ubuntu 9.10下认不到usb转串口设备？

Add one function to the user.c file using the following header:
int add(int par1,int par2);
This function must perform (in the assembler) the same as:
return par1+par2;
The entire code of the function will be written in assembler language. This
means that you must review the way a value is returned in assembler; (in
which register will the result have to be placed?). You cannot use the
input/output parameters of inline assembler.

由于是英语，也不是很明白，可能是在zeos项目中的user.c文件下用汇编写这个功能，有知道的高手帮忙下吗？谢谢了