嵌入式

Mini2440 按键驱动程序学习笔记

2019-07-13 01:44发布

站内文章 / 嵌入式Linux
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 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" initialized ");                   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.oCURRENT_PATH:=$(shell pwd)ARM_LINUX_KERNEL:=/opt/linux-2.6.29.1all:      $(MAKE) -C $(ARM_LINUX_KERNEL) SUBDIRS=$(CURRENT_PATH) modulesclean:      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! ",i+1);                    }             }                               }       close(buttons_fd);      return 0;} Makefile文件如下：all:      arm-linux-gcc buttons_test.c -o buttons_testclean:      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。很想买这本书，可惜暂时没Money(可怜的人啊)，等过一段时间一定买一本。

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