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今天看了韦东山视频第12课第8节讲的是字符设备驱动程序之定时器防抖动，该视频详细的讲解了按键防抖动的原理：当你按一次按健时，由于按健有反应时间、有抖动，可能你按一次机器感应到几次，防抖就是让在按键正常反应时间内机器只感应一次按键效果，防止误操作。当按键发生时产生中断，在中断服务程序中修改一个定时器的定时时间为10ms,并从10ms开始重新计数。定时器时间到后产生定时器中断，按键处理放在定时器中断里面。这样当10ms内有多个中断发生时只有最后一个中断起作用，以达到消除抖动的目的。
韦东山视频讲得非常好， 一、开发环境 •主 机：VMWare--Fedora 9 •Kernel：linux-2.6.32.2 •编译器：arm-linux-gcc-4.3.2 二、参考驱动程序 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include struct cdev cdev; #include static struct class *sixthdrv_class; //volatile unsigned long *gpfcon; //volatile unsigned long *gpfdat; static struct timer_list buttons_timer; static DECLARE_WAIT_QUEUE_HEAD(button_waitq); /* 中断事件标志, 中断服务程序将它置1，sixth_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 0x05, 0x06 */ /* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 0x85, 0x86*/ static unsigned char key_val; struct pin_desc pins_desc[6] = { {S3C2410_GPG(0), 0x01}, {S3C2410_GPG(3), 0x02}, {S3C2410_GPG(5), 0x03}, {S3C2410_GPG(6), 0x04}, {S3C2410_GPG(7), 0x05}, {S3C2410_GPG(11),0x06}, }; static struct pin_desc *irq_pd; //static atomic_t canopen = ATOMIC_INIT(1); //定义原子变量并初始化为1 static DECLARE_MUTEX(button_lock); //定义互斥锁 static irqreturn_t buttons_irq(int irq, void *dev_id) { /* 发生中断20ms后启动定时器 */ irq_pd = (struct pin_desc *)dev_id; mod_timer(&buttons_timer, jiffies+HZ/50); return IRQ_RETVAL(IRQ_HANDLED); } static int sixth_drv_open(struct inode *inode, struct file *file) { #if 0 if (!atomic_dec_and_test(&canopen)) { atomic_inc(&canopen); return -EBUSY; } #endif if (file->f_flags & O_NONBLOCK) { if (down_trylock(&button_lock)) return -EBUSY; } else { /* 获取信号量 */ down(&button_lock); } /* 设置GPG0,3,5,6,7,11为中断引脚 ,寄存器与中断引脚的联结*/ s3c2410_gpio_cfgpin(S3C2410_GPG(0),S3C2410_GPG0_EINT8); s3c2410_gpio_cfgpin(S3C2410_GPG(3),S3C2410_GPG3_EINT11); s3c2410_gpio_cfgpin(S3C2410_GPG(5),S3C2410_GPG5_EINT13); s3c2410_gpio_cfgpin(S3C2410_GPG(6),S3C2410_GPG6_EINT14); s3c2410_gpio_cfgpin(S3C2410_GPG(7),S3C2410_GPG7_EINT15); s3c2410_gpio_cfgpin(S3C2410_GPG(11),S3C2410_GPG11_EINT19); /*中断的注册*/ request_irq(IRQ_EINT8, buttons_irq, IRQF_DISABLED, "S1", &pins_desc[0]); request_irq(IRQ_EINT11, buttons_irq, IRQF_DISABLED, "S2", &pins_desc[1]); request_irq(IRQ_EINT13, buttons_irq, IRQF_DISABLED, "S3", &pins_desc[2]); request_irq(IRQ_EINT14, buttons_irq, IRQF_DISABLED, "S4", &pins_desc[3]); request_irq(IRQ_EINT15, buttons_irq, IRQF_DISABLED, "S5", &pins_desc[4]); request_irq(IRQ_EINT19, buttons_irq, IRQF_DISABLED, "S6", &pins_desc[5]); /*中断类型的设置，为双边缘触发*/ set_irq_type(IRQ_EINT8,IRQ_TYPE_EDGE_BOTH); set_irq_type(IRQ_EINT11,IRQ_TYPE_EDGE_BOTH); set_irq_type(IRQ_EINT13,IRQ_TYPE_EDGE_BOTH); set_irq_type(IRQ_EINT14,IRQ_TYPE_EDGE_BOTH); set_irq_type(IRQ_EINT15,IRQ_TYPE_EDGE_BOTH); set_irq_type(IRQ_EINT19,IRQ_TYPE_EDGE_BOTH); return 0; } ssize_t sixth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) { if (size != 1) return -EINVAL; if (file->f_flags & O_NONBLOCK) { if (!ev_press) return -EAGAIN; } else { /* 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 sixth_drv_close(struct inode *inode, struct file *file) { //atomic_inc(&canopen); free_irq(IRQ_EINT8, &pins_desc[0]); free_irq(IRQ_EINT11, &pins_desc[1]); free_irq(IRQ_EINT13, &pins_desc[2]); free_irq(IRQ_EINT14, &pins_desc[3]); free_irq(IRQ_EINT15, &pins_desc[4]); free_irq(IRQ_EINT19, &pins_desc[5]); up(&button_lock); return 0; } static unsigned sixth_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 sixth_drv_fasync (int fd, struct file *filp, int on) { printk("driver: sixth_drv_fasyncn"); return fasync_helper (fd, filp, on, &button_async); } static struct file_operations sixth_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 = sixth_drv_open, .read = sixth_drv_read, .release = sixth_drv_close, .poll = sixth_drv_poll, .fasync = sixth_drv_fasync, }; /* * 确定按键值 */ static void buttons_timer_function(unsigned long data) { struct pin_desc * pindesc = irq_pd; unsigned int pinval; if (!pindesc) return; 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); } int major; static int sixth_drv_init(void) { int result; dev_t devno = MKDEV(major, 0); /* 静态申请设备号*/ if (major) result = register_chrdev_region(devno, 1, "sixth_drv_new"); else /* 动态分配设备号 */ { result = alloc_chrdev_region(&devno, 0, 1, "sixth_drv_new"); major = MAJOR(devno); } if (result < 0) return result; /*初始化cdev结构*/ cdev_init(&cdev, &sixth_drv_fops); cdev.owner = THIS_MODULE; cdev.ops = &sixth_drv_fops; /* 注册字符设备 */ cdev_add(&cdev, MKDEV(major, 0), 1); sixthdrv_class = class_create(THIS_MODULE, "sixth_drv"); device_create(sixthdrv_class, NULL, MKDEV(major,0), NULL, "buttons"); /* /dev/buttons */ init_timer(&buttons_timer); buttons_timer.function = buttons_timer_function; //buttons_timer.expires = 0; add_timer(&buttons_timer); // gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16); // gpfdat = gpfcon + 1; return 0; } static void sixth_drv_exit(void) { cdev_del(&cdev); /*注销设备*/ unregister_chrdev_region(MKDEV(major, 0), 1); /*释放设备号*/ device_destroy(sixthdrv_class,MKDEV(major,0)); //释放设备文件 class_destroy(sixthdrv_class);//释放设备类 // iounmap(gpfcon); //return 0; } module_init(sixth_drv_init); module_exit(sixth_drv_exit); MODULE_LICENSE("GPL"); 
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