ubantu14.04第三个使用文件私有数据的globalmem的设备驱动

1. 代码如下：

#include <linux/init.h>#include <linux/module.h>#include <linux/types.h>#include <linux/mm.h>#include <linux/fs.h>#include <linux/errno.h>#include <linux/sched.h>#include <linux/cdev.h>#include <asm/io.h>//#include <asm/system.h>  //找不到这个文件#include <linux/slab.h> // for kmalloc and kfree function#include <asm/uaccess.h>#define GLOBALMEM_SIZE 0X1000 /*全局内存最大4KB*/#define MEM_CLEAR 0x1 /*清零全局内存*/#define GLOBALMEM_MAJOR 354static int globalmem_major = GLOBALMEM_MAJOR;/*预设的globalmem的主设备号*//*globalmem的设备结构体：包含了对应于globalmem字符设备的cdev 和 使用内存mem[GLOBALMEM_SIZE]*/struct globalmem_dev{struct cdev cdev;  //cdev结构体unsigned char mem[GLOBALMEM_SIZE];  //全局内存};struct globalmem_dev *globalmem_devp;  //设备结构体指针/*文件打开函数*/int globalmem_open(struct inode *inode,struct file *filp){filp->private_data = globalmem_devp; //将设备结构体指针赋值给文件私有数据指针return 0;}/*文件释放函数*/int globalmem_release(struct inode *inode,struct file *filp){return 0;}/*设备控制函数：ioctl()函数接受的MEM_CLEAR命令，这个命令将全局内存的有效数据长度清零，对于设备不支持的命令，ioctl()函数应该返回-EINVAL*/static long globalmem_ioctl( /*struct inode *inodep,*/struct file *filp,unsigned int cmd,unsigned long arg){ struct globalmem_dev *dev = filp->private_data; //获得设备结构体指针 switch(cmd) {  case  MEM_CLEAR:memset(dev->mem,0,GLOBALMEM_SIZE);printk(KERN_INFO"globalmem is set to zero\n");   break;  default:   return -EINVAL; } return 0;}/*读函数：读写函数主要是让设备结构体的mem[]数组与用户空间交互数据，并随着访问字节数变更返回用户的文件读写偏移位置*/static ssize_t globalmem_read(struct file *filp,char __user *buf,size_t size,loff_t *ppos ){ unsigned long p = *ppos; unsigned int count = size; int ret = 0; struct globalmem_dev *dev = filp->private_data; //获得设备结构体指针  if(p >= GLOBALMEM_SIZE)  //分析和获取有效的写长度 {  return count ? -ENXIO:0; } if(count > GLOBALMEM_SIZE - p) {  count = GLOBALMEM_SIZE - p; }  if(copy_to_user(buf,(void *)(dev->mem+p),count))  //内核空间->用户空间 {  ret = -EFAULT; } else {  *ppos += count;  ret = count;  printk(KERN_INFO"read %d bytes(s) from %ld\n",count,p); } return ret;}/*写函数*/static ssize_t globalmem_write(struct file *filp,const char __user *buf,size_t size,loff_t *ppos){ unsigned long p = *ppos; unsigned int count = size; int ret = 0;  struct globalmem_dev *dev = filp->private_data;  if(p >= GLOBALMEM_SIZE)  //分析和获取有效的写长度 {  return count? -ENXIO:0; }  if(count > GLOBALMEM_SIZE - p) {  count = GLOBALMEM_SIZE - p; }  if(copy_from_user(dev->mem + p,buf,count)) // 用户空间->内核空间 {  ret = -EFAULT; } else {  *ppos =+ count;  ret = count;  printk(KERN_INFO"written %d bytes(s) from %ld\n",count,p); } return ret;}/*seek文件定位函数：seek()函数对文件定位的起始地址可以是文件开头(SEEK_SET,0)、当前位置(SEEK_CUR,1)、文件尾(SEEK_END,2)*/static loff_t globalmem_llseek(struct file *filp,loff_t offset,int orig){ loff_t ret = 0; switch(orig) {  case 0:   //相对文件开始位置偏移   if(offset <0 )   {    ret = -EINVAL;    break;   }      if((unsigned int )offset > GLOBALMEM_SIZE)   {    ret = - EINVAL;    break;   }   filp->f_pos = (unsigned int)offset;   ret = filp->f_pos;   break;     case 1:   //相对文件当前位置偏移   if((filp->f_pos + offset) > GLOBALMEM_SIZE)   {    ret = -EINVAL;    break;   }   if((filp->f_pos + offset)<0)   {    ret = -EINVAL;    break;   }   filp->f_pos +=offset;   ret = filp->f_pos;   break;  default:   ret = -EINVAL;   break;  } return ret;}/*文件操作结构体*/static const struct file_operations globalmem_fops={ .owner = THIS_MODULE, .llseek = globalmem_llseek, .read = globalmem_read, .write = globalmem_write,// .ioctl = globalmem_ioctl, .unlocked_ioctl = globalmem_ioctl, .open = globalmem_open, .release = globalmem_release,};/*初始化并注册cdev*/static void globalmem_setup_cdev(struct globalmem_dev *dev,int index){ int err,devno = MKDEV(globalmem_major,index); cdev_init(&dev->cdev,&globalmem_fops); dev->cdev.owner = THIS_MODULE; dev->cdev.ops = &globalmem_fops; err = cdev_add(&dev->cdev,devno,1); if(err) {  printk(KERN_NOTICE"Error %d adding LED%d",err,index); } }/*设备驱动模块加载函数*/static int __init globalmem_init(void){ int result; dev_t devno = MKDEV(globalmem_major,0);  if(globalmem_major) //申请设备号 {  result = register_chrdev_region(devno,1,"globalmem"); } else  //动态申请设备号 {  result = alloc_chrdev_region(&devno,0,1,"globalmem");  globalmem_major = MAJOR(devno); }  if(result < 0) {  return result; }  globalmem_devp = kmalloc(sizeof(struct globalmem_dev),GFP_KERNEL); //申请设备结构体的内存 if(!globalmem_devp) {  result = -ENOMEM;  goto fail_malloc; }  memset(globalmem_devp,0,sizeof(struct globalmem_dev)); globalmem_setup_cdev(globalmem_devp,0); return 0;  fail_malloc:unregister_chrdev_region(devno,1); return result;}/*模块卸载函数*/static void __exit globalmem_exit(void){ cdev_del(&globalmem_devp->cdev); //注销cdev kfree(globalmem_devp);          //释放设备结构体内存 unregister_chrdev_region(MKDEV(globalmem_major,0),1); //释放设备号}MODULE_AUTHOR("Song Baohua");MODULE_LICENSE("Dual BSD/GPL");module_param(globalmem_major,int,S_IRUGO);module_init(globalmem_init);module_exit(globalmem_exit);

2. Makefile:

</pre><p></p><pre name="code" class="plain">KERNELDIR := /lib/modules/$(shell uname -r)/build obj-m := globalmem.omodules:$(MAKE) -C $(KERNELDIR) M=$(PWD) modulesmodules_install:$(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install  clean:make -C $(KERNELDIR) M=`pwd` modules clean  rm -rf modules.order  

3. 执行：make ,然后sudo insmod globalmem.ko;

4.

 验证：lsmod 可以看到该模块，mknod /dev/globalmem c 354 0, echo 'good nihao' > /dev/globalmem, cat /dev/globalmem可以看到输出good nihao;

还出现了：cat: /dev/globalmem: 没有那个设备或地址，目前不知道是什么问题；

代码验证：

#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>#include <stdlib.h>void main(void){int fd;int i;char data[256];int retval;fd = open("/dev/globalmem",O_RDWR);if(fd==-1){perror("erroropen\n");exit(-1);}printf("open/dev/globalmem successfully\n");//写数据retval = write(fd,"mem",3);if(retval==-1){perror("writeerror\n");exit(-1);}printf("write successfully\n");close(fd);      //若不重新打开，则globalmem.c中的write函数写入后，其写位置*ppos更新了,所以导致下面的读将从写入后的位置        // 开始读，从而导致读不到数据，如写入后，*ppos位置为9，下次读时将从位置9开始读，导致读不到数据，当然可以设置为

       // 从文件开始位置读，如：copy_to_user(buf, dev->mem, count)        fd = open("/dev/globalmem",O_RDWR); //  重新打开后，globalmem.c中的read和write函数中的读写位置都是为0        if(fd==-1)  // <span style="color:#ff0000;">上面不关闭也行，使用lseek( fd, 0L, SEEK_SET );就可以了</span>        {                perror("erroropen\n");                   exit(-1);        }//读数据retval=read(fd,data,3 );if(retval==-1){perror("readerror\n");exit(-1);}data[retval]=0;printf("read successfully:%s\n",data);//关闭设备close(fd);}

输出如下：

open/dev/globalmem successfully
write successfully
read successfully:mem