[maemo-developers] N900 usb host + power charge

[From: Laurent GUERBY]

On Sat, 2009-09-19 at 15:44 +0300, Matan Ziv-Av wrote:
> On Sat, 19 Sep 2009, Laurent GUERBY wrote:
> 
> > On Fri, 2009-09-18 at 22:55 +0200, Kees Jongenburger wrote:
> >> Hi,
> >>
> >> I plan to create a proposal for the push n900[1] and I plan to use the
> >> usb port. I have the following question.
> >> When the device is in usb-host mode it should of course provide power does it?
> >> Is it possible to charge the device while it's in usb-host mode?
> >
> > The other way around: is it technically possible to have the n900 (and
> > n810) behave as an USB keyboard when connected to a PC? And even better
> > emulate any other USB device like a webcam, etc...?
> 
> I expect the hardware can do it, but it needs some work in kernel space. 
> The 2.6.29 kernel can appear as an ethernet, serial, mass storage, midi 
> audio or printer device. Anything else, needs a driver written.
> Gadget drivers can also be in user space, using gadgetfs, but I don't 
> know of any examples.

Hi,

Thanks for your answer! 

Looking around for "gadget" I found:

http://www.linux-usb.org/gadget/
<<
Other controller and gadget drivers are in development, but are
unreleased or not published here. Examples that have seen some degree of
light include:

      * HID driver (userspace, with gadgetfs),
      * "MTP" (Media Transfer Protocol, PTP++) driver (userspace, with
        gadgetfs),
      * two different printer class drivers (used in various products),
      * audio class driver (very experimental).
      * video class driver (very experimental).
>>

(HID is keyboard+mouse+other input devices)

I found a discussion of some issue with "Issues with
simulating a keyboard device with gadgetfs" here:

http://kerneltrap.org/mailarchive/linux-usb/2009/4/10/5455984/thread

Which points to an unapplied kernel patch.

So transforming a N900/N810 as a pocket USB keyboard (+ mouse/tablet),
and may be hacker wireless IP KVM using camera/webcam over LCD looks
like quite a bit of kernel-level work :).

Sincerely,

Laurent