字符驱动模板－globalmem《Linux设备驱动开发详解》

liebo

/*======================================================================
    A globalmem driver as an example of char device drivers  
   
    The initial developer of the original code is Baohua Song
    . All Rights Reserved.
======================================================================*/
#include
#include
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#include
#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,0则为自动分配主设备号*/
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,globalmem字符设备的空间大小*/
  struct semaphore sem; /*并发控制使用的信用量*/        
};

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;/*globalmem_devp在初始化程序中设为对应的指针*/
  return 0;
  /*或者:(一个或多个设备的情况)
  struct globalmem_dev *dev_t;
  dev_t = container_of(inode->i_cdev,struct globalmem_dev,cdev);
  filp->private_data = dev_t;
  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:

      if(down_interruptible(&dev->sem)) /*获得信号量*/
      {
        return -ERESTARTSYS;
      }
      memset(dev->mem, 0, GLOBALMEM_SIZE);

      up(&dev->sem); /*释放信用量*/   
  
      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;

if(down_interruptible(&dev->sem)) /*获得信号量*/
    {
      return -ERESTARTSYS;
    }

  /*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);
  }

  up(&dev->sem); /*释放信号量*/

  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;
  
  if(down_interruptible(&dev->sem)) /*获得信号量*/
    {
      return -ERESTARTSYS;
    }
  
  /*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);
  }

  up(&dev->sem); /*释放信号量*/

  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  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) 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
  memset(globalmem_devp, 0, sizeof(struct globalmem_dev));
  
  globalmem_setup_cdev(globalmem_devp, 0);

  /*有n个设备时,可申请n个globalmem_dev空间,再初始化:*/
  /*globalmem_devp = kmalloc(n*sizeof(struct globalmem_dev), GFP_KERNEL);
  globalmem_setup_cdev(&globalmem_devp[0], 0);
  ......
  globalmem_setup_cdev(&globalmem_devp[n-1], n-1);  */

  init_MUTEX(&globalmem_devp->sem); /*初始化信号量*/
  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*/
  /*有n个设备时:
  cdev_del(&(globalmem_devp[0].cdev));  
  ......
  cdev_del(&(globalmem_devp[n-1].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);


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