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−FreeCalypso Magnetite firmware project
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−======================================
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−
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−As of A.D. 2018, FC Magnetite is the primary official Calypso firmware source
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−tree for the FreeCalypso family of projects.  This maintained and evolving
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−source can be built in many different configurations for several different
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−hardware targets, and is currently used in the following ways:
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−
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−* The official production firmwares for our fully supported GSM+GPRS modem
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−  products (FCDEV3B and the modem part of Openmoko devices) are built from
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−  this source tree.  See doc/Modem-configs for this mode of usage.
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−
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−* The work in progress toward a future complete FreeCalypso phone handset
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−  (also known as a Libre Dumbphone) is being done in this source tree.
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−  See doc/Handset-goal for more info about this project direction.
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−
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−* One can play with FreeCalypso and get a taste for it using certain hardware
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−  that used to be readily available and which most people in the phone hacking
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−  scene already have: Motorola C1xx and Pirelli DP-L10.  Firmware images of the
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−  "hacking toy" sort can be built for these devices from the present source
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−  tree, and one can exercise most of the functions and capabilities of
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−  FreeCalypso (with the notable exception of CSD and GPRS) on this historical
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−  but available-to-most-people hardware.  See doc/C1xx-Howto, doc/Pirelli-Howto
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−  and doc/Voice-pseudo-modem for more information.
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−
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−Functionality
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−=============
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−
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−TI's GSM mobile station firmware architecture supports two ways in which the
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−GSM device may be controlled: via AT commands from an external host and/or via
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−a local UI on devices with LCD & keypad hardware.  (I said "and/or" because the
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−two mechanisms can coexist.)  The code we got from TI (TCS211) is very solid
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−and mature in the modem configuration (control via AT commands only, no UI, no
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−battery management, no traditional handset on/off control), but the additional
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−code layers that are needed for handset products but not for modems came in a
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−very rough "proof of concept" condition, nowhere close to a usable product.
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−
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−In FC Magnetite we further maintain and support the solid code base we got for
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−the modem functionality, and we are also working to improve the support for
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−handset products and bring it into a practically usable state.  We have already
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−implemented an entirely new battery charging and discharge monitoring driver
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−that actually works on our target hw (of the two we got from TI, one was
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−bitrotten and the other was designed for charging hardware that is quite
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−different from what we are working with), and we shall hopefully start working
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−on the UI soon - see doc/Handset-goal for more info.
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−
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−Both TI's original modem fw (TCS211) and our recreation thereof in this
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−Magnetite project support not only voice calls and SMS, but also CSD, fax and
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−GPRS.  This advanced functionality is fully supported on our own GSM MS
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−development board (FCDEV3B), where both Calypso UARTs are presented directly to
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−the developer, as well as on the embedded Calypso modem in Openmoko GTA01/02
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−smartphones, where the AT command channel with CSD, fax and GPRS capabilities
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−is connected to the phone's application processor.
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−
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−Build system
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−============
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−
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−Even though FC Magnetite is essentially unchanged TCS211 code base and builds
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−using TI's proprietary TMS470 compiler under Wine, the build system is entirely
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−new.  TI's TCS211 build system, called BuSyB, works by way of a Java tool
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−generating a customized makefile for each desired build configuration, based on
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−lots of magic contained in a big repository of XML files.  There are a bunch of
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−Perl scripts involved as well.  The Java tool that does the heavy lifting exists
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−only as compiled Java bytecode sans source, and the surrounding Perl scripts
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−aren't very understandable either.  And the whole thing thoroughly assumes a
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−Windows environment (drive letters, backslashes, case-insensitive file system)
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−throughout.  As a result, when working with TCS211 fw with its original build
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−system, we had to treat these BuSyB-generated makefiles almost as being blobs in
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−themselves: regenerating a makefile from XML magic required major effort, there
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−were some bugs in the makefile generation which we couldn't fix and thus we had
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−to edit the makefiles manually after each regeneration - it was an utter mess,
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−and absolutely not an acceptable way to build a forward-looking, community-
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−serving project.
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−
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−In FC Magnetite I have recreated the relevant parts of the TCS211 build system,
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−using Bourne shell magic instead of Java and XML.  Just like TI's BuSyB, ours
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−is a makefile generation system: in order to compile the firmware in a
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−particular desired configuration, you run a shell script to select the config
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−you would like.  This shell script will create a dedicated build directory tree
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−to fully contain this build, and populate it with generated Makefiles and some
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−other bits - then you go into the just-created build directory and run make
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−there.  The source and build trees are thus cleanly separated.  See
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−doc/Compiling for detailed instructions.
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−
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−Another key difference from our previous TCS211-based firmware offerings is that
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−even though we still have to run TI's compiler binaries under Wine, the Wine
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−invokation has been moved from the top (root) of the build process to the
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−bottom leaves.  With our previous TCS211-based works you would run Wine at the
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−top, and then the entire build process would proceed in the Windows environment,
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−using Windows versions of make and other nonsense.  Not so in FC Magnetite:
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−in this firmware project all shell scripts, Makefiles, Perl scripts and other
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−build system accessories run at the native Unix level, and Wine is only invoked
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−at the lowest level by individual tool wrappers: for example, TI's compiler
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−binary cl470.exe is encapsulated in a Unix shell script called cl470 that
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−invokes Wine to run the Windows binary, presenting the illusion of a native
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−Unix tool to all upper levels.
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−
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−As yet another defenestration measure, all source files are checked into this
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−tree with Unix line endings.
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−
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−Two versions of the G23M protocol stack
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−=======================================
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−
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−A major component of all functional firmware configurations is the mass of code
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−that implements layers 2 and 3 of the GSM+GPRS protocol stack, called G23M.  In
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−FC Magnetite we have the option of using one of two different versions of this
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−key firmware component:
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−
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−* The original G23M version from Openmoko: this version is believed to be very
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−  stable because it has been used (successfully to the best of our knowledge)
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−  by Openmoko, and it came from TI's TCS211 program that officially targeted
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−  the Calypso chipset - but it exists only as binary object libraries with no
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−  corresponding source.  The lack of source means no ability to change the
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−  feature configuration (what is enabled and what is disabled), very difficult
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−  to debug if something does go wrong - all of the usual problems of software
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−  without source.
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−
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−* A newer version from TI's TCS3/LoCosto program.  This version came to us in
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−  the form of full C source, and because this fw component is chipset-
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−  independent (unlike L1), we have successfully produced a TCS2/TCS3 hybrid in
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−  which the new G23M code from TCS3.2 is grafted onto the chipsetsw foundation
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−  from TCS211, which we have reconstructed into full C source form as well.
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−
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−Each of the two G23M PS versions also has its own version of the Application
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−Control Interface (ACI) layer to go with it, which we call aci2 and aci3 -
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−except that in the case of ACI, we have the full source for both versions.
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−
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−The new TCS2/TCS3 hybrid config is the way forward, as our goal is to have no
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−blobs in our firmware - having the full source is a prerequisite for maintaining
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−a software product.  FC Magnetite supports building both configurations in order
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−to facilitate the transition, and as of this writing, we still need to add a few
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−bits to the new version of ACI in order to achieve 100% feature parity with
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−Openmoko.
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−
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−Other blobs
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−===========
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−
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−The TCS2/TCS3 hybrid firmware is built almost entirely from source; the only
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−components which are linked in the form of prebuilt libraries are GPF, Nucleus
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−and the TMS470 compiler's equivalent of libc/libgcc.  It needs to be noted that
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−these components are so stable and configuration-independent that they were
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−used mostly in prebuilt library form even inside TI.  In the case of GPF we've
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−got the corresponding source for most of the modules within those libs; for the
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−few modules for which the original source has been lost, we've already done a
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−rough first-draft reconstruction as part of our previous gcc-built GSM fw
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−efforts, and we only need to polish this reconstruction in order to have
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−deblobbed GPF in our mainline production fw.  In the case of Nucleus we likewise
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−have another version of it in full source form which has been proven good in
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−other FreeCalypso firmware projects.
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−
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−The planned successor to FC Magnetite (tentative planned name Selenite) will
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−use the hybrid config for the G23M PS, deblobbed GPF and the source-enabled
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−version of Nucleus, resulting in blob-free firmware except for the proprietary
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−TMS470 compiler and its equivalent of libc/libgcc.  Transition to building with
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−gcc (like in FreeCalypso Citrine) will follow afterward, completely exiting the
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−land of blobs and proprietary build tools.
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−
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−Further reading
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−===============
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−
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−For various instructions and notes specific to this FreeCalypso Magnetite
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−firmware, look in the doc directory.  For more information about the overall
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−FreeCalypso project and our hardware building aspirations, go to our website:
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−
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−https://www.freecalypso.org/