• 嵌入式Linux驱动学习之路(十二)按键驱动-poll机制


    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

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  • 原文地址:https://www.cnblogs.com/ynxf/p/5999930.html
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