这节，我们继续上，中(以前的日志有)篇目进行分析，结合一个真实的驱动案例来描述linux内核中驱动的中断机制，首先我们先了解一下linux内核中提供的中断接口。
这个接口我们需要包含一个头文件:#include <linux/interrupt.h>
在中断接口中，最重要的是以下的接口函数:
1、这个是请求中断函数
int request_irq(unsigned int irq, irq_handler_t handler, unsigned long irqflags, const char *devname, void *dev_id) irq: 中断号 arch/arm/plat-s3c64xx/include/plat/irqs.h handler: 中断处理函数 irqreturn_t handler(int irq, void *dev_id); irqreturn_t: See include/linux/irqreturn.h irqflags: See line 21-59 in include/linux/interrupt.h 使用IRQF_SHARED共享irq时, irqflags必须相同 如: request_irq(IRQ_EINT(0), handler1, IRQF_TRIGGER_FALLING | IRQF_SHARED, "dev1", &dev1); request_irq(IRQ_EINT(0), handler2, IRQF_TRIGGER_FALLING | IRQF_SHARED, "dev2", &dev2); devname: 设备名, cat /proc/interrupts dev_id: 发生中断时将dev_id传递给handler函数, irqflags含有IRQF_SHARED时dev_id不能为NULL, 并且要保证唯一 dev_id一般采用当前设备的结构体指针2、释放中断
void free_irq ( unsigned int irq, void * dev_id); 释放匹配irq和dev_id的中断, 如果irq有多个相同的dev_id, 将释放第一个 So, 共享中断的dev_id不是唯一时, 可能会释放到其它设备的中断3、开启中断
void enable_irq(unsigned int irq); 开启irq号中断4、关闭中断
void disable_irq(unsigned int irq); 关闭irq号中断5、关闭当前CPU中断并保存在flag中去
void local_irq_save(unsigned long flags);6、恢复flag到CPU中去
void local_irq_restore(unsigned long flags); 恢复flags到当前CPU7、关闭当前的CPU中断
void local_irq_disable(void);8、开始当前的CPU中断
void local_irq_enable(void);接下来我们来看一个按键中断的例子，这个例子是基于Tiny4412按键驱动的源码:
#include <linux/module.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/delay.h>#include <linux/poll.h>#include <linux/sched.h>#include <linux/irq.h>#include <asm/irq.h>#include <asm/io.h>#include <linux/interrupt.h>#include <asm/uaccess.h>#include <mach/hardware.h>#include <linux/platform_device.h>#include <linux/cdev.h>#include <linux/miscdevice.h>#include <linux/gpio.h>#include <mach/map.h>#include <mach/gpio.h>#include <mach/regs-clock.h>#include <mach/regs-gpio.h>//设备名称#define DEVICE_NAME "buttons"struct button_desc { int gpio; int number; char *name; struct timer_list timer;};//定义按键相关的寄存器static struct button_desc buttons[] = { { EXYNOS4_GPX3(2), 0, "KEY0" }, { EXYNOS4_GPX3(3), 1, "KEY1" }, { EXYNOS4_GPX3(4), 2, "KEY2" }, { EXYNOS4_GPX3(5), 3, "KEY3" },};//存储按键的键值static volatile char key_values[] = { '0', '0', '0', '0', '0', '0', '0', '0'};//创建一个等待队列头并初始化static DECLARE_WAIT_QUEUE_HEAD(button_waitq);static volatile int ev_press = 0;//按键定时器static void tiny4412_buttons_timer(unsigned long _data){ struct button_desc *bdata = (struct button_desc *)_data; int down; int number; unsigned tmp; //获取按键的值 tmp = gpio_get_value(bdata->gpio); //判断是否为低电平 down = !tmp; printk(KERN_DEBUG "KEY %d: %08x\n", bdata->number, down); number = bdata->number; //如果此时不为低电平，中断处理进入休眠状态，一般有事件产生就会立即被唤醒 if (down != (key_values[number] & 1)) { key_values[number] = '0' + down; ev_press = 1; //中断休眠 wake_up_interruptible(&button_waitq); }}//按键中断处理函数//irq：中断号//dev_id:设备ID号static irqreturn_t button_interrupt(int irq, void *dev_id){ struct button_desc *bdata = (struct button_desc *)dev_id; //注册一个定时器 mod_timer(&bdata->timer, jiffies + msecs_to_jiffies(40)); //返回一个中断句柄 return IRQ_HANDLED; }//按键打开函数//inode : 节点//file : 打开文件的形式static int tiny4412_buttons_open(struct inode *inode, struct file *file){ int irq; int i; int err = 0; //循环遍历四个IO口，看看有哪个按键被按下了 for (i = 0; i < ARRAY_SIZE(buttons); i++) { if (!buttons[i].gpio) continue; //初始化定时器 setup_timer(&buttons[i].timer, tiny4412_buttons_timer, (unsigned long)&buttons[i]); //设置GPIO为中断引脚，也就是对应那四个按键 irq = gpio_to_irq(buttons[i].gpio); err = request_irq(irq, button_interrupt, IRQ_TYPE_EDGE_BOTH, //请求中断处理函数 buttons[i].name, (void *)&buttons[i]); if (err) break; } if (err) { i--; for (; i >= 0; i--) { if (!buttons[i].gpio) continue; irq = gpio_to_irq(buttons[i].gpio); disable_irq(irq); //关中断 free_irq(irq, (void *)&buttons[i]);//释放中断 del_timer_sync(&buttons[i].timer);//删除一个定时器 } return -EBUSY; } ev_press = 1; return 0;}//按键关闭处理函数static int tiny4412_buttons_close(struct inode *inode, struct file *file){ int irq, i; for (i = 0; i < ARRAY_SIZE(buttons); i++) { if (!buttons[i].gpio) continue; //同样的，这里也是释放 irq = gpio_to_irq(buttons[i].gpio); free_irq(irq, (void *)&buttons[i]);<span style="white-space:pre"> </span>//删除一个定时器 del_timer_sync(&buttons[i].timer); } return 0;}//读取按键的键值函数static int tiny4412_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp){ unsigned long err; if (!ev_press) { if (filp->f_flags & O_NONBLOCK) return -EAGAIN; else //等待中断的事件产生 wait_event_interruptible(button_waitq, ev_press); } ev_press = 0; //将获取到的键值返回到用户空间 err = copy_to_user((void *)buff, (const void *)(&key_values), min(sizeof(key_values), count)); return err ? -EFAULT : min(sizeof(key_values), count);}//按键非阻塞型接口设计static unsigned int tiny4412_buttons_poll( struct file *file, struct poll_table_struct *wait){ unsigned int mask = 0;<span style="white-space:pre"> </span>//非阻塞型等待 poll_wait(file, &button_waitq, wait); if (ev_press) mask |= POLLIN | POLLRDNORM; return mask;}//驱动文件操作结构体成员初始化static struct file_operations dev_fops = { .owner = THIS_MODULE, .open = tiny4412_buttons_open, .release = tiny4412_buttons_close, .read = tiny4412_buttons_read, .poll = tiny4412_buttons_poll,};//注册杂类设备的结构体成员初始化static struct miscdevice misc = { .minor = MISC_DYNAMIC_MINOR, .name = DEVICE_NAME, .fops = &dev_fops, //这里就是把上面那个文件操作结构体的成员注册到杂类操作这里};//按键驱动初始化static int __init button_dev_init(void){ int ret; //先注册一个杂类设备 //这相当于让misc去管理open ,read,write,close这些接口 ret = misc_register(&misc); // printk(DEVICE_NAME"\tinitialized\n"); return ret;}//按键驱动注销static void __exit button_dev_exit(void){ //注销一个杂类设备驱动 misc_deregister(&misc);}module_init(button_dev_init);module_exit(button_dev_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("Yang.yuanxin");运行结果: