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分类: 嵌入式

2011-01-18 21:42:02

  1. #ifndef _MEMDEV_H_
  2. #define _MEMDEV_H_

  3. #ifndef MEMDEV_MAJOR
  4. #define MEMDEV_MAJOR 0 /*预设的mem的主设备号*/
  5. #endif

  6. #ifndef MEMDEV_NR_DEVS
  7. #define MEMDEV_NR_DEVS 2 /*设备数*/
  8. #endif

  9. #ifndef MEMDEV_SIZE
  10. #define MEMDEV_SIZE 4096
  11. #endif

  12. /*mem设备描述结构体*/
  13. struct mem_dev
  14. {
  15.   char *data;
  16.   unsigned long size;
  17.   wait_queue_head_t inq;
  18. };

  19. #endif /* _MEMDEV_H_ */
  1. #include <linux/module.h>
  2. #include <linux/types.h>
  3. #include <linux/fs.h>
  4. #include <linux/errno.h>
  5. #include <linux/mm.h>
  6. #include <linux/sched.h>
  7. #include <linux/init.h>
  8. #include <linux/cdev.h>
  9. #include <asm/io.h>
  10. #include <asm/system.h>
  11. #include <asm/uaccess.h>

  12. #include <linux/poll.h>
  13. #include "memdev.h"

  14. static mem_major = MEMDEV_MAJOR;
  15. bool have_data = false; /*表明设备有足够数据可供读*/

  16. module_param(mem_major, int, S_IRUGO);

  17. struct mem_dev *mem_devp; /*设备结构体指针*/

  18. struct cdev cdev;

  19. /*文件打开函数*/
  20. int mem_open(struct inode *inode, struct file *filp)
  21. {
  22.     struct mem_dev *dev;
  23.     
  24.     /*获取次设备号*/
  25.     int num = MINOR(inode->i_rdev);

  26.     if (num >= MEMDEV_NR_DEVS)
  27.             return -ENODEV;
  28.     dev = &mem_devp[num];
  29.     
  30.     /*将设备描述结构指针赋值给文件私有数据指针*/
  31.     filp->private_data = dev;
  32.     
  33.     return 0;
  34. }

  35. /*文件释放函数*/
  36. int mem_release(struct inode *inode, struct file *filp)
  37. {
  38.   return 0;
  39. }

  40. /*读函数*/
  41. static ssize_t mem_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos)
  42. {
  43.   unsigned long p = *ppos;
  44.   unsigned int count = size;
  45.   int ret = 0;
  46.   struct mem_dev *dev = filp->private_data; /*获得设备结构体指针*/

  47.   /*判断读位置是否有效*/
  48.   if (p >= MEMDEV_SIZE)
  49.     return 0;
  50.   if (count > MEMDEV_SIZE - p)
  51.     count = MEMDEV_SIZE - p;
  52.     
  53.   while (!have_data) /* 没有数据可读,考虑为什么不用if,而用while */
  54.   {
  55.         if (filp->f_flags & O_NONBLOCK)
  56.             return -EAGAIN;
  57.     
  58.     wait_event_interruptible(dev->inq,have_data);
  59.   }

  60.   /*读数据到用户空间*/
  61.   if (copy_to_user(buf, (void*)(dev->data + p), count))
  62.   {
  63.     ret = - EFAULT;
  64.   }
  65.   else
  66.   {
  67.     *ppos += count;
  68.     ret = count;
  69.    
  70.     printk(KERN_INFO "read %d bytes(s) from %d\n", count, p);
  71.   }
  72.   
  73.   have_data = false; /* 表明不再有数据可读 */
  74.   /* 唤醒写进程 */
  75.   return ret;
  76. }

  77. /*写函数*/
  78. static ssize_t mem_write(struct file *filp, const char __user *buf, size_t size, loff_t *ppos)
  79. {
  80.   unsigned long p = *ppos;
  81.   unsigned int count = size;
  82.   int ret = 0;
  83.   struct mem_dev *dev = filp->private_data; /*获得设备结构体指针*/
  84.   
  85.   /*分析和获取有效的写长度*/
  86.   if (p >= MEMDEV_SIZE)
  87.     return 0;
  88.   if (count > MEMDEV_SIZE - p)
  89.     count = MEMDEV_SIZE - p;

  90.   /*从用户空间写入数据*/
  91.   if (copy_from_user(dev->data + p, buf, count))
  92.     ret = - EFAULT;
  93.   else
  94.   {
  95.     *ppos += count;
  96.     ret = count;
  97.     
  98.     printk(KERN_INFO "written %d bytes(s) from %d\n", count, p);
  99.   }
  100.   
  101.   have_data = true; /* 有新的数据可读 */
  102.     
  103.     /* 唤醒读进程 */
  104.     wake_up(&(dev->inq));

  105.   return ret;
  106. }

  107. /* seek文件定位函数 */
  108. static loff_t mem_llseek(struct file *filp, loff_t offset, int whence)
  109. {
  110.     loff_t newpos;

  111.     switch(whence) {
  112.       case 0: /* SEEK_SET */
  113.         newpos = offset;
  114.         break;

  115.       case 1: /* SEEK_CUR */
  116.         newpos = filp->f_pos + offset;
  117.         break;

  118.       case 2: /* SEEK_END */
  119.         newpos = MEMDEV_SIZE -1 + offset;
  120.         break;

  121.       default: /* can't happen */
  122.         return -EINVAL;
  123.     }
  124.     if ((newpos<0) || (newpos>MEMDEV_SIZE))
  125.         return -EINVAL;
  126.         
  127.     filp->f_pos = newpos;
  128.     return newpos;

  129. }

  130. unsigned int mem_poll(struct file *filp, poll_table *wait)
  131. {
  132.     struct mem_dev *dev = filp->private_data;
  133.     unsigned int mask = 0;
  134.     
  135.    /*将等待队列添加到poll_table */
  136.     poll_wait(filp, &dev->inq, wait);

  137.     
  138.     if (have_data) mask |= POLLIN | POLLRDNORM; /* readable */

  139.     return mask;
  140. }


  141. /*文件操作结构体*/
  142. static const struct file_operations mem_fops =
  143. {
  144.   .owner = THIS_MODULE,
  145.   .llseek = mem_llseek,
  146.   .read = mem_read,
  147.   .write = mem_write,
  148.   .open = mem_open,
  149.   .release = mem_release,
  150.   .poll = mem_poll,
  151. };

  152. /*设备驱动模块加载函数*/
  153. static int memdev_init(void)
  154. {
  155.   int result;
  156.   int i;

  157.   dev_t devno = MKDEV(mem_major, 0);

  158.   /* 静态申请设备号*/
  159.   if (mem_major)
  160.     result = register_chrdev_region(devno, 2, "memdev");
  161.   else /* 动态分配设备号 */
  162.   {
  163.     result = alloc_chrdev_region(&devno, 0, 2, "memdev");
  164.     mem_major = MAJOR(devno);
  165.   }
  166.   
  167.   if (result < 0)
  168.     return result;

  169.   /*初始化cdev结构*/
  170.   cdev_init(&cdev, &mem_fops);
  171.   cdev.owner = THIS_MODULE;
  172.   cdev.ops = &mem_fops;
  173.   
  174.   /* 注册字符设备 */
  175.   cdev_add(&cdev, MKDEV(mem_major, 0), MEMDEV_NR_DEVS);
  176.    
  177.   /* 为设备描述结构分配内存*/
  178.   mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev), GFP_KERNEL);
  179.   if (!mem_devp) /*申请失败*/
  180.   {
  181.     result = - ENOMEM;
  182.     goto fail_malloc;
  183.   }
  184.   memset(mem_devp, 0, sizeof(struct mem_dev));
  185.   
  186.   /*为设备分配内存*/
  187.   for (i=0; i < MEMDEV_NR_DEVS; i++)
  188.   {
  189.         mem_devp[i].size = MEMDEV_SIZE;
  190.         mem_devp[i].data = kmalloc(MEMDEV_SIZE, GFP_KERNEL);
  191.         memset(mem_devp[i].data, 0, MEMDEV_SIZE);
  192.   
  193.       /*初始化等待队列*/
  194.      init_waitqueue_head(&(mem_devp[i].inq));
  195.      //init_waitqueue_head(&(mem_devp[i].outq));

  196.   }
  197.    
  198.   return 0;

  199.   fail_malloc:
  200.   unregister_chrdev_region(devno, 1);
  201.   
  202.   return result;
  203. }

  204. /*模块卸载函数*/
  205. static void memdev_exit(void)
  206. {
  207.   cdev_del(&cdev); /*注销设备*/
  208.   kfree(mem_devp); /*释放设备结构体内存*/
  209.   unregister_chrdev_region(MKDEV(mem_major, 0), 2); /*释放设备号*/
  210. }

  211. MODULE_AUTHOR("David Xie");
  212. MODULE_LICENSE("GPL");

  213. module_init(memdev_init);
  214. module_exit(memdev_exit);
  1. #include <stdio.h>

  2. int main()
  3. {
  4.     FILE *fp = NULL;
  5.     char Buf[128];
  6.         
  7.     /*打开设备文件*/
  8.     fp = fopen("/dev/memdev0","r+");
  9.     if (fp == NULL)
  10.     {
  11.         printf("Open Dev memdev Error!\n");
  12.         return -1;
  13.     }
  14.     
  15.     /*写入设备*/
  16.     strcpy(Buf,"memdev is char dev!");
  17.     printf("Write BUF: %s\n",Buf);
  18.     fwrite(Buf, sizeof(Buf), 1, fp);
  19.     
  20.     sleep(5);
  21.     fclose(fp);
  22.     
  23.     return 0;    

  24. }
  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <unistd.h>
  4. #include <sys/ioctl.h>
  5. #include <sys/types.h>
  6. #include <sys/stat.h>
  7. #include <fcntl.h>
  8. #include <sys/select.h>
  9. #include <sys/time.h>
  10. #include <errno.h>

  11. int main()
  12. {
  13.     int fd;
  14.     fd_set rds;
  15.     int ret;
  16.     char Buf[128];
  17.     
  18.     /*初始化Buf*/
  19.     strcpy(Buf,"memdev is char dev!");
  20.     printf("BUF: %s\n",Buf);
  21.     
  22.     /*打开设备文件*/
  23.     fd = open("/dev/memdev0",O_RDWR);
  24.     
  25.     FD_ZERO(&rds);
  26.     FD_SET(fd, &rds);

  27.     /*清除Buf*/
  28.     strcpy(Buf,"Buf is NULL!");
  29.     printf("Read BUF1: %s\n",Buf);

  30.     ret = select(fd + 1, &rds, NULL, NULL, NULL);
  31.     if (ret < 0)
  32.     {
  33.      printf("select error!\n");
  34.      exit(1);
  35.     }
  36.     if (FD_ISSET(fd, &rds))
  37.      read(fd, Buf, sizeof(Buf));            
  38.     
  39.     /*检测结果*/
  40.     printf("Read BUF2: %s\n",Buf);
  41.     
  42.     close(fd);
  43.     
  44.     return 0;    
  45. }
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