开发遇到在嵌入式Linux下，同时开启RNDIS和Mass Storage两个功能，
可是用的版本为Linux 2.26.27，还不支持此功能，
去 http://git.kernel.org/查询，找到了支持此版本的记录：
USB: g_multi: Multifunction Composite Gadget added
The Multifunction Composite Gadget has two configurations
consisting of Ethernet (RNDIS in first and CDC Ethernet in
second configuration), CDC Serial and File-backed Storage
functions.
When connected to a Windows host, the first configuration
is chosen thus gadget provides RNDIS Ethernet, serial and
mass storage whereas when connected to Linux host, second
configuration is chosen thus providing CDC Ethernet,
serial and mass storage.
Which configurations are built can be configured via
KConfig options.
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f176a5d81214864904d285912da02c4bc0e9041a