0;
	unsigned char key_val;
	read(fd,&key_val,1);		
	printf("press key : 0x%02x , signum : %d , cnt : %d\r\n",key_val,signum,++cnt);
}

int main(int argc,char *args[])
{
	int oflags;
	
	signal(SIGIO,my_signal_fun);
	
	fd = open("/dev/key_irq_drv",O_RDWR);
	if(fd < 0)
	{
		printf("can't open\r\n");
		return 0;
	}
	printf("open successfully\r\n");

	fcntl(fd,F_SETOWN,getpid());
	oflags = fcntl(fd,F_GETFL);
	fcntl(fd,F_SETFL,oflags | FASYNC);

	while(1)
	{
		sleep(1000);			
	}

	return 0;
}