Based on my initial debugging, USB CV TD 9.13 will consecutively set device to configuration #1 by sending "Set Configuration" transfer. So, in set_config() function, it will try to disable each interface first and then set up each interface. That is, the fsg_disable() will be called first and then fsg_set_alt(). There might be a chance that the request (FSG_STATE_DISCONNECT) from fsg_disabled() has not been handled by fsg_main_thread before fsg_set_alt() is called. In this case, fsg_set_alt() will try to queue its request (FSG_STATE_CONFIG_CHANGE) to fsg_main_thread, but find that FSG_STATE_DISCONNECT has not been handled. Because the priority of FSG_STATE_DISCONNECT is higher than FSG_STATE_CONFIG_CHANGE, FSG_STATE_CONFIG_CHANGE will be discarded accordingly. This might lead to the missing of usb_composite_setup_continue() which result in the failure of "Set Configuration" transfer.
Will push a new patch to fix this issue. --nvpublic
