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分类: LINUX

2010-09-05 15:35:18

                     memdev.c
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include "memdev.h"
static mem_major = MEMDEV_MAJOR;
module_param(mem_major, int, S_IRUGO);
struct mem_dev *mem_devp; /*设备结构体指针*/
struct cdev cdev;
/*文件打开函数*/
int mem_open(struct inode *inode, struct file *filp)
{
    struct mem_dev *dev;
   
    /*获取次设备号*/
    int num = MINOR(inode->i_rdev);
    if (num >= MEMDEV_NR_DEVS)
            return -ENODEV;
    dev = &mem_devp[num];
   
    /*将设备描述结构指针赋值给文件私有数据指针*/
    filp->private_data = dev;
   
    return 0;
}
/*文件释放函数*/
int mem_release(struct inode *inode, struct file *filp)
{
  return 0;
}
/*读函数*/
static ssize_t mem_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 mem_dev *dev = filp->private_data; /*获得设备结构体指针*/
  /*判断读位置是否有效*/
  if (p >= MEMDEV_SIZE)
    return 0;
  if (count > MEMDEV_SIZE - p)
    count = MEMDEV_SIZE - p;
  /*读数据到用户空间*/
  if (copy_to_user(buf, (void*)(dev->data + 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 mem_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 mem_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 >= MEMDEV_SIZE)
    return 0;
  if (count > MEMDEV_SIZE - p)
    count = MEMDEV_SIZE - p;
   
  /*从用户空间写入数据*/
  if (copy_from_user(dev->data + 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 mem_llseek(struct file *filp, loff_t offset, int whence)
{
    loff_t newpos;
    switch(whence) {
      case 0: /* SEEK_SET */
        newpos = offset;
        break;
      case 1: /* SEEK_CUR */
        newpos = filp->f_pos + offset;
        break;
      case 2: /* SEEK_END */
        newpos = MEMDEV_SIZE -1 + offset;
        break;
      default: /* can't happen */
        return -EINVAL;
    }
    if ((newpos<0) || (newpos>MEMDEV_SIZE))
     return -EINVAL;
     
    filp->f_pos = newpos;
    return newpos;
}
/*文件操作结构体*/
static const struct file_operations mem_fops =
{
  .owner = THIS_MODULE,
  .llseek = mem_llseek,
  .read = mem_read,
  .write = mem_write,
  .open = mem_open,
  .release = mem_release,
};
/*设备驱动模块加载函数*/
static int memdev_init(void)
{
  int result;
  int i;
  dev_t devno = MKDEV(mem_major, 0);
  /* 静态申请设备号*/
  if (mem_major)
    result = register_chrdev_region(devno, 2, "memdev");
  else  /* 动态分配设备号 */
  {
    result = alloc_chrdev_region(&devno, 0, 2, "memdev");
    mem_major = MAJOR(devno);
  } 
 
  if (result < 0)
    return result;
  /*初始化cdev结构*/
  cdev_init(&cdev, &mem_fops);
  cdev.owner = THIS_MODULE;
  cdev.ops = &mem_fops;
 
  /* 注册字符设备 */
  cdev_add(&cdev, MKDEV(mem_major, 0), MEMDEV_NR_DEVS);
  
  /* 为设备描述结构分配内存*/
  mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev), GFP_KERNEL);
  if (!mem_devp)    /*申请失败*/
  {
    result =  - ENOMEM;
    goto fail_malloc;
  }
  memset(mem_devp, 0, sizeof(struct mem_dev));
 
  /*为设备分配内存*/
  for (i=0; i < MEMDEV_NR_DEVS; i++)
  {
        mem_devp[i].size = MEMDEV_SIZE;
        mem_devp[i].data = kmalloc(MEMDEV_SIZE, GFP_KERNEL);
        memset(mem_devp[i].data, 0, MEMDEV_SIZE);
  }
   
  return 0;
  fail_malloc:
  unregister_chrdev_region(devno, 1);
 
  return result;
}
/*模块卸载函数*/
static void memdev_exit(void)
{
  cdev_del(&cdev);   /*注销设备*/
  kfree(mem_devp);     /*释放设备结构体内存*/
  unregister_chrdev_region(MKDEV(mem_major, 0), 2); /*释放设备号*/
}
MODULE_AUTHOR("David Xie");
MODULE_LICENSE("GPL");
module_init(memdev_init);
module_exit(memdev_exit);
 
 
 
 
 
                  memdev.h

#ifndef _MEMDEV_H_
#define _MEMDEV_H_
#ifndef MEMDEV_MAJOR
#define MEMDEV_MAJOR 251   /*预设的mem的主设备号*/
#endif
#ifndef MEMDEV_NR_DEVS
#define MEMDEV_NR_DEVS 2    /*设备数*/
#endif
#ifndef MEMDEV_SIZE
#define MEMDEV_SIZE 4096
#endif
/*mem设备描述结构体*/
struct mem_dev                                    
{                                                       
  char *data;                     
  unsigned long size;      
};
#endif /* _MEMDEV_H_ */
 
 
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