按键驱动程序设计笔记

<p>/*本来友善的程序是检测上升沿和下降沿的，
当按下按键，输出  KEY？ down
当弹下按键，输出  KEY？ up   

现在修改成只检测下降沿按下的
*/



#include <linux/module.h>/*模块有关的*/
#include <linux/kernel.h>/*内核有关的*/
#include <linux/fs.h>/*文件系统有关的*/
#include <linux/init.h>/*init*/
#include <linux/delay.h> /*delay*/
#include <linux/poll.h>/*poll*/
#include <linux/irq.h>/*中断*/
#include <asm/irq.h>/*中断*/
#include <linux/interrupt.h>/*linux中断*/
#include <asm/uaccess.h>/*uaccess*/
#include <mach/regs-gpio.h> /*寄存器设置*/
#include <mach/hardware.h>/*hardware*/
#include <linux/platform_device.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
#include <linux/sched.h>
#include <linux/gpio.h>

#define DEVICE_NAME     "button"



struct button_irq_desc {
    int irq;/*中断号*/
    int pin;/*中断控制的寄存器*/
    int pin_setting; /*中断的引脚*/
    int number;/*按键编号*/
    char *name;/*按键名称*/
};

static struct button_irq_desc button_irqs [] = {
    {IRQ_EINT8 , S3C2410_GPG(0) ,  S3C2410_GPG0_EINT8  , 0, "KEY0"},
    {IRQ_EINT11, S3C2410_GPG(3) ,  S3C2410_GPG3_EINT11 , 1, "KEY1"},
    {IRQ_EINT13, S3C2410_GPG(5) ,  S3C2410_GPG5_EINT13 , 2, "KEY2"},
    {IRQ_EINT14, S3C2410_GPG(6) ,  S3C2410_GPG6_EINT14 , 3, "KEY3"},
    {IRQ_EINT15, S3C2410_GPG(7) ,  S3C2410_GPG7_EINT15 , 4, "KEY4"},
    {IRQ_EINT19, S3C2410_GPG(11),  S3C2410_GPG11_EINT19, 5, "KEY5"},
};
/*存放按键操作结果*/
static volatile char key_values [] = {'0', '0', '0', '0', '0', '0'};
/*创建一个等待队列*/
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
/*按键标志位*/
static volatile int ev_press = 0;


static irqreturn_t buttons_interrupt(int irq, void *dev_id)
{
/*这里注意*/
    struct button_irq_desc *button_irqs = (struct button_irq_desc *)dev_id;
  
	if ('0'== key_values[button_irqs->number]) { // Changed

      

		key_values[button_irqs->number] =  '1';

    }

	else if('1' == key_values[button_irqs->number]){

		key_values[button_irqs->number] = '0';

	}
	ev_press = 1;
    wake_up_interruptible(&button_waitq);//有数据可读，唤醒读进程
    
    return IRQ_RETVAL(IRQ_HANDLED);
}


static int s3c24xx_buttons_open(struct inode *inode, struct file *file)
{
    int i;
    int err = 0;
    
    for (i = 0; i < sizeof(button_irqs)/sizeof(button_irqs[0]); i++) 
   {
	if (button_irqs[i].irq < 0)
	{
		continue;
	}
	/*
	int request_irq(unsigned int irq, void (*handler)(int, void*, struct pt_regs *), unsigned long flags, const char *devname, void *dev_id)

	返回0表示成功，或者返回一个错误码

	参数：
	irq：中断号
	handler：中断处理函数
	flags：与中断管理有关的各种选项
	devname：设备名
	dev_id：共享中断时使用

	不同中断号注册同一中断处理函数buttons_interrupt
	
	IRQ_TYPE_EDGE_BOTH (IRQ_TYPE_EDGE_FALLING | IRQ_TYPE_EDGE_RISING)
	上升沿或者下降沿产生中断

	(void *)&button_irqs[i]   把结构体数组变量地址给void *dev_id
	

	*/
        err = request_irq(button_irqs[i].irq, buttons_interrupt, IRQ_TYPE_EDGE_RISING, 
                          button_irqs[i].name, (void *)&button_irqs[i]);
        if (err)
            break;
    }

    if (err) {
        i--;
        for (; i >= 0; i--) {
	    if (button_irqs[i].irq < 0) {
		continue;
	    }
	    disable_irq(button_irqs[i].irq);
            free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);
        }
        return -EBUSY;
    }

    ev_press = 1;//按下
    
    return 0;
}


static int s3c24xx_buttons_close(struct inode *inode, struct file *file)
{
    int i;
    
    for (i = 0; i < sizeof(button_irqs)/sizeof(button_irqs[0]); i++) {
	if (button_irqs[i].irq < 0) {
	    continue;
	}
	free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);
    }

    return 0;
}

/*read函数读取key_values数组的结果*/
/*由它读取键盘输入的结果*/
/*实质上就是读取key_values数组的值*/
/*它完成了键盘作为输入设备的核心功能*/
/*数组是否可读,要根据标志位ev_press来判断*/
/*如果数组可读,则读取数据到用户buffer中*/
/*如果数组不可读,则读进程进入等待队列,等待到数组可读为止*/
/*等待队列机制,是中断管理中常用到的机制*/
/*因为有些进程经常需要等待某一事件的发生*/

static int s3c24xx_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp)
{
    unsigned long err;

		
    if (!ev_press) {//没按下时
    /*看看用户有没有要求不阻塞*/
		if (filp->f_flags & O_NONBLOCK)
			return -EAGAIN;
		else
			/*阻塞在button_waitq  等待队列上*/
			/*此时没数据可读，让读进程阻塞掉*/
			wait_event_interruptible(button_waitq, ev_press);//ev_press=1时，返回
    }
    //这时是ev_press = 1
    ev_press = 0;
/*把键值读到用户*/
    err = copy_to_user(buff, (const void *)key_values, min(sizeof(key_values), count));

    return err ? -EFAULT : min(sizeof(key_values), count);
}

static unsigned int s3c24xx_buttons_poll( struct file *file, struct poll_table_struct *wait)
{
    unsigned int mask = 0;
    poll_wait(file, &button_waitq, wait);
    if (ev_press)//为1的时候按键按下
        mask |= POLLIN | POLLRDNORM;
    return mask;
}


static struct file_operations dev_fops = {
    .owner   =   THIS_MODULE,
    .open    =   s3c24xx_buttons_open,
    .release =   s3c24xx_buttons_close, 
    .read    =   s3c24xx_buttons_read,
    .poll    =   s3c24xx_buttons_poll,
};

static struct miscdevice misc = {
	.minor = MISC_DYNAMIC_MINOR,//动态次设备号
	.name = DEVICE_NAME,
	.fops = &dev_fops,//关联文件操作
};

static int __init dev_init(void)
{
	int ret;
/*混杂设备注册*/
	ret = misc_register(&misc);

	printk (DEVICE_NAME"\tinitialized\n");

	return ret;
}

static void __exit dev_exit(void)
{
	misc_deregister(&misc);
}

module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Bai");
</p>
<p>
</p>测试程序：<pre name="code" class="cpp">#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/time.h>
#include <errno.h>
 
int main(void)
{
      int buttons_fd;
      char buttons[6] = {'0', '0', '0', '0', '0', '0'};
      buttons_fd = open("/dev/button", 0);

      if (buttons_fd < 0) {
             perror("open device buttons");

             exit(1);
      }

      for (;;) {
             char current_buttons[6];
             int i;

             if (read(buttons_fd, current_buttons, sizeof current_buttons) != sizeof current_buttons) {
                    perror("read buttons:");
                    exit(1);

             }
             for (i = 0; i < sizeof buttons / sizeof buttons[0]; i++) {

                    if (buttons[i] != current_buttons[i]) {

                           buttons[i] = current_buttons[i];

                           printf("The %d key is pressed!\n",i+1);

                    }

             }                    
      }

      close(buttons_fd);
      return 0;

}
</pre>

1.中断处理函数

static irqreturn_t buttons_interrupt(int irq, void *dev_id)；

每次按键触发中断，进入中断处理函数，进行相关操作。

中断资源弥足珍贵，最好选择在打开设备即需要使用时注册，而不是装载模块时，若退出模块时请切记释放中断资源。

2.工作队列

static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

创建了一个等待队列，每当有一按键按下，激活队列中一个等待的任务。

poll_wait(file, &button_waitq, wait);
监测进程队列button_waitq里的进程，如果ev_press置1，就跳出等待。

wait_event_interruptible(button_waitq, ev_press);
等待，当ev_press为1时，跳出。

wake_up_interruptible(&button_waitq);

数组可读，唤醒休眠的进程。

当加进udelay(20000);消抖动时，出现错误，没网上，有空再搞搞

insmodbutton.ko

button:Unknownsymbol__bad_udelay

insmod:cannotinsert'button.ko':unknownsymbolinmoduleorinvalidparamete