这两天一直在看字符驱动那块，后来从网上找啦几个例子，自己编译啦下，安装啥的都挺正常，就是用测试程序测试的时候总出问题，现在找到一个能测试的代码，自己先看看和原来的那个代码有啥不同，后面会继续更新，说下到底是啥问题导致驱动不能用。先附上能用代码的链接，这里先谢谢作者：
http://blog.chinaunix.net/uid-22666248-id-3052861.html
#include <linux/kernel.h> #include <linux/module.h> #include <linux/init.h> #include <linux/cdev.h> #include <linux/device.h> #include <linux/slab.h>//kmalloc #include <linux/vmalloc.h>//vmalloc() #include <linux/types.h>//ssize_t #include <linux/fs.h>//file_operaiotns #include <linux/uaccess.h>//copy_from_user #define MEM_MALLOC_SIZE 4096 ////缓冲区大小 #define MEM_MAJOR 240 ////主设备号 #define MEM_MINOR 0 char *mem_spvm = NULL; ////缓冲区指针，指向内存区 struct cdev *mem_cdev = NULL; //字符设备对象指针 struct class *mem_class = NULL; //设备类指针 static int __init mem_init(void); static void __exit mem_exit(void); static int mem_open(struct inode *inode,struct file *filp); static int mem_release(struct inode *inode, struct file *filp); static ssize_t mem_read(struct file *filp,char __user *buf,size_t count,loff_t *fpos); static ssize_t mem_write(struct file *filp, char __user *buf,size_t count ,loff_t *fops); static const struct file_operations mem_fops={ .owner = THIS_MODULE, .open = mem_open, .release = mem_release, .read = mem_read, .write = mem_write, }; static int __init mem_init(void) { int ret; //创建设备号 主次设备号 int devno = MKDEV(MEM_MAJOR,MEM_MINOR); printk("mem_init initial... "); //开辟内核内存缓冲区 mem_spvm = (char *)vmalloc(MEM_MALLOC_SIZE); if(mem_spvm == NULL) { printk("vmalloc mem_spvm error "); return -ENOMEM;// } // mem_cdev = cdev_alloc(); if(mem_cdev == NULL) { printk("cdev_alloc error "); return -ENOMEM; } cdev_init(mem_cdev,&mem_fops); mem_cdev->owner = THIS_MODULE; ret = cdev_add(mem_cdev,devno,1);//将字符设备键入内核系统 if(ret) { cdev_del(mem_cdev); mem_cdev = NULL; printk("cdev_add error "); return -1; } // mem_class = class_create(THIS_MODULE,"ywx_class_char"); if(IS_ERR(mem_class)) { printk("class_create error.. "); return -1; } device_create(mem_class,NULL,MKDEV(MEM_MAJOR,MEM_MINOR),NULL,"ywx_device_char"); printk("init finished.. "); return 0; } static void __exit mem_exit(void) { printk("mem_exit starting.. "); if(mem_cdev != NULL) cdev_del(mem_cdev); printk("cdev_del ok "); device_destroy(mem_class,MKDEV(MEM_MAJOR,MEM_MINOR)); class_destroy(mem_class); if(mem_spvm != NULL) vfree(mem_spvm); printk("vfree ok "); printk("mem_exit finished.. "); } static int mem_open(struct inode *inode,struct file *filp) { printk("open vmalloc space.. "); try_module_get(THIS_MODULE);//模块引用计数器自加 printk("open vamlloc space ok.. "); return 0; } static int mem_release(struct inode *inode, struct file *filp) { printk("close vmalloc space.. "); module_put(THIS_MODULE);//模块引用计数器自减 return 0; } static ssize_t mem_read(struct file *filp,char __user *buf,size_t count,loff_t *fpos) { int ret = -1; char *tmp; printk("copy data to the user space "); tmp = mem_spvm; if(count > MEM_MALLOC_SIZE) count = MEM_MALLOC_SIZE; if(tmp != NULL)//将内核数据写入到用户空间 ret = copy_to_user(buf,tmp,count); if(ret == 0) { printk("read copy data success "); return count; } else { printk("read copy data error "); return 0; } } static ssize_t mem_write(struct file *filp, char __user *buf,size_t count ,loff_t *fops) { int ret = -1; char *tmp; printk("read data from the user space. "); tmp = mem_spvm; if(count > MEM_MALLOC_SIZE) count = MEM_MALLOC_SIZE; if(tmp != NULL) ret = copy_from_user(tmp,buf,count); if(ret == 0) { printk("write copy data success. "); return count; } else { printk("write copy data error. "); return 0; } } MODULE_LICENSE("GPL"); module_init(mem_init); module_exit(mem_exit);
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h> #include <string.h>//memset() int main(int argc, char *argv[]) { int fd,cnt; char buf[256]; int i; printf("char device testing.. "); fd = open("/dev/ywx_device_char",O_RDWR); if(fd == 0) { printf("open failed. "); return 1; } printf("input the data for kernel:"); scanf("%s",buf); cnt = write(fd,buf,256); if(cnt == 0) printf("write error "); printf("clear buf,and will read from kernel... "); for(i=0;i<256;i++) buf[i] = 32;//32 =" " cnt = read(fd,buf,256); if(cnt > 0) printf("read data from kernel is:%s ",buf); else printf("read data error "); close(fd); printf("close app.. "); return 0; }
运行的时候用root用户运行，可以看到/dev目录下有设备节点，然后运行test文件，可以看到能运行。
make;sudo insmod xxx.ko; sudo ./app