linux字符类驱动示例

/*包含初始化宏定义的头文件,代码中的module_init和module_exit在此文件中*/#include <linux/init.h>/*包含初始化加载模块的头文件,代码中的MODULE_LICENSE在此头文件中*/#include <linux/module.h>/*定义module_param module_param_array的头文件*/#include <linux/moduleparam.h>/*定义module_param module_param_array中perm的头文件*/#include <linux/stat.h>/*三个字符设备函数*/#include <linux/fs.h>/*MKDEV转换设备号数据类型的宏定义*/#include <linux/kdev_t.h>/*定义字符设备的结构体*/#include <linux/cdev.h>/*分配内存空间函数头文件*/#include <linux/slab.h>/*包含函数device_create 结构体class等头文件*/#include <linux/device.h>#define DEVICE_NAME "chardevnode"#define DEVICE_MINOR_NUM 2#define DEV_MAJOR 0#define DEV_MINOR 0#define REGDEV_SIZE 3000MODULE_LICENSE("Dual BSD/GPL");/*声明是开源的，没有内核版本限制*/MODULE_AUTHOR("iTOPEET_dz");/*声明作者*/int numdev_major = DEV_MAJOR;int numdev_minor = DEV_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);static struct class *myclass;struct reg_dev{    char *data;    unsigned long size;    struct cdev cdev;};struct reg_dev *my_devices;/*打开操作*/static int chardevnode_open(struct inode *inode, struct file *file){    printk(KERN_EMERG "chardevnode_open is success!\n");    return 0;}/*关闭操作*/static int chardevnode_release(struct inode *inode, struct file *file){    printk(KERN_EMERG "chardevnode_release is success!\n");    return 0;}/*IO操作*/static long chardevnode_ioctl(struct file *file, unsigned int cmd, unsigned long arg){    printk(KERN_EMERG "chardevnode_ioctl is success! cmd is %d,arg is %d \n",cmd,arg);    return 0;}ssize_t chardevnode_read(struct file *file, char __user *buf, size_t count, loff_t *f_ops){    return 0;}ssize_t chardevnode_write(struct file *file, const char __user *buf, size_t count, loff_t *f_ops){    return 0;}loff_t chardevnode_llseek(struct file *file, loff_t offset, int ence){    return 0;}struct file_operations my_fops = {    .owner = THIS_MODULE,    .open = chardevnode_open,    .release = chardevnode_release,    .unlocked_ioctl = chardevnode_ioctl,    .read = chardevnode_read,    .write = chardevnode_write,    .llseek = chardevnode_llseek,};/*设备注册到系统*/static void reg_init_cdev(struct reg_dev *dev,int index){    int err;    int devno = MKDEV(numdev_major,numdev_minor+index);    /*数据初始化*/    cdev_init(&dev->cdev,&my_fops);    dev->cdev.owner = THIS_MODULE;    dev->cdev.ops = &my_fops;    /*注册到系统*/    err = cdev_add(&dev->cdev,devno,1);    if(err){        printk(KERN_EMERG "cdev_add %d is fail! %d\n",index,err);    }    else{        printk(KERN_EMERG "cdev_add %d is success!\n",numdev_minor+index);    }}static int scdev_init(void){    int ret = 0,i;    dev_t num_dev;    printk(KERN_EMERG "numdev_major is %d!\n",numdev_major);    printk(KERN_EMERG "numdev_minor is %d!\n",numdev_minor);    if(numdev_major){        num_dev = MKDEV(numdev_major,numdev_minor);        ret = register_chrdev_region(num_dev,DEVICE_MINOR_NUM,DEVICE_NAME);    }    else{        /*动态注册设备号*/        ret = alloc_chrdev_region(&num_dev,numdev_minor,DEVICE_MINOR_NUM,DEVICE_NAME);        /*获得主设备号*/        numdev_major = MAJOR(num_dev);        printk(KERN_EMERG "adev_region req %d !\n",numdev_major);    }    if(ret<0){        printk(KERN_EMERG "register_chrdev_region req %d is failed!\n",numdev_major);           }    myclass = class_create(THIS_MODULE,DEVICE_NAME);    my_devices = kmalloc(DEVICE_MINOR_NUM * sizeof(struct reg_dev),GFP_KERNEL);    if(!my_devices){        ret = -ENOMEM;        goto fail;    }    memset(my_devices,0,DEVICE_MINOR_NUM * sizeof(struct reg_dev));    /*设备初始化*/    for(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*/        reg_init_cdev(&my_devices[i],i);        /*创建设备节点*/        device_create(myclass,NULL,MKDEV(numdev_major,numdev_minor+i),NULL,DEVICE_NAME"%d",i);    }    printk(KERN_EMERG "scdev_init!\n");    /*打印信息，KERN_EMERG表示紧急信息*/    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 ret;}static void scdev_exit(void){    int i;    printk(KERN_EMERG "scdev_exit!\n");    /*除去字符设备*/    for(i=0;i<DEVICE_MINOR_NUM;i++){        cdev_del(&(my_devices[i].cdev));        /*摧毁设备节点函数d*/        device_destroy(myclass,MKDEV(numdev_major,numdev_minor+i));    }    /*释放设备class*/    class_destroy(myclass);    /*释放内存*/    kfree(my_devices);    unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);}module_init(scdev_init);/*初始化函数*/module_exit(scdev_exit);/*卸载函数*/