Linux字符设备驱动学习1

最新推荐文章于 2025-03-04 22:12:25 发布

木稻

最新推荐文章于 2025-03-04 22:12:25 发布

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分类专栏：嵌入式

本文链接：https://blog.youkuaiyun.com/u013445716/article/details/41726841

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本文介绍了一个基于Linux的按键驱动程序实现细节，包括初始化、中断处理、读取操作等关键部分。通过对GPIO配置、中断请求及处理流程的讲解，展示了如何在嵌入式系统中实现按键功能。

#include #include #include #include #include #include #include #include #include #include #include static struct class *thirddrv_class;static struct class_device *thirddrv_class_dev;volatile unsigned long *gpfcon;volatile unsigned long *gpfdat;volatile unsigned long *gpgcon;volatile unsigned long *gpgdat;static DECLARE_WAIT_QUEUE_HEAD(button_waitq);/* 中断事件标志, 中断服务程序将它置1，third_drv_read将它清0 */static volatile int ev_press = 0;struct pin_desc{unsigned int pin;unsigned int key_val;};/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 *//* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */static unsigned char key_val;struct pin_desc pins_desc[4] = {{S3C2410_GPF0, 0x01},{S3C2410_GPF2, 0x02},{S3C2410_GPG3, 0x03},{S3C2410_GPG11, 0x04},};/* * 确定按键值 */static irqreturn_t buttons_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){/* 松开 */key_val = 0x80 | pindesc->key_val;}else{/* 按下 */key_val = pindesc->key_val;} ev_press = 1; /* 表示中断发生了 */ wake_up_interruptible(&button_waitq); /* 唤醒休眠的进程 */return IRQ_RETVAL(IRQ_HANDLED);}static int third_drv_open(struct inode *inode, struct file *file){/* 配置GPF0,2为输入引脚 *//* 配置GPG3,11为输入引脚 *///原型int request_irq(unsigned int irq, void (*handler)(int irq, void *dev_id, struct pt_regs *regs ), unsigned long irqflags, const char * devname, void *dev_id);request_irq(IRQ_EINT0, buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);request_irq(IRQ_EINT2, buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);return 0;}ssize_t third_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos){if (size != 1)return -EINVAL;/* 如果没有按键动作, 休眠 */wait_event_interruptible(button_waitq, ev_press);/* 如果有按键动作, 返回键值 */copy_to_user(buf, &key_val, 1);ev_press = 0;return 1;}int third_drv_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]);return 0;}static struct file_operations sencod_drv_fops = { .owner = THIS_MODULE, /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */ .open = third_drv_open, .read = third_drv_read, .release = third_drv_close, };int major;static int third_drv_init(void){major = register_chrdev(0, "third_drv", &sencod_drv_fops);thirddrv_class = class_create(THIS_MODULE, "third_drv");thirddrv_class_dev = class_device_create(thirddrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);gpfdat = gpfcon + 1;gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);gpgdat = gpgcon + 1;return 0;}static void third_drv_exit(void){unregister_chrdev(major, "third_drv");class_device_unregister(thirddrv_class_dev);class_destroy(thirddrv_class);iounmap(gpfcon);iounmap(gpgcon);return 0;}module_init(third_drv_init);module_exit(third_drv_exit);MODULE_LICENSE("GPL");