/*======================================================================    A globalmem driver as an example of char device drivers    There are two same globalmems in this driver      This example is to introduce the function of file->private_data        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	/*全局內(nèi)存最大4K字節(jié)*/#define MEM_CLEAR 0x1  /*清0全局內(nèi)存*/#define GLOBALMEM_MAJOR 254    /*預(yù)設(shè)的globalmem的主設(shè)備號(hào)*/static int globalmem_major = GLOBALMEM_MAJOR;/*globalmem設(shè)備結(jié)構(gòu)體*/struct globalmem_dev                                     {                                                          struct cdev cdev; /*cdev結(jié)構(gòu)體*/                         unsigned char mem[GLOBALMEM_SIZE]; /*全局內(nèi)存*/        };struct globalmem_dev *globalmem_devp; /*設(shè)備結(jié)構(gòu)體指針*//*文件打開函數(shù)*/int globalmem_open(struct inode *inode, struct file *filp){  /*將設(shè)備結(jié)構(gòu)體指針賦值給文件私有數(shù)據(jù)指針*/  struct globalmem_dev *dev;    dev = container_of(inode->i_cdev,struct globalmem_dev,cdev);    filp->private_data = dev;    return 0;}/*文件釋放函數(shù)*/int globalmem_release(struct inode *inode, struct file *filp){  return 0;}/* ioctl設(shè)備控制函數(shù) */static int globalmem_ioctl(struct inode *inodep, struct file *filp, unsigned  int cmd, unsigned long arg){  struct globalmem_dev *dev = filp->private_data;/*獲得設(shè)備結(jié)構(gòu)體指針*/  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;}/*讀函數(shù)*/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; /*獲得設(shè)備結(jié)構(gòu)體指針*/  /*分析和獲取有效的寫長(zhǎng)度*/  if (p >= GLOBALMEM_SIZE)    return count ?  - ENXIO: 0;  if (count > GLOBALMEM_SIZE - p)    count = GLOBALMEM_SIZE - p;  /*內(nèi)核空間->用戶空間*/  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;}/*寫函數(shù)*/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; /*獲得設(shè)備結(jié)構(gòu)體指針*/    /*分析和獲取有效的寫長(zhǎng)度*/  if (p >= GLOBALMEM_SIZE)    return count ?  - ENXIO: 0;  if (count > GLOBALMEM_SIZE - p)    count = GLOBALMEM_SIZE - p;      /*用戶空間->內(nèi)核空間*/  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文件定位函數(shù) */static loff_t globalmem_llseek(struct file *filp, loff_t offset, int orig){  loff_t ret = 0;  switch (orig)  {    case 0:   /*相對(duì)文件開始位置偏移*/      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:   /*相對(duì)文件當(dāng)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;}/*文件操作結(jié)構(gòu)體*/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,};/*初始化并注冊(cè)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);}/*設(shè)備驅(qū)動(dòng)模塊加載函數(shù)*/int globalmem_init(void){  int result;  dev_t devno = MKDEV(globalmem_major, 0);  /* 申請(qǐng)?jiān)O(shè)備號(hào)*/  if (globalmem_major)    result = register_chrdev_region(devno, 2, "globalmem");  else  /* 動(dòng)態(tài)申請(qǐng)?jiān)O(shè)備號(hào) */  {    result = alloc_chrdev_region(&devno, 0, 2, "globalmem");    globalmem_major = MAJOR(devno);  }    if (result < 0)    return result;      /* 動(dòng)態(tài)申請(qǐng)2個(gè)設(shè)備結(jié)構(gòu)體的內(nèi)存*/  globalmem_devp = kmalloc(2*sizeof(struct globalmem_dev), GFP_KERNEL);  if (!globalmem_devp)    /*申請(qǐng)失敗*/  {    result =  - ENOMEM;    goto fail_malloc;  }  memset(globalmem_devp, 0, 2*sizeof(struct globalmem_dev));    globalmem_setup_cdev(&globalmem_devp[0], 0);  globalmem_setup_cdev(&globalmem_devp[1], 1);  return 0;  fail_malloc: unregister_chrdev_region(devno, 2);  return result;}/*模塊卸載函數(shù)*/void globalmem_exit(void){  cdev_del(&(globalmem_devp[0].cdev));     cdev_del(&(globalmem_devp[1].cdev));   /*注銷cdev*/  kfree(globalmem_devp);     /*釋放設(shè)備結(jié)構(gòu)體內(nèi)存*/  unregister_chrdev_region(MKDEV(globalmem_major, 0), 2); /*釋放設(shè)備號(hào)*/}MODULE_AUTHOR("Song Baohua");MODULE_LICENSE("Dual BSD/GPL");module_param(globalmem_major, int, S_IRUGO);module_init(globalmem_init);module_exit(globalmem_exit);