驱动程序

#include <linux/init.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/gpio.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/timer.h>struct device_node *dnode;
struct gpio_desc *gpiono1;
struct gpio_desc *gpiono2;
struct gpio_desc *gpiono3;struct cdev *cdev;
char kbuf[128] = {0};
//主设备号
unsigned int major = 0;
//次设备号
unsigned int minor = 0;
//设备号
dev_t devno;
module_param(major,uint,0664);  //方便在命令行传递major的值
//用于保存目录信息
struct class *cls;
//用于保存设备节点信息
struct device *dev;int mycdev_open(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);return 0;
}ssize_t mycdev_write(struct file *file, const char  *ubuf, size_t size, loff_t *lof)
{unsigned long ret;//从用户空间读取数据if(size>sizeof(kbuf))//用户空间期待读取的大小内核满足不了，那就给内核支持的最大大小size=sizeof(kbuf);ret=copy_from_user(kbuf,ubuf,size);if(ret)//拷贝失败{printk("copy_to_user filed\n");return ret;}switch(kbuf[0]){case '1'://LED1if(kbuf[1]=='0')//关灯gpiod_set_value(gpiono1,0);else//开灯gpiod_set_value(gpiono1,1);break;case '2'://LED2if(kbuf[1]=='0')//关灯gpiod_set_value(gpiono2,0);else//开灯gpiod_set_value(gpiono2,1);break;case '3'://LED3if(kbuf[1]=='0')//关灯gpiod_set_value(gpiono3,0);else//开灯gpiod_set_value(gpiono3,1);break;}return 0;
}int mycdev_close(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);return 0;
}//定义操作方法结构体变量并赋值
struct file_operations fops={.open=mycdev_open,.write=mycdev_write,.release=mycdev_close,
};static int __init mycdev_init(void)
{//解析LED设备树节点dnode = of_find_node_by_path("/myled");if(dnode == NULL){printk("解析设备树节点失败\n");return -ENXIO;}printk("解析GPIO信息成功\n");//申请GPIO对象gpiono1 = gpiod_get_from_of_node(dnode,"led1-gpio",0,GPIOD_OUT_LOW,NULL);if(IS_ERR(gpiono1)){printk("申请gpio1对象失败\n");return -ENXIO;}printk("申请gpio1信息对象成功\n");//申请GPIO对象gpiono2 = gpiod_get_from_of_node(dnode,"led2-gpio",0,GPIOD_OUT_LOW,NULL);if(IS_ERR(gpiono2)){printk("申请gpio2对象失败\n");return -ENXIO;}printk("申请gpio2信息对象成功\n");//申请GPIO对象gpiono3 = gpiod_get_from_of_node(dnode,"led3-gpio",0,GPIOD_OUT_LOW,NULL);if(IS_ERR(gpiono3)){printk("申请gpio3对象失败\n");return -ENXIO;}printk("申请gpio3信息对象成功\n");int ret;// 为字符设备驱动对象申请空间cdev = cdev_alloc();if (cdev == NULL){printk("字符设备驱动对象申请空间失败\n");ret = -EFAULT;goto out1;}printk("申请对象空间成功\n");// 初始化字符设备驱动对象cdev_init(cdev, &fops);// 申请设备号if (major > 0) // 静态指定设备号{ret = register_chrdev_region(MKDEV(major, minor), 3, "myled");if (ret){printk("静态申请设备号失败\n");goto out2;}}else if (major == 0) // 动态申请设备号{ret = alloc_chrdev_region(&devno, minor, 3, "myled");if (ret){printk("动态申请设备号失败\n");goto out2;}major = MAJOR(devno); // 获取主设备号minor = MINOR(devno); // 获取次设备号}printk("申请设备号成功\n");// 注册字符设备驱动对象ret = cdev_add(cdev, MKDEV(major, minor), 3);if (ret){printk("注册字符设备驱动对象失败\n");goto out3;}printk("注册字符设备驱动对象成功\n");// 向上提交目录信息cls = class_create(THIS_MODULE, "myled");if (IS_ERR(cls)){printk("向上提交目录失败\n");ret = -PTR_ERR(cls);goto out4;}printk("向上提交目录成功\n");// 向上提交设备节点信息int i;for (i = 0; i < 3; i++){dev = device_create(cls, NULL, MKDEV(major, i), NULL, "myled%d", i);if (IS_ERR(dev)){printk("向上提交设备节点信息失败\n");ret = -PTR_ERR(dev);goto out5;}}printk("向上提交设备信息成功\n");return 0;
out5:// 释放前一次提交成功的设备信息for (--i; i >= 0; i--){device_destroy(cls, MKDEV(major, i));}class_destroy(cls); // 释放目录
out4:cdev_del(cdev);
out3:unregister_chrdev_region(MKDEV(major, minor), 3);
out2:kfree(cdev);
out1:return ret;
}
static void __exit mycdev_exit(void)
{//灭灯gpiod_set_value(gpiono1,0);gpiod_set_value(gpiono2,0);gpiod_set_value(gpiono3,0);//释放gpio编号gpiod_put(gpiono1);gpiod_put(gpiono2);gpiod_put(gpiono3);// 释放节点信息int i;for (i = 0; i < 3; i++){device_destroy(cls, MKDEV(major, i));}// 销毁目录class_destroy(cls);// 注销驱动对象cdev_del(cdev);// 释放设备号unregister_chrdev_region(MKDEV(major, minor), 3);// 释放对象空间kfree(cdev);
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

应用程序

#include<stdlib.h>
#include<stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include<unistd.h>
#include<string.h>int main(int argc, char const *argv[])
{char buf[128]={0};int fd=open("/dev/myled0",O_RDWR);if(fd<0){printf("打开设备文件失败\n");exit(-1);}while(1){//从终端读取printf("请输入两个字符\n");printf("第一个字符:1(LED1) 2(LED2) 3(LED3)\n");printf("第二个字符:0(关灯) 1(开灯)\n");printf("请输入>");fgets(buf,sizeof(buf),stdin);buf[strlen(buf)-1]='\0';//向设备文件中写write(fd,buf,sizeof(buf));}close(fd);return 0;
}