After a bit of hacking around I was able to enable usb otg on my N1!
I've had a look at kernel sources for device with similar SoC (Nexus Player) and saw an interesting debugfs entry. To my surprise it worked like a charm and immediately detected the attached usb hub with a thumb drive, it even powered the hub so I didn't have to use an external power source!
To enable host mode, the following command has to be enterted in root console:
echo A > /sys/kernel/debug/usb/dwc3_debugfs_root/otg_id
Caveats (will try to find a way to resolve them):
- after enabling host mode N1, won't charge from the usb port - a reboot is required to enable the charging again
- probably same is true for pheripherial mode (connecting n1 to a pc). In theory, changing a to b in the above echo command should bring the tablet back to normal mode but for some reason it won't charge without a reboot so I'm assuming that same is true for non otg usb connectivity. Will have a look at the sources and debug messages to find out what's going on