当按下中断后，发生中断，发生以下事情
1.CPU进入异常模式，并跳转到vector_irq + stubs_offset处
2.因为在用户模式发生中断，所以跳转到__irq_usr指示的地址处
3.最终跳转到函数asm_do_IRQ处
4.在asm_do_IRQ按中断号查找到对应中断的irq_desc描述符，然后进入中断处理入口handle_irq
5.接着调用generic_handle_irq_desc
6.desc->handle_irq(irq,desc)，而这个是在中断架构初始化的时候设置的
7.接着使能中断，调用用户注册的中断处理例程链表
8.处理完成后，恢复现场
Linux驱动程序开发之三—-按键驱动（Tiny6410）差不多，只是重新设计了数据结构buttons_irq_desc，并且增加了自动创建设备节点的功能。
struct button_irq_desc { int irq; int number; char *name;};static struct button_irq_desc button_irqs [] = { {IRQ_EINT( 0), 0, "KEY0"}, {IRQ_EINT( 1), 1, "KEY1"}, {IRQ_EINT( 2), 2, "KEY2"}, {IRQ_EINT( 3), 3, "KEY3"}, {IRQ_EINT( 4), 4, "KEY4"}, {IRQ_EINT( 5), 5, "KEY5"}, {IRQ_EINT(19), 6, "KEY6"}, {IRQ_EINT(20), 7, "KEY7"},};
在里面增加了number字段值，用于指示是第几个按键被按下，上次博文中出现的不能注册K5,6,7,8的中断问题也已经解决，是内核编译的时候可能有点错误，使用make menuconfig将device driver -> char ->中有关mini6410的配置全部去掉后，再次编译OK了！所以中断处理程序中可以将其值保存到一个全局变量中,然后唤醒休眠队列上的进程，read函数中检测是否有键被按下，若没有则将进程挂起，否则将中断中保存的键号值拷贝到用户空间，在用户程序中将这个值打印出来。
源码如下：
/* * *buttons驱动程序TIny6410 *使用标准字符设备驱动编写方法 *make完成后根据打印到终端的输出，创建字符设备 *格式如下: *mknod /dev/buttons c 主设备号 0 *目前存在一些问题，只能驱动按键K1~K4,不能驱动K5~K7,原因是request_irq函数调用失败 *另外，使用ctrl+c中断后再次加载驱动会失败，原因不清楚 *Author:jefby *Email:jef199006@gmail.com * */#include <linux/module.h>//MODULE_LICENSE,MODULE_AUTHOR#include <linux/init.h>//module_init/module_exit#include <linux/fs.h>//file_operations#include <asm/io.h>//ioread32,iowrite32#include <linux/cdev.h>//cdev#include <mach/map.h>//定义了S3C64XX_VA_GPIO#include <mach/regs-gpio.h>//定义了gpio-bank-n中使用的S3C64XX_GPN_BASE#include <mach/gpio-bank-n.h>//定义了GPNCON#include <mach/gpio-bank-l.h>//定义了GPNCON#include <linux/wait.h>//wait_event_interruptible(wait_queue_head_t q,int condition);//wake_up_interruptible(struct wait_queue **q)#include <linux/sched.h>//request_irq,free_irq#include <asm/uaccess.h>//copy_to_user#include <linux/irq.h>//IRQ_TYPE_EDGE_FALLING#include <linux/interrupt.h>//request_irq,free_irq#include <linux/device.h>//class deviceMODULE_AUTHOR("jefby");MODULE_LICENSE("Dual BSD/GPL");MODULE_DESCRIPTION("Tiny 6410 buttons with interrupt");#define GPNCON 0x7F008830#define GPNDAT 0x7F008834#define GPLCON0 0x7F008810#define GPLDAT 0x7F008818struct button_irq_desc { int irq; int number; char *name;};static struct button_irq_desc button_irqs [] = { {IRQ_EINT( 0), 0, "KEY0"}, {IRQ_EINT( 1), 1, "KEY1"}, {IRQ_EINT( 2), 2, "KEY2"}, {IRQ_EINT( 3), 3, "KEY3"}, {IRQ_EINT( 4), 4, "KEY4"}, {IRQ_EINT( 5), 5, "KEY5"}, {IRQ_EINT(19), 6, "KEY6"}, {IRQ_EINT(20), 7, "KEY7"},};//声明一个按键的等待队列static DECLARE_WAIT_QUEUE_HEAD(buttons_waitq);//指示是否有按键被按下，在中断处理程序中置为，read程序将其清0static volatile int ev_press = 0;//按键设备的主设备号static int buttons_major = 0;//设备号dev_t dev;//字符设备struct cdev * buttons_cdev=NULL;static volatile unsigned char key_val = 0;static struct class * tiny6410_buttons_class = NULL;static struct device * tiny6410_buttons_device = NULL;//按下次数//中断处理程序，记录按键按下的次数，并置标志位为1，唤醒等待队列上等待的进程static irqreturn_t buttons_interrupt(int irq,void *dev_id){struct button_irq_desc *temp = (struct button_irq_desc *)dev_id;key_val = (unsigned char)(temp->number+1);ev_press = 1;//表示中断发生了wake_up_interruptible(&buttons_waitq);return IRQ_RETVAL(IRQ_HANDLED);}//设备打开操作，主要完成BUTTONS所对应的GPIO的初始化，注册用户中断处理函数,设置触发方式为双边沿触发int buttons_open(struct inode *inode,struct file *filp){ int i; int err = 0; //申请中断号 for (i = 0; i < sizeof(button_irqs)/sizeof(button_irqs[0]); i++) {if (button_irqs[i].irq < 0) {continue;} err = request_irq(button_irqs[i].irq, buttons_interrupt, IRQ_TYPE_EDGE_BOTH, button_irqs[i].name, (void *)&button_irqs[i]); if (err) break; } if (err) { printk("err=%d.\n",err); i--; for (; i >= 0; i--) { if (button_irqs[i].irq < 0) {continue; } disable_irq(button_irqs[i].irq); free_irq(button_irqs[i].irq, (void *)&button_irqs[i]); } return -EBUSY; } ev_press = 0;//设置初始状态为0 return 0;}//按键读若没有键被按下，则使进程休眠；若有按键被按下，则拷贝数据到用户空间，然后清零int buttons_read(struct file *filp, char __user *buf, size_t len, loff_t * pos){unsigned long val = 0;if(len != sizeof(key_val))return -EINVAL;wait_event_interruptible(buttons_waitq,ev_press);//ev_press==0,则休眠ev_press = 0;//重新清0if((val = copy_to_user(buf,(const void*)&key_val,sizeof(key_val))) != sizeof(key_val))return -EINVAL;return sizeof(key_val);}//主要是卸载用户中断处理程序int buttons_close(struct inode *inode,struct file *filp){int i=0;printk("buttons close.\n");for (i = 0; i < sizeof(button_irqs)/sizeof(button_irqs[0]); i++) {disable_irq(button_irqs[i].irq);free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);}return 0;}static struct file_operations buttons_fops = {.owner = THIS_MODULE,.read = buttons_read,.release = buttons_close,.open = buttons_open,};/*模块初始化：1.申请设备号，默认使用动态分配的方法2.申请并初始化cdev结构3.将cdev注册到内核*/static int module_buttons_init(void){int result;int err=0;printk("Tiny6410 buttons module init.\n");if(buttons_major){dev = MKDEV(buttons_major,0);result = register_chrdev_region(dev,1,"buttons");}else{result = alloc_chrdev_region(&dev,0,1,"buttons");buttons_major = MAJOR(dev);}if(result < 0){printk(KERN_WARNING "buttons : can't get major %d\n",buttons_major);}printk("buttons major is %d",buttons_major);buttons_cdev = cdev_alloc();buttons_cdev ->ops = &buttons_fops;cdev_init(buttons_cdev,&buttons_fops);cdev_add(buttons_cdev,dev,1);tiny6410_buttons_class = class_create(THIS_MODULE, "tiny6410buttons");if (IS_ERR(tiny6410_buttons_class)) {err = PTR_ERR(tiny6410_buttons_class);printk("create class error.\n");}tiny6410_buttons_device = device_create(tiny6410_buttons_class, NULL, MKDEV(buttons_major, 0), NULL, "buttons");printk("buttons add ok.\n");return 0;}static void module_buttons_exit(void){device_destroy(tiny6410_buttons_class, MKDEV(buttons_major, 0));class_destroy(tiny6410_buttons_class);cdev_del(buttons_cdev);unregister_chrdev_region(dev,1);printk("Tiny6410 buttons module exit");}module_init(module_buttons_init);module_exit(module_buttons_exit);
用户程序如下：
#include <unistd.h>#include <sys/ioctl.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <sys/select.h>#include <sys/time.h>#include <errno.h>static int cnt=0;int main(void){int buttons_fd;unsigned char buttons=0 ;buttons_fd = open("/dev/buttons", 0);if (buttons_fd < 0) {perror("open device buttons");return -1;}while(1){read(buttons_fd, &buttons, sizeof (buttons));printf("%dKEY%02x entered.\n",cnt++,buttons);}close(buttons_fd);return 0;}
下载运行测试截图：
你在无垠的海边第一次听到了自己心跳的声音，
