实现的功能是在读取按键信息的时候,如果没有产生按键,则程序休眠在read函数中,利用poll机制,可以在没有退出的情况下让程序自动退出。
下面的程序就是在读取按键信息的时候,如果5000ms内没有按键信息,则自己退出。
首先应用程序执行poll函数
kernel中的sys_poll
do_sys_poll
init_poll_funcptr-->do_poll
do_poll
for(;;)
{
if(do_pollfd(pfd,pt))
{
count++; //如果驱动的poll返回非0值,那么count++
//把进程挂到队列中休眠
pt=null;}
if( count || !*timeout || signal_pending(current))
break; //如果count非0 超时, 有信号等待处理
}
__timeout = schedule_timeout(__time_out); //休眠 下次执行到上面的判断时,就会超时退出
驱动代码:
#include <linux/sched.h> #include <linux/signal.h> #include <linux/spinlock.h> #include <linux/errno.h> #include <linux/random.h> #include <linux/poll.h> #include <linux/init.h> #include <linux/slab.h> #include <linux/module.h> #include <linux/wait.h> #include <linux/mutex.h> #include <linux/io.h> #include <asm/irq.h> #include <linux/irq.h> #include <linux/fs.h> #include <asm/arch/regs-gpio.h> #include <linux/interrupt.h> #include <linux/poll.h> static struct class *key_class; //创建类 static struct class_device *key_class_devs; //创建类对应的设备 struct pin_desc{ unsigned int pin; unsigned int key_val; }; struct pin_desc pins_desc[4] = { {S3C2410_GPF0,0X01}, {S3C2410_GPF2,0X02}, {S3C2410_GPG3,0X03}, {S3C2410_GPG11,0X04}, }; unsigned char keyvals=0; static volatile int ev_press = 0; static DECLARE_WAIT_QUEUE_HEAD(button_waitq); static irqreturn_t keys_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) { keyvals = pindesc->key_val|0x80; } else { keyvals = pindesc->key_val; } ev_press = 1; wake_up_interruptible(&button_waitq); return IRQ_HANDLED; } int key_open(struct inode *inode, struct file *fp) { request_irq( IRQ_EINT0, keys_irq, IRQT_BOTHEDGE, "key2", &pins_desc[0]); request_irq( IRQ_EINT2, keys_irq, IRQT_BOTHEDGE, "key3", &pins_desc[1]); request_irq( IRQ_EINT11, keys_irq, IRQT_BOTHEDGE, "key4", &pins_desc[2]); request_irq( IRQ_EINT19, keys_irq, IRQT_BOTHEDGE, "key5", &pins_desc[3]); return 0; } ssize_t key_read(struct file *fp, char __user *buff, size_t count, loff_t *offp){ if(count != 1) { return -EINVAL; } wait_event_interruptible(button_waitq,ev_press); copy_to_user(buff,&keyvals,1); ev_press = 0; return 0; } ssize_t key_write(struct file *fp, const char __user *buf, size_t count, loff_t *ppos){ } int key_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]); } static unsigned int key_poll(struct file *file, struct poll_table_struct *wait) { unsigned int mask = 0; poll_wait(file, &button_waitq,wait); if(ev_press) mask |= POLLIN|POLLRDNORM; return mask; } struct file_operations led_fops={ .owner = THIS_MODULE, .open = key_open, .write = key_write, .read = key_read, .release = key_close, .poll = key_poll, }; int major; static int key_init(void) { major = register_chrdev( 0,"key_drv", &led_fops ); key_class = class_create(THIS_MODULE,"key_class"); key_class_devs = class_device_create(key_class,NULL,MKDEV(major,0),NULL,"my_keys"); printk("key install Module "); return 0; } static void key_exit(void) { unregister_chrdev( major, "key_drv" ); class_device_unregister(key_class_devs); class_destroy(key_class); printk("key Module exit "); } module_init(key_init); module_exit(key_exit); MODULE_LICENSE("GPL");
应用测试代码:
#include <stdio.h> #include <fcntl.h> #include <poll.h> int main() { int fd; int ret; struct pollfd pfd[1]; unsigned char key_val; fd = open("/dev/my_keys",O_RDWR); if(fd<0) { printf("open failed "); return 0; } pfd[0].fd = fd; pfd[0].events = POLLIN; while(1) { ret = poll(pfd, 1, 5000); //如果在5000ms之内没有按下按键 这自动退出 // read(fd, &key_val,1); if(ret==0) printf("time out "); else { read(fd, &key_val,1); printf("key:%x ",key_val); } } }
sd