字符设备驱动 -- 异步通知解析

字符设备驱动 -- 异步通知解析。

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

static struct class *fifthdrv_class;
static struct class_device	*fifthdrv_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;

struct pin_desc pins_desc[4] = {
	{S3C2410_GPF0, 0x01},
	{S3C2410_GPF2, 0x02},
	{S3C2410_GPG3, 0x03},
	{S3C2410_GPG11, 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 */
	
	kill_fasync (&button_async, SIGIO, POLL_IN);
	
	return IRQ_RETVAL(IRQ_HANDLED);
}

static int fifth_drv_open(struct inode *inode, struct file *file)
{
	/* 配置GPF0,2为输入引脚 */
	/* 配置GPG3,11为输入引脚 */
	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 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_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]);
	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\n");
	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;

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


module_init(fifth_drv_init);
module_exit(fifth_drv_exit);
MODULE_LICENSE("GPL");

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 


/* fifthdrvtest 
  */
int fd;

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;

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

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


	while (1)
	{
		sleep(1000);
	}
	
	return 0;
}

代码出自“韦东山视频”。

1、fasync是为了使驱动的读写和应用程序的读写分开，使得应用程序可以在驱动读写的时候去做别的事。

2、fasync_helper初始化fasync，包括分配内存和设置属性。

3、kill_fasync (&button_async, SIGIO, POLL_IN)，发SIGIO信号给应用程序；

应用程序就调用自己安装的响应函数去处理，signal(SIGIO, my_signal_fun)。

4、fcntl(fd, F_SETFL, Oflags | FASYNC)，设置FASYNC属性。