FreeCalypso > hg > freecalypso-sw
diff rvinterf/README @ 173:f42854da4563
rvinterf: beginning of refactoring
author | Michael Spacefalcon <msokolov@ivan.Harhan.ORG> |
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date | Fri, 22 Nov 2013 05:56:07 +0000 |
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children | f114f5c547ec |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rvinterf/README Fri Nov 22 05:56:07 2013 +0000 @@ -0,0 +1,89 @@ +I (Spacefalcon the Outlaw, FreeCalypso developer) am still learning what kinds +of traffic may be passed across TI's RVTMUX binary-packet serial interface. We +already know that much of this traffic is debug trace output, i.e., +unidirectional and essentially unconditional output from the GSM device. All +of the "standard" firmwares we have (mokoN, our leo2moko which functions almost +identically, and Pirelli's fw) produce massive volumes of such trace output in +normal operation. We already know that this "unsolicited" trace output comes +in at least 3 different flavors: + +* RiViera traces emitted by rvf_send_trace() +* L1 traces +* G23 traces + +The RVTMUX interface can be used for more than just trace output, though: any +component in TI's fw suite can send and/or register to receive binary packets. +As I slowly work my way through various components which comprise TI's Leonardo +fw whose semi-source we use as our reference version, learning what they do and +reintegrating them in our own gsm-fw, I will undoubtedly uncover additional uses +to which the RVTMUX interface is put. + +Aside from the trivial provision in the RVT module itself whereby an external +host can send a command to the target to set a filter masking some of the RV +trace output, so far the only entity I've come across which accepts packets from +an external host is ETM (Enhanced Test Mode). ETM implements a registration +system of its own, whereby other modules can register with ETM to receive +certain external command messages passing first through RVT, then through ETM. + +Because I do not yet have a clear mental picture of *every* function for which +the RVTMUX interface will ever be used, it is correspondingly impractical to +decide on a once-and-for-all design of what the host-side software for talking +to this interface should be like. Therefore, it is currently premature to +expect any stability in the present rvinterf subdirectory of freecalypso-sw; I +may implement something one day, then toss it away the next day (without +providing much in the way of backward compatibility) when I come up with some +other idea. + +The current roadmap for what the rvinterf suite of host tools is envisioned to +look like eventually is as follows: + +rvtdump Opens the serial port, decodes TI's binary packet protocol, and + simply dumps every received/decoded packet on stdout in a human- + readable form. No provision for sending anything to the target. + Intended use: observing the debug trace output which all TI + firmwares emit as standard "background noise". This utility has + already been written, and it allows one to observe/log/study the + "noise" that appears on Pirelli's USB-serial port (running + Pirelli's original fw), as well as that emitted on the IrDA + (headset jack) port on the GTA02 by mokoN/leo2moko firmwares. + +rvinterf My plan is to make a copy of rvtdump, called rvinterf, and have + it act very much like rvtdump: receive TI's packets from the + serial port, decode them and print the decoded form on stdout. + However, rvinterf will also create a listening UNIX domain + socket to which other programs in the present suite will + connect. These other programs connecting through rvinterf will + be able to send packets to the target, as well as register to + receive certain kinds of target->host message packets. + +fc-tmsh FreeCalypso Test Mode Shell is my vision for the utility which + will provide a practically usable interface to ETM. ETM's + general mode of operation seems to be (weasel phrase inserted + because many other fw components may connect through ETM, and I + have yet to study all of them) command-response: an external + host sends a command to ETM, that command gets dispatched to the + proper registered handler, the command function is executed, a + response packet is composed, and finally that response is sent + back to the host. But because all code on the target side is + under active development and debugging, we should not expect + perfect lock-step behaviour on the interface; instead, our + fc-tmsh should be fundamentally asynchronous: when the user + enters a command, the appropriate command packet is sent to the + target, but we are prepared for target->host messages at any + time, without enforcing strict correspondence to issued + commands: let the developer-operator sort that out instead. + +The usage scenario I envision is that one will need to run rvinterf first +(either directly or through fc-xram) in one terminal window, leave it running, +then run fc-tmsh in another terminal window, and have it connect to rvinterf +via the local UNIX domain socket interface. Why such complexity, why not have +one program do everything? I suspect that in many debug/experimentation +sessions it will be necessary to use fc-tmsh on "noisy" targets, i.e., in +scenarios where the target is continuously spewing its "normal" voluminous debug +trace output, such that the "interesting" output as in responses to commands +gets drowned in the noise. In such a scenario it would be helpful to have one +terminal window in which one sees the transcript of the fc-tmsh session, +consisting of issued commands and received ETM responses without the general +noise, and another window in which one sees all RVTMUX interface activity in +real time - the latter would allow one to observe commands having side effects +outside of ETM, such as crashing the whole fw. :-)