Mini2440 按键驱动程序学习笔记

参考了友善之臂的按键驱动程序和韦东山写的《嵌入式Linux应用开发完全手册》一书的第20章—Linux异常处理体系结构部分的按键驱动程序，修改了部分内容，学习了嵌入式Linux下按键驱动程序。

按照习惯，先看原理，对所学习的知识结构有了大致的了解了开始阅读别人的代码，仔细分析代码实现的每个过程。由于时间有限，我只了解了一些概念性的理论和内核代码中部分数据结构，学习的过程还有待深入。对于我这样的初学者来说，想把资料中所介绍的每个原理和具体的实现方法都完全掌握，恐怕不止是时间的问题，我所追求的是一种快速上手的方法，先学会用再深入学习。

下面是经我改动后的按键驱动程序：

/*buttons_driver.c*/

 

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

     

#define DEVICE_NAME     "buttons"

     

      struct button_irq_desc {

             int irq;

             int pin;

             int pin_setting;

             int number;

             char *name;

      };

     

      static struct button_irq_desc button_irqs [] = {

             {IRQ_EINT8 , S3C2410_GPG0 ,  S3C2410_GPG0_EINT8  , 0, "KEY0"},

             {IRQ_EINT11, S3C2410_GPG3 ,  S3C2410_GPG3_EINT11 , 1, "KEY1"},

             {IRQ_EINT13, S3C2410_GPG5 ,  S3C2410_GPG5_EINT13 , 2, "KEY2"},

             {IRQ_EINT15, S3C2410_GPG7 ,  S3C2410_GPG7_EINT15 , 3, "KEY3"},

             {IRQ_EINT14, S3C2410_GPG6 ,  S3C2410_GPG6_EINT14 , 4, "KEY4"},

             {IRQ_EINT19, S3C2410_GPG11,  S3C2410_GPG11_EINT19, 5, "KEY5"},

      };

     

      static volatile char key_values [] = {'0', '0', '0', '0', '0', '0'};

     

      static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

     

      static volatile int ev_press = 0;

     

     

      static irqreturn_t buttons_interrupt(int irq, void *dev_id)

      {

             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);

            

             return IRQ_RETVAL(IRQ_HANDLED);

      }

     

     

      static int s3c24xx_buttons_open(struct inode *inode, struct file *file)

      {

             int i;

             int err;

             //set the interrupt to falling

       //友善的是上升沿和下降沿都中断，这里改成下降沿中断

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

                    err = request_irq(button_irqs[i].irq, buttons_interrupt, IRQ_TYPE_EDGE_FALLING,

                                                  button_irqs[i].name, (void *)&button_irqs[i]);

                    if (err)

                           break;

             }

     

             if (err) {

                    i--;

                    for (; i >= 0; i--) {

                    disable_irq(button_irqs[i].irq);

                           free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);

                    }

                    return -EBUSY;

             }

     

             ev_press = 1;

            

             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++) {

             free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);

             }

     

             return 0;

      }

     

     

      static int s3c24xx_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp)

      {

             unsigned long err;

     

             if (!ev_press) {

             if (filp->f_flags & O_NONBLOCK)

                    return -EAGAIN;

             else

                    wait_event_interruptible(button_waitq, ev_press);

             }

            

             ev_press = 0;

     

             err = copy_to_user(buff, (const void *)key_values, min(sizeof(key_values), count));

     

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

      }

 

      #if 0

      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)

                    mask |= POLLIN | POLLRDNORM;

             return mask;

      }

      #endif

     

      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,

             .name = DEVICE_NAME,

             .fops = &dev_fops,

      };

     

     

      static int __init dev_init(void)

      {

             int ret;

     

             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("MARK");

      MODULE_DESCRIPTION("Study S3C2440");

 

 

Makefile 文件如下：

obj-m:=buttons_driver.o

CURRENT_PATH:=$(shell pwd)

ARM_LINUX_KERNEL:=/opt/linux-2.6.29.1

all:

      $(MAKE) -C $(ARM_LINUX_KERNEL) SUBDIRS=$(CURRENT_PATH) modules

clean:

      rm -rf *.cmd *.o *.ko  *.mod.c *.symvers *.order

 

 

测试程序如下：

/*buttons_test.c*/

 

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

 

int main(void)

{

      int buttons_fd;

      char buttons[6] = {'0', '0', '0', '0', '0', '0'};

 

      buttons_fd = open("/dev/buttons", 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;

}

 

Makefile文件如下：

all:

      arm-linux-gcc buttons_test.c -o buttons_test

clean:

      rm -rf *.o buttons_test

 

总结一下：参考的资料是韦东山的《嵌入式Linux应用开发完全手册》，这本书我买了，感觉里面既将了入门的知识，也讲了需要一定基础才能掌握的知识，作为参考是本不错的书，虽然没有把每一步都完全讲出来，也不可能讲得那么详细。还有就是《Linux设备驱动程序(第三版)》，这本书我也买了，个人感觉很不错，LW写的书就是专业，讲的都是核心知识。还有就是《Linux设备驱动开发详解》，宋宝华编的，看过他的资料，从他写的书中可以看出他Linux方面非常专业，非常深入，有一股傲气，向他学习没错。

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