Linux学习 ：按键信号 之 异步通知

一、异步通知概念：　　异步通知是指：一旦设备就绪，则主动通知应用程序，应用程序根本就不需要查询设备状态，类似于中断的概念，一个进程收到一个信号与处理器收到一个中断请求可以说是一样的。信号是异步的，一个进程不必通过任何操作来等待信号的到达。下面我们就看一下在linux中机制的实现方式。　　在linux中，异步通知是使用信号来实现的，而在linux，大概有30种信号，比如大家熟悉的ctrl+c的SIGINT信号，进程能够忽略或者捕获除过SIGSTOP和SIGKILL的全部信号，当信号背捕获以后，有相应的signal()函数来捕获信号，函数原型：sighandler_t signal(int signum, sighandler_t handler); 第一个参数就是指定的信号的值，而第二个参数便是此信号的信号处理函数，当为SIG_IGN,表示信号被忽略，当为SIG_DFL时，表示采用系统的默认方 式来处理该信号。当然，信号处理函数也可以自己定义。当signal()调用成功后，返回处理函数handler值，调用失败后返回SIG_ERR。 二、信号处理要点：①、注册信号处理函数：应用注册②、发送者：驱动drv③、接受者：应用app④、发送方法：kill_fasync (&button_async, SIGIO, POLL_IN); 三、 原子操作：执行过程中不会被别的代码路径所中断的操作常用原子操作函数：atomic_t v = ATOMIC_INIT(0); //定义原子变量v并初始化为0atomic_read(atomic_t *v);       //返回原子变量的值void atomic_inc(atomic_t *v);  //原子变量增加1void atomic_dec(atomic_t *v);  //原子变量减少1int atomic_dec_and_test(atomic_t *v);  //自减操作后测试结果，0返回真，否则返回假  四、信号量1.定义：struct semaphore sem:2.初始化：void sema_init(struct semaphore *sem, int val);　　　　　void init_MUTEX(stuct semaphore *sem); //初始化为0     static DECLARE_MUTEX(button_lock); //定义互斥锁3.获得信号量: void down(struct semaphore *sem);　　　　　　   int down_interruptible(struct semaphore *sem);　　　　　　　int down_trylock(struct semaphore *sem);4.释放信号量：　　　　　　 void up(struct semaphore *sem); 五、阻塞：执行设备操作时若不能获得资源，则挂起进入休眠状态，被从调度器的运行队列移走，直到条件满足。　　非阻塞：执行设备操作时若不能获得资源，释放或查询等待条件满足。　：　fd = open("/dev/buttons", O_RDWR | O_NONBLOCK);六、示例代码：1.驱动代码: signal_drv.c ========================================#include#include#include#include#include#include#include#include#include#include#include#includestatic struct class *signaldrv_class;static struct class_device*signaldrv_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，signal_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},};//static atomic_t canopen = ATOMIC_INIT(1); //定义原子变量并初始化为1static DECLARE_MUTEX(button_lock); //定义互斥锁/** 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 signal_drv_open(struct inode *inode, struct file *file){#if 0if (!atomic_dec_and_test(&canopen)){atomic_inc(&canopen);return -EBUSY;}#endifif (file->f_flags & O_NONBLOCK){if (down_trylock(&button_lock))return -EBUSY;}else{/* 获取信号量 */down(&button_lock);}/* 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 signal_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 signal_drv_close(struct inode *inode, struct file *file){//atomic_inc(&canopen);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]);up(&button_lock);return 0;}static unsigned signal_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 signal_drv_fasync (int fd, struct file *filp, int on){printk("driver: signal_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 = signal_drv_open,.read =signal_drv_read,.release = signal_drv_close,.poll = signal_drv_poll,.fasync = signal_drv_fasync,};int major;static int signal_drv_init(void){major = register_chrdev(0, "signal_drv", &sencod_drv_fops);signaldrv_class = class_create(THIS_MODULE, "signal_drv");signaldrv_class_dev = class_device_create(signaldrv_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 signal_drv_exit(void){unregister_chrdev(major, "signal_drv");class_device_unregister(signaldrv_class_dev);class_destroy(signaldrv_class);iounmap(gpfcon);iounmap(gpgcon);return 0;}module_init(signal_drv_init);module_exit(signal_drv_exit);MODULE_LICENSE("GPL"); 2.测试代码：signaltest.c =============================================#include#include#include#include#include#include#include#include#include/* sixthdrvtest*/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 | O_NONBLOCK);if (fd{printf("can't open!\n");return -1;}//fcntl(fd, F_SETOWN, getpid());//Oflags = fcntl(fd, F_GETFL);//fcntl(fd, F_SETFL, Oflags | FASYNC);while (1){ret = read(fd, &key_val, 1);printf("key_val: 0x%x, ret = %d\n", key_val, ret);sleep(5);}return 0;} 3.Makefile: ================================KERN_DIR = /work/system/linux-2.6.22.6all:make -C $(KERN_DIR) M=`pwd` modulesclean:make -C $(KERN_DIR) M=`pwd` modules cleanrm -rf modules.orderobj-m+= signal_drv.orm -rf modules.order obj-m+= signal_drv.o