c - 从 ruby​​ 访问系统资源

Question

我正在为 Raspberry Pi 的 Hitachi-44780 库编写一个 ruby​​ 包装器。库本身是用 C 编写的。我有以下代码试图打开/dev/mem

void setup_io()
{

   /* open /dev/mem */
   if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
      printf("can't open /dev/mem \n");
      exit (-1);
   }
   // Allocate MAP block
   if ((gpio_mem = malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
      printf("allocation error \n");
      exit (-1);
   }
   // Make sure pointer is on 4K boundary
   if ((unsigned long)gpio_mem % PAGE_SIZE)
     gpio_mem += PAGE_SIZE - ((unsigned long)gpio_mem % PAGE_SIZE);
   // Now map it
   gpio_map = (unsigned char *)mmap(
      (caddr_t)gpio_mem,
      BLOCK_SIZE,
      PROT_READ|PROT_WRITE,
      MAP_SHARED|MAP_FIXED,
      mem_fd,
      GPIO_BASE
   );
   if ((long)gpio_map < 0) {
      printf("mmap error %d\n", (int)gpio_map);
      exit (-1);
   }
   gpio = (volatile unsigned *)gpio_map;
}

问题是我如何在不成为超级用户的情况下使用 gem？现在打开内存时它会失败。