globalmem.ko --- 字符设备驱动

原创 于 2012-06-22 14:00:18 发布 · 439 阅读 · 1 ·
CC 4.0 BY-SA版权
版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。
文章标签：

#struct #module #file #user #function #cmd

本文详细介绍了如何使用Linux内核开发全球内存驱动作为字符设备的实例，包括设备结构体定义、文件操作函数实现及模块加载卸载过程。

摘要生成于 C知道 ，由 DeepSeek-R1 满血版支持， 前往体验 >

/*======================================================================

    A globalmem driver as an example of char device drivers  
    The initial developer of the original code is Baohua Song
    <author@linuxdriver.cn>. All Rights Reserved.
======================================================================*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>

#define GLOBALMEM_SIZE 0x1000    /*全局内存最大4K字节*/
#define MEM_CLEAR 0x1  /*清0全局内存*/
#define GLOBALMEM_MAJOR 254    /*预设的globalmem的主设备号*/

static int globalmem_major = GLOBALMEM_MAJOR;

/*globalmem设备结构体*/
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)
{
  /*将设备结构体指针赋值给文件私有数据指针*/
  filp->private_data = globalmem_devp;
  return 0;
}

/*文件释放函数*/
int globalmem_release(struct inode *inode, struct file *filp)
{
  return 0;
}

/* ioctl设备控制函数 */
static int 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*/
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*/

  /*分析和获取有效的写长度*/
  if (p >= GLOBALMEM_SIZE)
    return count ?  - ENXIO: 0;
  if (count > GLOBALMEM_SIZE - p)
    count = GLOBALMEM_SIZE - p;

  /*内核空间->用户空间*/
  if (copy_to_user(buf, (void*)(dev->mem + p), count))
  {
    ret =  - EFAULT;
  }
  else
  {
    *ppos += count;
    ret = count;

    printk(KERN_INFO "read %d bytes(s) from %d\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; /*获得设备结构体指针*/

  /*分析和获取有效的写长度*/
  if (p >= GLOBALMEM_SIZE)
    return count ?  - ENXIO: 0;
  if (count > GLOBALMEM_SIZE - p)
    count = GLOBALMEM_SIZE - p;

  /*用户空间->内核空间*/
  if (copy_from_user(dev->mem + p, buf, count))
    ret =  - EFAULT;
  else
  {
    *ppos += count;
    ret = count;
    printk(KERN_INFO "written %d bytes(s) from %d\n", count, p);
  }
  return ret;
}

/* seek文件定位函数 */
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,
  .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*/
int globalmem_init(void)
{
  int result;
  dev_t devno = MKDEV(globalmem_major, 0);

  /* 申请设备号*/
  if (globalmem_major)
    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;

  /* 动态申请设备结构体的内存*/
  globalmem_devp = kmalloc(sizeof(struct globalmem_dev), GFP_KERNEL);
  if (!globalmem_devp)    /*申请失败*/
  {
    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*/
void 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);


[root@localhost globalmem]# cat Makefile

KERNELDIR ?= /lib/modules/2.6.18-92.el5xen/build/

PWD := $(shell pwd)

obj-m := globalmem.o

default:

        $(MAKE) -C $(KERNELDIR) M=$(PWD) modules

[root@localhost globalmem]# make

make -C /lib/modules/2.6.18-92.el5xen/build/ M=/home/xxha/songbaohua/6/globalmem modules

make[1]: Entering directory `/usr/src/kernels/2.6.18-92.el5-xen-i686'

  CC [M]  /home/xxha/songbaohua/6/globalmem/globalmem.o

/home/xxha/songbaohua/6/globalmem/globalmem.c: In function ‘globalmem_read’:

/home/xxha/songbaohua/6/globalmem/globalmem.c:89:警告：格式‘%d’需要类型‘int’，但实参 3的类型为‘long unsigned int’

/home/xxha/songbaohua/6/globalmem/globalmem.c: In function ‘globalmem_write’:

/home/xxha/songbaohua/6/globalmem/globalmem.c:118:警告：格式‘%d’需要类型‘int’，但实参 3的类型为‘long unsigned int’

  Building modules, stage 2.

  MODPOST

  CC      /home/xxha/songbaohua/6/globalmem/globalmem.mod.o

  LD [M]  /home/xxha/songbaohua/6/globalmem/globalmem.ko

make[1]: Leaving directory `/usr/src/kernels/2.6.18-92.el5-xen-i686'

[root@localhost globalmem]#

 

Insmod 时产生错误：

xiyoulinux@xiyoulinux-desktop:~/lsaism/globalmem$ sudo insmod globalmem.ko

insmod: error inserting 'globalmem.ko': -1 Device or resource busy

可能原因：主设备号冲突；

删掉静态申请，直接用动态申请,通过：

   //if(globalmem_major) 
        // result = register_chrdev_region(devno,1,"globalmem"); 
  // else 
       //  { 
          result = alloc_chrdev_region(&devno,0,1,"globalmem");       
          globalmem_major = MAJOR(devno); 
       //}


 xiyoulinux@xiyoulinux-desktop:~/lsaism/globalmem$ insmod globalmem.ko

xiyoulinux@xiyoulinux-desktop:~/lsaism/globalmem$

 

xiyoulinux@xiyoulinux-desktop:/$ echo 'hello' > /dev/globalmem

bash: /dev/globalmem: Permission denied

 写：

给globalmem文件x属性；

xiyoulinux@xiyoulinux-desktop:~/lsaism/globalmem$ chmod 777 /dev/globalmem

xiyoulinux@xiyoulinux-desktop:~/lsaism/globalmem$ echo 'hello' >/dev/globalmem

xiyoulinux@xiyoulinux-desktop:~/lsaism/globalmem$

 

读：

xiyoulinux@xiyoulinux-desktop:~/lsaism/globalmem$ cat /dev/globalmem

hello

 

由于globalmem字符驱动程序带有一个参数就是globalmem_major，就是指定主设备号的，程序中默认的是254，但在ubuntu系统上，254已经被占用，所以才会出现插入时出错，这时可以在插入时指定主设备号：

 insmod globalmem.ko globalmem_major=251

评论
添加红包

请填写红包祝福语或标题

个

红包个数最小为10个

元

红包金额最低5元

当前余额3.43元 前往充值 >
需支付：10.00元
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付元
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明：

1.余额是钱包充值的虚拟货币，按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载，可以购买VIP、付费专栏及课程。

余额充值