undefined reference to `dm9000_initialize'

u-boot2009.08dm9000x.c里面的对应代码：

static int dm9000_initialize(bd_t *bis)

{
        struct eth_device *dev = &(dm9000_info.netdev);


        dev->init = dm9000_init;
        dev->halt = dm9000_halt;
        dev->send = dm9000_send;
        dev->recv = dm9000_rx;
        sprintf(dev->name, "dm9000");


        eth_register(dev);


        return 0;
}

网上教程：

添加板载DM9000网卡初始化代码，如下：

#gedit board/samsung/my2440/my2440.c

#include <net.h> #include <netdev.h> extern int dm9000_initialize(bd_t *bis); #ifdef CONFIG_DRIVER_DM9000 int board_eth_init(bd_t *bis) {     return dm9000_initialize(bis); } #endif

为什么还是提示我这个错误呢？？、在网上查了一下午了，试了各种方法都不行，求大神解答，谢谢
board/samsung/smdk2440/libsmdk2440.a(smdk2440.o): In function `board_eth_init':
/work/systemok/u-boot-2009.08/board/samsung/smdk2440/smdk2440.c:142: undefined reference to `dm9000_initialize'
make: *** [u-boot] 错误 1