To config JTX1 USB 3.0 port as device mode:
1> Modify the kernel following attached patch.
2> Enable Android Gadget:
echo 0 > /sys/class/android_usb/android0/enable
echo 0955 > /sys/class/android_usb/android0/idVendor
echo 7E00 > /sys/class/android_usb/android0/idProduct
echo mass_storage > /sys/class/android_usb/android0/functions
echo 0 > /sys/class/android_usb/android0/bDeviceClass
dd if=/dev/zero of=/home/ubuntu/msc.ext4.img bs=1M count=1k
mkfs.ext4 /home/ubuntu/msc.ext4.img
echo /home/ubuntu/msc.ext4.img > /sys/class/android_usb/android0/f_mass_storage/lun/file
echo 1 > /sys/class/android_usb/android0/enable
3> Plug in USB3.0 cable(Swap the TX/RX signal for normal USB3.0 A to A extension cable)
4> Plug in USB2.0 cable(The system need VBUS detect to identify a USB3.0 host connected)
The host will detect a storage device which emulated from JTX1