注册字符类设备

分配内存空间函数　kmalloc 用于分配连续虚拟地址小内存分配，在linux/slab.h 头文件中
- 参数１　申请内存的大小最大128k
- 参数２　GFP_KERNEL 代表优先权，内存不够延迟分配

清空内存数据memset 　参数１　地址，参数２　起始地址，参数３　长度

字符设备初始化函数cdev_init
- 在头文件include/linux/cdev.h
- 参数１cdev 字符设备文件结构体
- 参数２　file_operation 结构体
- 注册设备本质是想linux 设备文件中添加数据，这些数据需要初始化

字符设备注册函数cdev_add
- 在头文件include/linux/cdev.h
- 参数１cdev 字符设备结构体
- 参数２设备号
- 参数３　设备范围大小
- 向系统注册设备也是想linux 系统添加数据

源码

#include 
   
    #include 
    
     //　定义module_param module_param_arrary 函数的头文件#include 
     
      // 定义参数函数中perm 参数的枚举量头文件#include 
      
       //　MKDEV 转换设备号数据类型的宏定义#include 
       
         // 三个字符设备号函数＃include 
        
         // 定义字符设备的结构体＃include 
         
          // 分配内存空间的函数#include 
          
           ＃defind DEVICE_NAME "dcdev";＃defind DEVICE_MINOR_NUM 2;＃defind DEVICE_MAJOR 0;// 主设备号＃defind DEVICE_MINOR 0;#defind REGDEV_SIZE 3000;module_init(sdev_init);module_exit(sdev_exit);static int module_arg1,module_arg2;static int int_array[50];static int int_num;int numdev_major = DEVICE_MAJOR;int numdev_minor = DEVICE_MINOR;/**/// 输入主设备号module_param(numdev_major,int,S_IRUSR);// 输入次设备号module_param(numdev_minor,int,S_IRUSR);struct reg_dev{ char* data; unsigned long size; struct cdev cdev;};struct file_operations my_fops = { .owner = THIS_MODULE,};static void ret_init_cdev(struct reg_dev * dev,int index){ int error; /*数据初始化*/ int devno = MKDEV(numdev_major,numdev_minor+index); cdev_init(&dev->cdev,&my_fops); dev->cdev.owner = THIS_MODULE; dev->cdev.ops = &my_fops; err = cdev_add(&dev->cdev,devno,1); if(err){ printk(KERN_EMERG,"\t cdev_add is fail err is %d \n ",err); }else{ printk(KERN_EMERG,"\t cdev_add success! \n" ); }}struct reg_dev* my_devices;static int sdev_init(void){ int ret = -1; dev_t num_dev; if(numdev_major){ // 如果０　则动态申请 num_dev = MKDEV(numdev_major,numdev_minor); ret = register_chrdev_region(num_dev,DEVICE_MINOR_NUM,DEVICE_NAME); }else{ ret = allo_chrdev_region(&num_dev,numdev_minor,DEVICE_MINOR_NUM,DEVICE_NAME); numdev_major = MAJOR(num_dev); printk(KERN_EMERG,"\t numdev_major %d is failed\n ",numdev_major); } if(!ret){ printk(KERN_EMERG,"\t register_chrdev_region req %d is failed\n ",numdev_major); } my_devices = kmalloc(DEVICE_MINOR_NUM*sizeof(struct reg_dev),GPF_KERNEL); if(!my_devices){ ret = -ENOMEM; goto fail; return 0; } /*初始化设备*/ for(int i = 0 ;i < DEVICE_MINOR_NUM;i++){ my_devices[i].data = kmalloc(REGDEV_SIZE,GFP_KERNEL); memset(my_devices[i].data,0,REGDEV_SIZE); /*设备注册到系统*/ ret_init_cdev(&my_devices[i],i); } memset(my_devices,0,DEVICE_MINOR_NUM * sizeof(struct reg_dev)); printk(KERN_EMERG,"\ dcdev enter!\n "); return 0;fail: /*注销设备号*/ unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM); printk(KERN_EMERG,"\kmalloc is fail!\n "); return 0;}static int sdev_exit(void){ int i = 0; printk(KERN_EMERG,"\t cdev is:%d\n ",module_arg２); /*除去字符设备*/ for(i = 0;i < DEVICE_MINOR_NUM;i++){ cdev_del(&(my_devices[i]->cdev)); } unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM); return 0;}