第3课.Linux异常处理体系结构

1.裸机和linux中断

裸机中断流程

1.外部触发
2.CPU发生中断，强制跳到异常向量处
3.跳到具体函数
    a.保存具体函数
    b.处理具体函数
    c.恢复中断现场

linux中断

ARM架构的CPU的异常向量基地址可以是0x00000000或0xffff0000这个地址并不是物理地址，是虚拟地址，需要建立物理地址与虚拟地址的映射。所谓"向量"，就是一些被安放在固定位置的代码，当发生异常时，CPU会自动执行这些固定位置上的指令。ARM架构CPU的异常向量基地址可以是0x00000000，也可以是0xffff0000，linux呃逆和使用后者。

2.linux内核中断处理函数

request_irq（用户注册中断处理函数）

static inline int __must_check
request_irq(unsigned int irq, irq_handler_t handler, unsigned long flags,
	    const char *name, void *dev)
irq：中断号
handler：中断函数
flags：触发类型
name：名字
dev：设备id，主要是和irq一起结合起来确定是哪一个。可以较为随意的设置

free_irq（卸载中断处理函数）

void free_irq(unsigned int irq, void *dev_id)

3.wait_event_interruptible和wait_up_interruptible

wait_event_interruptible(休眠当前进程，不向下继续执行)

eg：
    static DECLARE_WAIT_QUEUE_HEAD(button_waitq);        //定义一个等待队列

    wait_event_interruptible(button_waitq, ev_press);
wait_event_interruptible首先会判断ev_press是否为0，如果为0才会令当前进程进入休眠；否则向下继续执行。它的第一个参数button_waitq是一个等待队列，第二个参数ev_press用来表示中断是否发生，在中断服务程序中把它置为1.

wait_up_interruptible(唤醒休眠进程)

eg：
    wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */

4.代码解析

Makefile

KERN_DIR = /work/system/linux-2.6.22.6

all:
	make -C $(KERN_DIR) M=`pwd` modules 

clean:
	make -C $(KERN_DIR) M=`pwd` modules clean
	rm -rf modules.order

obj-m	+= third_drv.o

third_drv.c

#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>


static struct class *thirddrv_class;
static struct class_device	*thirddrv_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，third_drv_read将它清0 */
static volatile int ev_press = 0;


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 */

	
	return IRQ_RETVAL(IRQ_HANDLED);
}

static int third_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 third_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 third_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 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    =  third_drv_open,     
	.read	 =	third_drv_read,	   
	.release =  third_drv_close,	   
};


int major;
static int third_drv_init(void)
{
	major = register_chrdev(0, "third_drv", &sencod_drv_fops);

	thirddrv_class = class_create(THIS_MODULE, "third_drv");

	thirddrv_class_dev = class_device_create(thirddrv_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 third_drv_exit(void)
{
	unregister_chrdev(major, "third_drv");
	class_device_unregister(thirddrv_class_dev);
	class_destroy(thirddrv_class);
	iounmap(gpfcon);
	iounmap(gpgcon);
	return 0;
}


module_init(third_drv_init);

module_exit(third_drv_exit);

MODULE_LICENSE("GPL");

thirddrvtest.c

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

/* thirddrvtest 
  */
int main(int argc, char **argv)
{
	int fd;
	unsigned char key_val;
	
	fd = open("/dev/buttons", O_RDWR);
	if (fd < 0)
	{
		printf("can't open!
");
	}

	while (1)
	{
		//read(fd, &key_val, 1);
		//printf("key_val = 0x%x
", key_val);
		sleep(5);
	}
	
	return 0;
}