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》【下载见http://www.linuxidc.com/Linux/2011-01/31114.htm】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;