（1）我用的mx6ul，内核是3.14.38。将编译生成的g_serial.ko文件，执行 insmod g_serial.ko 命令，报错如下：
root@freescale /$ insmod g_serial.ko
g_serial: Unknown symbol usb_remove_function (err 0)
g_serial: Unknown symbol usb_get_function_instance (err 0)
g_serial: Unknown symbol usb_add_config_only (err 0)
g_serial: Unknown symbol usb_string_ids_tab (err 0)
g_serial: Unknown symbol usb_get_function (err 0)
g_serial: Unknown symbol usb_composite_unregister (err 0)
g_serial: Unknown symbol usb_put_function (err 0)
g_serial: Unknown symbol usb_add_function (err 0)
g_serial: Unknown symbol usb_composite_probe (err 0)
g_serial: Unknown symbol usb_composite_overwrite_options (err 0)
g_serial: Unknown symbol usb_otg_descriptor_alloc (err 0)
g_serial: Unknown symbol usb_put_function_instance (err 0)
g_serial: Unknown symbol usb_otg_descriptor_init (err 0)
g_serial: Unknown symbol usb_ep_autoconfig_reset (err 0)
insmod: can't insert 'g_serial.ko': unknown symbol in module, or unknown parameter
（2）我在内核的根目录下执行make命令，可以生成xxx.ko文件，但是执行make zImage -j4命令编译生成不了xxx.ko文件，不能将驱动文件打包
