Project Iris: Affordable, Instant Connectivity for Syborg/QEMU

Apologies for not updating here as often as I wanted – although in order to keep things concise, I won’t detail the reasons for my hiatus in this post.

That aside, whilst I can remember the details, I’d like to share a proposal for a novel (in my humble opinion – but I’m prepared to be corrected) method of potentially using unmodified, off-the-shelf Nokia handsets as a modem under Symbian OS running on QEMU.

Please note that I have so far been unable to implement this, or test certain individual components (e.g. the Linux PhoNet stack); although I believe from the research that I’ve done that individual components should work in isolation.

Additionally, this isn’t intended to be a competitor to the excellent Wild Ducks project, or the ad-hoc efforts surrounding getting regular modems utilising Hayes/AT commands to work, either. (It’s for folks who for whatever reason either can’t afford to acquire a fully fledged Wild Ducks set-up, don’t want to commit themselves for the long-term, or just want a quick-‘n’-dirty way to test stuff that requires network connectivity).

With that in mind, I’ll introduce the architecture diagram, and hopefully try to provide further details – because a picture is apparently worth a thousand words:

Click to view full size

The system itself consists of the following components, in no specific order:

  • A version of QEMU with customisations specific to the Symbian Platform, as detailed in my ancient post on the Symbian Blog – and a few others, since then!
  • Two brand new components, which will be described in further detail later (the TI SSI bus “pseudo-modem” and the raw PhoNet-to-SSI bridge)
  • The Linux PhoNet protocol stack, which was contributed to the mainline Linux kernel by Nokia on behalf of members of what was once known as the “Maemo Computers” department (if memory serves correct)
  • Your favourite Nokia device, providing that it supports USB connectivity and the “PC Suite” profile – since that’s how we can access certain baseband services via PhoNet! (A well-kept secret, so it seems)…
  • The Symbian Platform (which consists of the Symbian OS, UI framework, middleware and other components) and the baseport – Syborg, in the case of Project Iris
  • Nokia’s baseband “TSY” (telephony support plug-in), which should work in conjunction with a well-designed TI SSI bus “pseudo-modem” and the raw PhoNet-to-SSI bridge to simulate the presence of a real Nokia baseband by proxy 🙂

The most interesting components are the TI SSI bus “pseudo-modem” and the raw PhoNet-to-SSI bridge, which are pivotal to making this thing work.

The raw PhoNet-to-SSI bridge can potentially either be integrated into QEMU, or left standalone –  although designing the IPC mechanism for the latter use-case is left as an exercise for the reader.

Communication with the device could occur via either a /dev/phonet0 device node (if such a thing existed, but according to this IRC log, it seems that it doesn’t under certain circumstances), or directly bound low-level datagram/pipe sockets to communicate with the user’s handset via raw PhoNet/ISI packets encapsulated in USB frames.

Obviously, the raw PhoNet-to-SSI bridge will encapsulate and decapsulate PhoNet packets that are transmitted/received by the handset into Texas Instruments-proprietary SSI frames for consumption by the “pseudo-modem”.

The “pseudo-modem” works in conjunction with the Nokia TSY (as mentioned earlier) and the raw PhoNet-to-SSI bridge; and will be a brand new, integral component of QEMU. It has minimal state of its own; and other than creating the illusion of a genuine Nokia/TI modem’s presence, it serves solely to transport packets between the bridge and the TSY.

Finally, the interaction between the TSY, network and telephony stacks and other parts of Symbian OS are extensively documented elsewhere.

For those curious about the title, the “instant” bit refers to the fact that as of recent versions of the Linux kernel and NetLink stuff, things should Just Workâ„¢ when a PhoNet device is connected (according to this page and this presentation from 2009), and that limited hardware knowledge is necessary to use one – just plug it in and switch it on.

The “affordable” bit refers to the fact that Nokia devices are relatively low-cost, easy to obtain, and plentiful (unlike specialist hardware such as the BeagleBoard and standalone GSM modems – as great as they are, for example).

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