linux中嵌入式开发完整代码驱动与应用程序交互示例代码--实验测试通过

#include <linux/init.h> #include <linux/module.h> #include <linux/fs.h> #include <linux/device.h> #include <linux/uaccess.h> /*声明设备文件操作的打开、读写、关闭基本操作*/ /*定义这些函数与file_operations中的函数指针相对应*/ ssize_t chr_drv_read(struct file *filep, char __user *buffer, size_t sizet, loff_t *lofft);//从设备中同步读取数据 ssize_t chr_drv_write(struct file *filep, const char __user *buffer, size_t sizet, loff_t *lofft);//向设备发送数据 int chr_drv_open(struct inode *inodep, struct file *filep); //打开 int chr_drv_close(struct inode *inodep, struct file *filep); //关闭 struct device *dev; struct class *devclass; static unsigned int dev_major = 270;//指静态指定设备号为280 //user instructions "cat /proc/devices" to view all devices and devices major const struct file_operations my_fops={ //文件io接口结构体,以实现open //read，write的操作 .open = chr_drv_open, /*把函数chr_drv_open赋值给指定.open*/ /*使用用户的程序open与设备驱动的open关联起来，用 .open 实现关联*/ .read = chr_drv_read, /*把函数chr_drv_read赋值给指定.read*/ .write = chr_drv_write, /*把函数chr_drv_write赋值给指定.write*/ .release = chr_drv_close, /*把函数chr_drv_close赋值给指定.close*/ /*关闭驱动文件*/ }; static int kernel_val =555; //read(fd,buffer,count); /*设备文件的打开、读写、关闭*/ ssize_t chr_drv_read(struct file *filep,char __user *buffer,size_t sizet,loff_t *lofft) { int ret; printk("-------------------%s---------------------\n",__FUNCTION__); ret=copy_to_user(buffer,&kernel_val,4);//kernel give data to user if(ret > 0){ printk("\nKERNEL: read failed.\n"); return -EFAULT; } return 0; } //write(fd,buf,count); ssize_t chr_drv_write(struct file *filep, const char __user *buffer, size_t sizet, loff_t *lofft) { int value; int ret; //printk("-------------------%s---------------------\n",__FUNCTION__); ret=copy_from_user(&value,buffer,4); if(ret > 0){ printk("\nwrite to KERNEL failed.\n"); return -EFAULT; } printk("\nI am KERNEL: value=%d\n",value); return 0; } int chr_drv_open(struct inode *inmodep, struct file *filep) { printk("-------------------%s---------------------\n",__FUNCTION__); return 0; } int chr_drv_close(struct inode *inodep, struct file *filep) { printk("-------------------%s---------------------\n",__FUNCTION__); return 0; } static int __init chr_drv_init(void) { #if 1 int ret;//设备号的返回值 //静态申请设备号 ret=register_chrdev(dev_major,"chr_drv_test",&my_fops); if(ret == 0){//设备号申请成功，返回值为0 printk("register successful.\n"); //mknod /dev/chr0 c dev_major 0; } else { printk("register fauled.\n"); return -EFAULT; //申请失败，返回错误码，错误码为一个负数 //或者写成 return -EINVAL } #endif #if 2 //自动创建设备节点 devclass = class_create(THIS_MODULE,"chrar2_dev"); dev = device_create(devclass,NULL,MKDEV(dev_major,0),NULL,"char2");//第３个参数 MKDEV(dev_major,0) //表示主设备号由 dev_major　指定，次设备号为0, 宏 //MKDEV　在目录\include\uapi\linux中定义的头文件 kdev_t.h 中指定 printk("auto create the nod successful.\n"); #endif return 0; } static void __exit chr_drv_exit(void) { #if 2//销毁动态创建的设备号 device_destroy(devclass,MKDEV(dev_major,0));//先销毁由 //device_create创建的设备 class_destroy(devclass);//再销毁由class_create函数创建的类 printk("device delet successful.\n"); #endif #if 1 //销毁静态创建的设备号 unregister_chrdev(dev_major,"chr_drv_test"); /*在模块卸载时释放设备号*/ printk("device delet successful.\n"); #endif } module_init(chr_drv_init); module_exit(chr_drv_exit); MODULE_LICENSE("GPL");