My system is Lite5200 with DENX Embedded Linux running on it.I want to connect USB mass storage devices to my computer's USB port.But I found there is no driver in kernel.(when I use 'make xconfig' the USB mass storage devices driver is in grey).How can I download/install the driver and active my USB disk?

Like I already told you in a private e-mail, you provide too little information to be useful.

1. Your questions has little to do with U-Boot; please look for an appropriate mailing list (i.e. don't bother Wolfgang in his continuous problem solving/debugging frenzy).

2. Furthermore, your remark does not make sense, IIRC all kernels since 2.2.x have some kind of USB support

3. If you have these kinds of problems, you need to provide version numbers (kernel, development environment).

4. I would assume you are missing some dependent functionality, that's why the option is disabled (never used xconfig though).

5. First, try to compile and configure a kernel for your desktop system before jumping onto your development environment... If you get USB working on your desktop system, the configuration will be similar for your embedded solution.