N900 uses an integrated Mentor Graphics OTG controller * (musb
mhdrc ) but hardware is acording wiki nxp isp 1707 **.
When a hacked cable ( a mode) is plugged into usb port on vbus it can detect a voltage pulse coming from n900. This is part of usb otg signaling protocol. Also on /sys/devices/platform/musb_hdrc/mode we can read a_idle
until now we have :
1) ID pin state is transmited to kernel
2) voltage can be applied on vbus
so in my opinion the limitation is only at software level
why nokia coose NXP ( former Philips ) and Mentor Graphics usb kernel Nucleus instead of full TI asics line wich can be suported in desktop like linux I can't understand, meanwhile apple continue to sell crap ifone.
Why Nokia screw usb host mode also i can't understand. Battery charging when usb host mode is selected is possible and with aid an external device host mode can be achieved ( I will ad a link later )
I start digging on datasheets but without nokia support community can't do more.
BTW in otg mode host and peripheral mode can be swaped . Can n900 perform this shift ?

* http://www.mentor.com/products/embed...s/nucleus_usb/
** http://wiki.maemo.org/N900_Hardware_isp1707