1: /* slightly modified, for 32-bit platform */

   2:  

   3: #define MAX_INDEX                   0x8

   4: #define IOCTL_GET_FOO_STRUCT        0x20081018

   5:  

   6: struct foo_s {

   7:     int bla;

   8:     int blabla;

   9:     /* .... */

  10: };

  11:  

  12: struct foo_s foo_structs[MAX_INDEX];

  13:  

  14: /*

  15:  * 获取内核指定数组中索引为index的元素，用户层传入的缓冲区结构如下：

  16:  * 

  17:  * ,--------------------,

  18:  * |     u32 index      |  sizeof(u32), 0-based

  19:  * |--------------------|

  20:  * |    struct foo_s    |

  21:  * |        ...         |

  22:  * `--------------------`

  23:  *

  24:  */

  25:  

  26: static int foo_ioctl(struct inode *inode, struct file *file,

  27:         unsigned int cmd, unsigned long arg)

  28: {

  29:     /* .... */

  30:  

  31:     switch (cmd) {

  32:         /* .... */

  33:  

  34:         case IOCTL_GET_FOO_STRUCT:

  35:             {

  36:                 unsigned long not = 0;

  37:                 u32 *ip = (u32 *)arg;

  38:  

  39:                 printk(KERN_INFO "get index %d\n", *ip);

  40:                 if (*ip >= MAX_INDEX) {

  41:                     return -EINVAL;

  42:                 }

  43:                 check_foo_present(*ip); /* check if the struct valid */

  44:                 *ip = IOCTL_GET_FOO_STRUCT; /* take it as magic */

  45:                 not = copy_to_user((void *)(arg + sizeof(u32)), /* offset! */

  46:                         &foo_structs[*ip], sizeof(struct foo_s));

  47:  

  48:                 break;

  49:             }

  50:  

  51:             /* .... */

  52:  

  53:     } /* switch */

  54:  

  55:     return 0;

  56: }

  57: