Originally Posted by kindle-hopes
Update: the problem seems to be that the g_file_storage module gets loaded, but somehow does not get the info which directory to export to the USB gadget. Thus the computer sees a storage device, but no actual partition.
looks like the following command
echo /dev/mmcblk0p4 > /sys/devices/platform/arc_udc/gadget/gadget-lun0/file
solves the problem. It also looks like that it should be issued only once after the arc_udc gets loaded.