linux驱动之按键驱动

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目的：编写按键驱动

原理图：

按键与引脚对应关系：

1、编写驱动程序框架

2、查看原理图与s3c2440手册

3、编写open函数

配置引脚

4、编写read函数功能

驱动代码：

#include <linux/init.h>#include <linux/module.h>#include <linux/kernel.h>#include <linux/fs.h>#include <asm/io.h>#include <linux/cdev.h>#include <linux/device.h>#include <asm/uaccess.h>MODULE_LICENSE("Dual BSD/GPL");static struct class *buttondrv_class;static struct class_devices *buttondrv_class_dev;volatile unsigned long *gpfcon = NULL;volatile unsigned long *gpfdat = NULL;static int button_dev_open(struct inode *inode ,struct file* file){//配置按键的引脚 GPF0,1,2,4为输入引脚*gpfcon &= ~((0x3<<0*2)|(0x3<<1*2)|(0x3<<2*2)|(0x3<<4*2));return 0;}ssize_t button_dev_read(struct file *file,char __user *buf,size_t size,loff_t *ppos){/*返回四个引脚的电平*/unsigned char key_vals[4];int regval;if(size !=sizeof(key_vals)){return -EINVAL;}regval = *gpfdat;/*读四个引脚的电平*/key_vals[0] = (regval &(1<<0))? 1 : 0;key_vals[1] = (regval &(1<<1))? 1 : 0;key_vals[2] = (regval &(1<<2))? 1 : 0;key_vals[3] = (regval &(1<<4))? 1 : 0;copy_to_user(buf,key_vals,sizeof(key_vals));return sizeof(key_vals);}static struct file_operations button_sdv_fops ={.owner = THIS_MODULE,.open  = button_dev_open,.read = button_dev_read,};int major;static int button_dev_init(void)//入口函数{major = register_chrdev(0,"button_drv",&button_sdv_fops);buttondrv_class = class_create(THIS_MODULE,"button_drv");if(IS_ERR(buttondrv_class))return PTR_ERR(buttondrv_class);buttondrv_class_dev= device_create(buttondrv_class,NULL,MKDEV(major,0),NULL,"wq_button");if(unlikely(IS_ERR(buttondrv_class_dev)))return PTR_ERR(buttondrv_class_dev);/*映射物理地址*/gpfcon = (volatile unsigned long *) ioremap(0x56000050 ,16);gpfdat = gpfcon + 1;return 0;}static void button_dev_exit(void){unregister_chrdev(major,"button_drv");device_unregister(buttondrv_class_dev);class_destroy(buttondrv_class);iounmap(gpfcon);}module_init(button_dev_init);module_exit(button_dev_exit);

测试程序代码：

#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>/* * wq_device <dev> <on|off> */int main(int argc, char **argv){int cnt=0;int fd;unsigned char key_vals[4];fd = open("/dev/wq_button",O_RDWR);if(fd<0){printf("can't open \n");}while(1){read(fd,key_vals,sizeof(key_vals));if(!key_vals[0]||!key_vals[1]||!key_vals[2]||!key_vals[3]){printf("%04d k1 k2 k3 k4  is %d %d %d %d \n",cnt++,key_vals[0],key_vals[1],key_vals[2],key_vals[3]);}}return 0;}

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