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annotate doc/TIFFS-Overview @ 923:10b4bed10192

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gsm-fw/L1: fix for the DSP patch corruption bug The L1 code we got from the LoCosto fw contains a feature for DSP CPU load measurement. This feature is a LoCosto-ism, i.e., not applicable to earlier DBB chips (Calypso) with their respective earlier DSP ROMs. Most of the code dealing with that feature is conditionalized as #if (DSP >= 38), but one spot was missed, and the MCU code was writing into an API word dealing with this feature. In TCS211 this DSP API word happens to be used by the DSP code patch, hence that write was corrupting the patched DSP code.
author Mychaela Falconia <falcon@ivan.Harhan.ORG>
date Mon, 19 Oct 2015 17:13:56 +0000
parents 14618bd924ec
children
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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1 All TI GSM firmwares known to this author (FreeCalypso developer Space Falcon)
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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2 implement some kind of flash file system, or FFS. Several different FFS code
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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3 implementations, and correspondingly several different on-flash data formats,
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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4 have been used throughout the history of TI's involvement in the wireless
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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5 terminal business. The FFS incarnation of primary interest to the FreeCalypso
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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6 project is the one invented by Mads Meisner-Jensen at TI in the early 2000s
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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7 (at least according to the comments in the sources available to us), and it is
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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8 relevant to us in the following ways:
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9
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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10 * When targeting the GSM modem in Openmoko's GTA01/02 smartphones, we need to
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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11 work with the original FFS from the factory (call it MokoFFS), the same FFS
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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12 as used by the mokoN firmwares: this FFS contains the IMEI and the RF
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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13 calibration values from the factory, which we most certainly don't want to go
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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14 without.
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15
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16 * The Leonardo firmware semi-src which we are using as the reference for
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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17 building our own full source, multi-target GSM fw contains a turnkey-working
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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18 implementation of this very FFS, using the on-flash format in question and
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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19 providing run-time APIs expected by the rest of the GSM fw suite. Following
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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20 the principle of ``if it ain't broke, don't fix it'', we can use this FFS not
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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21 only on the gtamodem target, but also on other targets, including those where
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22 we would be starting from a blank state and thus have the freedom to use
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23 whatever FFS we like.
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24
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25 * The original proprietary fw on the Pirelli DP-L10 phone also happens to use
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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26 an FFS in the same format. Pirelli's FFS does *not* contain the IMEI or any
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27 of the RF calibration values though, and trying to reuse it directly for our
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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28 own FC GSM fw seems to be more trouble than benefit - so we'll probably have
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29 our fw start with a blank TIFFS instead - but there is still insight to be
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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30 gained from in-vitro examination of captured Pirelli FFS images.
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31
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32 Naming
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33 ======
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34
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35 I have previously referred to the FFS format in question as Mokopir-FFS or
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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36 MPFFS, from "Moko" and "Pirelli". I was originally hesitant to call it TIFFS,
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37 as lacking the source code, I had no way of knowing whether the FFS format and
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38 implementation were of TI's own invention, or something that TI licensed as a
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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39 black box from one of their many proprietary software partners. (I was unable
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40 to identify it as any well-known, industry-standard FFS format, but absence of
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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41 evidence is not evidence of absence.) But now that we have TI's original source
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42 code which implements this FFS (first the MV100-0.1.rar source, then the full
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43 Leonardo one), complete with comments and a HISTORY file, we know that our FFS
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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44 was invented and implemented by someone named Mads Meisner-Jensen at TI - I'm
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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45 guessing in the SSA group in Nice, France.
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46
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47 I am now making a naming transition from MPFFS to TIFFS: there is really no
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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48 link between this FFS format and the Openmoko+Pirelli duo, other than the
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49 happenstance of me having first encountered this FFS on these two GSM device
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50 brands, and the name TIFFS is more neutrally-descriptive.
227
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51
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52 What it is
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53 ==========
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54
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55 In a rare departure from TI's norm (most of TI's GSM firmware and associated
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56 development tools suffer from heavy Windows poisoning), what I call TIFFS is
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57 very Unixy. It is a file system with a hierarchical directory tree structure
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58 and with Unixy forward-slash-separated, case-sensitive pathnames; the semantics
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59 of "what is a file" and "what is a directory" are exactly the same as in UNIX;
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60 and TIFFS even supports symlinks, although that support is a little under-
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61 developed, and apparently no FFS symlinks were ever used in any production GSM
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62 device. Thus the FFS implemented in TI-based GSM devices (modems and
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63 "dumbphones") is really no different from, for example, JFFS2 in embedded Linux
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64 systems.
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65
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66 (The only traditional UNIX file system features which are missing in TIFFS are
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67 the creation/modification/access timestamps and the ownership/permission
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68 fields.)
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69
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70 The FFS in a GSM device typically stores two kinds of content:
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71
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72 * Factory data: IMEI, RF calibration values, device make/model/revision
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73 ID strings etc. These files are expected to be programmed on the factory
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74 production line and not changed afterward.
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75
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76 * Dynamic data written into the FFS in normal device operation: when you use a
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77 "dumbphone" running TI-based firmware, every time you store something "on the
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78 phone" or in "non-volatile memory", that item is actually stored in the FFS.
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79 (Where else, if you think of it?) That includes contacts and received SMS
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80 stored "on the phone" instead of the SIM, any selections you make in the
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81 settings/preferences menus which persist across reboots (power cycles), call
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82 history etc.
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83
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84 It needs to be noted that the "dynamic data" aspect of FFS usage applies not
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85 only to complete phones, but also to modems like the one used in the GTA01/02.
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86 One would naively think that non-volatile storage of data in flash outside of
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87 factory programming would be needed only in a device with its own UI, and that
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88 a modem subservient to external AT commands would be completely stateless
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89 across reboot/power cycles; but that is not the case in actuality. TI's GSM
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90 firmwares, including the Openmoko ones (the "standard" mokoN), are designed to
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91 always "mount" their FFS with read/write access; TI's FFS implementation in the
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92 firmware has no concept of a "read-only mount".
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93
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94 I am still investigating just what kinds of data are routinely written into the
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95 non-volatile FFS by the firmware in normal operation on devices like the GTA0x
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96 modem, but there most definitely are some.
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97
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98 There is no hard separation between "static" and "dynamic" data in the file
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99 system structure; TIFFS is thus akin to an embedded Linux system with just a
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100 single root file system containing both "static" files like userland binaries
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101 and "dynamic" ones like configuration files under /etc which the user is
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102 expected to edit with vi after logging into the box, or log and similar files
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103 created by the system itself under /var, for example.
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104
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105 Where it lives
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106 ==============
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107
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108 The type of flash memory used in Calypso GSM modems and "dumbphones" is called
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109 NOR flash. This NOR flash memory is physically divided (by the design of the
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110 flash chip itself) into units called "sectors" or more descriptively, erase
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111 blocks. The typical NOR flash sector size (in Calypso GSM devices) ranges from
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112 64 KiB in the GTA02 modem's NOR flash (4 MiB total) to 256 KiB in the
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113 S71PL129NC0 flash+RAM chip used in the Pirelli DP-L10 (16 MiB of flash total).
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114 The key physical property is that any bit may be changed from a '1' to a '0' at
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115 any time, in any combination, but resetting of '0' bits back to ones can be
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116 done only on the granularity of these largish sectors, in an operation called
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117 "sector erase".
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118
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119 The location of TIFFS within the flash memory of a given GSM device is defined
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120 by the firmware design of that device, but is always some integral number of
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121 contiguous flash sectors. Some examples:
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122
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123 * On the GTA01/02 GSM modem, FFS occupies 7 sectors of 64 KiB each, starting at
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124 flash offset 0x380000.
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125
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126 * On the Pirelli DP-L10, the FFS used by the original proprietary fw occupies
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127 18 sectors of 256 KiB each (for 4.5 MiB in total), starting at the beginning
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128 of the 2nd flash chip select (0x02000000 in the ARM7 address space).
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129
430
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130 * On Motorola/Compal C139/140 phones, the FFS used by the original proprietary
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diff changeset
131 fw occupies 5 sectors of 64 KiB each (320 KiB in total), starting at 0x370000.
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132 C11x/123 use smaller FFS configurations, whereas C155/156 seem to have
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133 switched to some other FFS format, different from our familiar TIFFS.
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134
227
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135 * The smallest real FFS configuration called for by the table in dev.c in TI's
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diff changeset
136 original Leonardo fw source is 3 sectors of 64 KiB each; the same table also
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137 sports a 4 KiB x 4 configuration for RAM-based testing (emulation of FFS in
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138 RAM without real flash).
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139
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140 * The largest FFS configuration that has been envisioned by the original
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diff changeset
141 designers seems to be somewhere around 128 sectors.
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diff changeset
142
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143 Each flash sector used for TIFFS begins with this 6-byte signature:
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144
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145 46 66 73 23 10 02
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146
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147 The first 4 bytes are 'Ffs#' in ASCII, and the following two bytes are the
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148 format version number of 0x0210 in little-endian byte order. The following two
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diff changeset
149 bytes give a count of how many times that sector has been erased and rewritten
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diff changeset
150 (FF FF in "fresh" or "virgin" FFS images), and the following byte indicates
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diff changeset
151 that block's role and status in the FFS life cycle.
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152
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153 How it works
1852900ce9ea doc/TIFFS write-up
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diff changeset
154 ============
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diff changeset
155
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156 Just like JFFS2 and other high-quality flash file systems, TIFFS is designed to
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157 recover gracefully from any possible power failure or crash: one can yank the
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diff changeset
158 battery from the GSM device (or induce a firmware crash) at the most mis-
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diff changeset
159 opportune moment in the middle of an FFS write operation, and the FFS is
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diff changeset
160 expected to recover on the next boot cycle. I won't be able to document here
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diff changeset
161 all gory details of exactly how this goal is achieved, partly because I haven't
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diff changeset
162 studied the code to the requisite level of depth myself yet, but all of the
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diff changeset
163 responsible code lives under gsm-fw/services/ffs in this freecalypso-sw source
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parents: 224
diff changeset
164 tree; feel free to study it.
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diff changeset
165
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diff changeset
166 In its "normal" or "clean" state (i.e., when not in the middle of a write
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diff changeset
167 operation or recovery from an ungracefully interrupted one), a TIFFS instance
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diff changeset
168 consists of the following 3 types of blocks:
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diff changeset
169
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diff changeset
170 * One block containing inode records, indicated by AB in its type/flags/status
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diff changeset
171 byte in the block header;
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172 * N-2 blocks (where N is the total number of flash sectors allocated for the
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diff changeset
173 FFS) containing (or waiting to be filled with) data chunks - indicated by BD
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174 in the type/flags/status byte;
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175 * One "free" block, indicated by BF - destined to become a new AB or a new BD
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diff changeset
176 at some point.
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diff changeset
177
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diff changeset
178 Each object written into the FFS (file, directory or symlink) consists of a
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diff changeset
179 16-byte inode record written into the AB block and a data chunk written into
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diff changeset
180 one of the BD blocks. The data chunk includes the name of the object, hence
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diff changeset
181 one is required even for directories. Data chunks are contiguous, uncompressed,
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diff changeset
182 and subject to an upper size limit of 2048 or 8192 bytes, depending on the FFS
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parents: 224
diff changeset
183 configuration. Files larger than this limit are stored in a "segmented" form,
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diff changeset
184 giving rise to a 4th inode or object type (after file, directory and symlink):
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diff changeset
185 segment. Each segment of a segmented file consists of not only a data chunk,
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diff changeset
186 but also an inode record for the segment, which gives the location of the data
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diff changeset
187 chunk and ties the segment object into the overall FFS structure, making it
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diff changeset
188 accessible.
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diff changeset
189
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diff changeset
190 Because aside from complete sector erasure, flash memory bits can only
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diff changeset
191 transition from '1' to '0' but not the other way around, overwriting an existing
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parents: 224
diff changeset
192 file with some new content (an operation which any reasonable file system must
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diff changeset
193 implement in some way) cannot be done in place. Instead like most flash file
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diff changeset
194 systems, TIFFS implements this common operation by writing the new version of
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diff changeset
195 the file to a new location (previously blank flash) and then invalidating the
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diff changeset
196 old version - and doing all that while keeping in mind the possibility of an
1852900ce9ea doc/TIFFS write-up
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diff changeset
197 ungraceful crash or powerdown at any moment, and the requirement of recovering
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diff changeset
198 gracefully from any such event.
1852900ce9ea doc/TIFFS write-up
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diff changeset
199
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diff changeset
200 Of course as an FFS receives more write activity, even if one keeps overwriting
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diff changeset
201 some existing files with new content of the same size, without adding to the
1852900ce9ea doc/TIFFS write-up
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diff changeset
202 visible total content size (think du(1) command), eventually all remaining blank
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parents: 224
diff changeset
203 flash space will fill up. At that point (or at some earlier point, depending
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parents: 224
diff changeset
204 on the FFS design and/or configuration) the FFS has to invoke a compaction or
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parents: 224
diff changeset
205 reclamation or garbage collection procedure: any "mixed" blocks containing both
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
206 valid and stale data are transitioned into a "stale-only" state by having the
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
207 active data moved to a new block, and then the "all stale" blocks are subjected
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parents: 224
diff changeset
208 to sector erasure, becoming new blank sectors. The logic responsible for these
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
209 operations once again needs to be resilient to the possibility of a crash or
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
210 powerdown occurring at the most mis-opportune moment, and it also needs to
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diff changeset
211 implement flash wear leveling: there is a physical limit to how many times a
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parents: 224
diff changeset
212 given flash sector can be erased and rewritten before it goes bad.
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diff changeset
213
1852900ce9ea doc/TIFFS write-up
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diff changeset
214 All of the above are common and well-known principles, successfully implemented
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
215 in well-known flash file systems such as JFFS2 in Linux. TIFFS is absolutely
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diff changeset
216 no different in this regard; for the implementation details, read the source
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diff changeset
217 code.
1852900ce9ea doc/TIFFS write-up
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diff changeset
218
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diff changeset
219 How this FFS comes into being
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diff changeset
220 =============================
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diff changeset
221
1852900ce9ea doc/TIFFS write-up
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diff changeset
222 (This section is only relevant to you if you plan on physically producing your
1852900ce9ea doc/TIFFS write-up
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diff changeset
223 own GSM phones or modems on your own factory production line, like this author
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
224 fancies doing in the not-too-distant future, or if you simply enjoy knowing
1852900ce9ea doc/TIFFS write-up
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents: 224
diff changeset
225 how it is done.)
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parents: 224
diff changeset
226
1852900ce9ea doc/TIFFS write-up
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diff changeset
227 To my knowledge, TI never used or produced a tool akin to mkfs.jffs2 in the
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parents: 224
diff changeset
228 embedded Linux world, which would produce a TIFFS image complete with some
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
229 initial directory and file content "in vitro". Instead it appears that the FFS
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parents: 224
diff changeset
230 instances found in shipped products such as Openmoko phones have been created
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diff changeset
231 "in vivo" by TI's firmware running on the device itself during the "production
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diff changeset
232 test" phase.
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diff changeset
233
1852900ce9ea doc/TIFFS write-up
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diff changeset
234 The process seems to go like this:
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diff changeset
235
1852900ce9ea doc/TIFFS write-up
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diff changeset
236 * When the printed circuit board is physically populated with components such
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diff changeset
237 as the Calypso chip and the flash chip, the latter can be blank - if the
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parents: 224
diff changeset
238 board design has the nIBOOT pin pulled low, enabling the Calypso boot ROM
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parents: 224
diff changeset
239 (Openmoko and Pirelli both good on this one, but shame on Compal!), there is
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parents: 224
diff changeset
240 no need to preprogram the flash chip with anything prior to populating it on
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parents: 224
diff changeset
241 the board, and the device remains fully unbrickable at all times afterward.
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diff changeset
242
1852900ce9ea doc/TIFFS write-up
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diff changeset
243 * When the assembled board is powered up for the first time, with completely
1852900ce9ea doc/TIFFS write-up
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diff changeset
244 blank flash, the Calypso boot ROM will sit there and patiently wait for a
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parents: 224
diff changeset
245 code download on either of its two UARTs.
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diff changeset
246
1852900ce9ea doc/TIFFS write-up
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diff changeset
247 * Using TI's FLUID (Flash Loader Utility Independent of Device) or FreeCalypso's
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diff changeset
248 fc-loadtool free replacement, the factory production station loads the main
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diff changeset
249 firmware image into the flash. Note, it is just the firmware image at this
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diff changeset
250 step, and the FFS sectors remain blank.
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diff changeset
251
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diff changeset
252 * The board is commanded to reboot (or power-cycled), and the firmware image
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diff changeset
253 boots for the first time.
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diff changeset
254
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diff changeset
255 * TI's FFS implementation code in their standard firmware reacts to all blank
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256 flash in the FFS sectors as follows: it performs what they call the preformat
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257 operation, writing the TIFFS signature and a BF state byte into every FFS
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258 sector, but the main "format" operation, which sets up the AB/BD block roles,
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259 creates the root inode and makes the FFS ready to accept the creation of its
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diff changeset
260 first directories and files, is not done automatically.
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261
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diff changeset
262 In order to perform the FFS format operation and then fill the new FFS with
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diff changeset
263 whatever directories and files are deemed needed to be present in "fresh"
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
264 shipping products, the factory production station connects to the just-booted
1852900ce9ea doc/TIFFS write-up
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diff changeset
265 firmware running on the target via the RVT/ETM protocol (see the RVTMUX
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266 write-up), and sends "test mode" commands to this running firmware. These
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diff changeset
267 "FFS test mode" (or TMFFS) commands include the format operation, an mkdir
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diff changeset
268 operation to create directories, and a "file write" operation akin to doing
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diff changeset
269 'cat > /dir/whatever/file', creating files in FFS and storing any desired data
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diff changeset
270 in them.
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271
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272 The IMEI is assigned and written into FFS in this process, but it is not the
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diff changeset
273 only data item that will be unique for each individual device made. Much more
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parents: 224
diff changeset
274 important are the RF calibration values: I have yet to learn exactly what is
1852900ce9ea doc/TIFFS write-up
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diff changeset
275 being (or needs to be) measured, how these measurements are performed (under
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diff changeset
276 what conditions; what external test equipment is needed), and how these measured
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parents: 224
diff changeset
277 and recorded RF calibration values affect GSM device operation, but this TI
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278 presentation gives some clues:
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279
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280 ftp://ftp.ifctf.org/pub/GSM/Calypso/rf_calibration.pdf
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281
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diff changeset
282 All of these calibration values are stored in a bunch of files under the
1852900ce9ea doc/TIFFS write-up
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283 /gsm/rf subtree, and these files seem to be "owned" by the L1 code. The latter
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284 has RAM data structures which correspond to these files; upon normal boot the
1852900ce9ea doc/TIFFS write-up
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diff changeset
285 initialization code looks in FFS, and if it finds any of the RF calibration
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
286 files, it reads each present file into the corresponding RAM data structure,
1852900ce9ea doc/TIFFS write-up
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diff changeset
287 overwriting the compiled-in defaults. It appears (slightly uncertain because I
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288 have not yet reintegrated the code in question into our own gsm-fw) that the RF
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
289 calibration files in FFS come into being as follows:
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290
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diff changeset
291 * The RF calibration code in L1 (i.e., part of the main GSM fw) performs the
1852900ce9ea doc/TIFFS write-up
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diff changeset
292 measurements and stores results in its RAM data structures as commanded by
1852900ce9ea doc/TIFFS write-up
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diff changeset
293 the production test station through the "test mode" interface;
1852900ce9ea doc/TIFFS write-up
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diff changeset
294
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295 * A final test mode command directs the above L1 code to write its RAM data
1852900ce9ea doc/TIFFS write-up
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296 structures into FFS.
1852900ce9ea doc/TIFFS write-up
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297
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diff changeset
298 Once I actually learn this RF calibration process properly in connection with
1852900ce9ea doc/TIFFS write-up
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diff changeset
299 building my own Calypso-based GSM "dumbphone", I'll be able to say exactly what
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
300 it would take to recreate these RF calibration values if they are lost. But
1852900ce9ea doc/TIFFS write-up
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diff changeset
301 until then the only advice I can give is to make a backup copy of your modem
1852900ce9ea doc/TIFFS write-up
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diff changeset
302 FFS with fc-loadtool, and to save it securely.
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diff changeset
303
430
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diff changeset
304 Compal and Pirelli differences
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diff changeset
305 ==============================
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306
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307 The above description refers to TI's vanilla reference version, and it seems
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308 like Openmoko (FIC) was the only phone/modem manufacturer who followed it
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diff changeset
309 without major deviations. In contrast, both Compal (Mot C1xx) and Foxconn
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310 (Pirelli DP-L10) moved the vital per-unit factory data (IMEI and RF calibration)
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
311 out of the FFS into their own ad hoc flash data structures (which are very
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diff changeset
312 difficult to reverse-engineer and make use of, unfortunately), leaving their FFS
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diff changeset
313 only for less critical data.
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314
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315 In Compal's case (at least on the C139 model with which I have extensive
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diff changeset
316 personal experience) the FFS stores only users' personal information and nothing
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317 more. One can turn the phone off, use fc-loadtool to erase the FFS sectors, and
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
318 boot the regular fw back up; the fw will automatically do a new FFS format (it
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diff changeset
319 even displays a message on the LCD as it does so) and carry on happily as a
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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diff changeset
320 "fresh" or "blank", perfectly functional and usable phone.
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321
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diff changeset
322 In Pirelli's case, booting their official fw with blank FFS sectors will also
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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diff changeset
323 result in the FFS being automatically formatted, but their fw expects some
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
324 static "asset" files to be present in this FFS: UI graphics and language
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
325 strings, ringtones, firmware images for the WiFi and VoIP processors and some
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
326 static configuration files, about 3 MiB in total. Thus although the firmware
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diff changeset
327 will auto-format the blank FFS sectors, it won't function normally with all of
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
328 these "asset" files missing. Foxconn's original factory production line station
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
329 must have uploaded these files to each phone via the TMFFS2 protocol, and our
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parents: 250
diff changeset
330 FreeCalypso suite now features a tool that can replicate this feat: fc-fsio.
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parents: 250
diff changeset
331
227
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diff changeset
332 FreeCalypso support for TIFFS
1852900ce9ea doc/TIFFS write-up
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diff changeset
333 =============================
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diff changeset
334
250
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diff changeset
335 Aside from implementing and using it in our own gsm-fw, FreeCalypso offers
227
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diff changeset
336 the following support for TIFFS:
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diff changeset
337
250
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338 1. We have a utility for "in vitro" examination of FFS images read out of GSM
3d88461d8284 beginning of TIFFS IVA documentation
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parents: 227
diff changeset
339 devices with fc-loadtool. This tiffs utility (along with mokoffs and pirffs
3d88461d8284 beginning of TIFFS IVA documentation
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diff changeset
340 wrappers) lives in the ffstools top-level directory of the freecalypso-sw
3d88461d8284 beginning of TIFFS IVA documentation
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parents: 227
diff changeset
341 source tree. This TIFFS "in vitro analyzer" utility supplants the earlier
3d88461d8284 beginning of TIFFS IVA documentation
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parents: 227
diff changeset
342 mpffs-* tools, and adds some additional examination functionality. It is
3d88461d8284 beginning of TIFFS IVA documentation
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parents: 227
diff changeset
343 strictly a "read only" tool, however - it is not designed for "in vitro"
430
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parents: 250
diff changeset
344 editing of TIFFS images.
227
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diff changeset
345
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diff changeset
346 2. A number of FC tools may be strung together into a kit for editing the FFS
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
347 content of a GSM device, e.g., for changing the IMEI. The following pieces
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diff changeset
348 will be involved:
1852900ce9ea doc/TIFFS write-up
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diff changeset
349
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diff changeset
350 * What is destined to eventually become our totally free GSM fw (the gsm-fw
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
351 source subtree at the top of freecalypso-sw) does not contain any of the
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
352 actual GSM protocol stack (or even L1) functionality yet, but it already
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
353 contains both the FFS code and those components (ETM and TMFFS[12]) which
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
354 are needed for interfacing an external "test mode shell" to this FFS
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
355 implementation through the RVTMUX interface. And when our gsm-fw does gain
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
356 the actual GSM functionality, the ability to build a minimal FFS+ETM-only
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
357 configuration will still be retained.
1852900ce9ea doc/TIFFS write-up
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diff changeset
358
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diff changeset
359 * The minimal FFS+ETM subset of gsm-fw can be built into a ramImage (runs
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
360 entirely from RAM via fc-xram, no flashing), and run on a physical device
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
361 such as the GTA0x GSM modem via the fc-xram host utility;
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parents: 224
diff changeset
362
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parents: 224
diff changeset
363 * After loading the ramImage, fc-xram will immediately exec our rvinterf host
430
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parents: 250
diff changeset
364 utility (see rvinterf/README);
227
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diff changeset
365
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diff changeset
366 * Once the GSM device is running what is effectively an FFS editing agent out
430
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parents: 250
diff changeset
367 of RAM, accessed via rvinterf over the serial channel, the user can run
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
368 fc-tmsh or fc-fsio, and this "test mode shell" provides commands for writing
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
369 things to FFS exactly like one would do in the factory production line
14618bd924ec doc/RVTMUX and doc/TIFFS-Overview: updates
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parents: 250
diff changeset
370 environment for which TI taylored their tools.
227
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diff changeset
371
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
372 The "in vivo" method of editing the FFS content of a GSM device described above
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
373 will probably sound very convoluted, and you may find yourself asking for a way
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
374 to do it "in vitro" instead: read the FFS out of flash with fc-loadtool, edit
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
375 that image "in vitro" with some utility on your PC, and then use fc-loadtool
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
376 again to program it back into your device. But consider that an "in vitro" FFS
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
377 modification would involve erasing and rewriting all sectors of your FFS,
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
378 whereas an "in vivo" modification of some small file like the IMEI would be
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
379 just a short flash write operation without any erasures at all, i.e., kinder
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
380 on the flash.
1852900ce9ea doc/TIFFS write-up
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parents: 224
diff changeset
381
430
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parents: 250
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382 In any case, the "in vivo" method is already available now because all of the
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383 components involved therein are also needed for other development uses in the
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384 FreeCalypso project, whereas developing a fully-functional "in vitro"
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385 alternative (one that can create an FFS image "de novo" from a tree of files
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386 and directories a la mkfs.jffs2, or add new files to an existing TIFFS image
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387 etc) would be a good amount of extra work which we otherwise don't need - hence
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388 the latter is not very likely to be written any time soon.
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389
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390 However, if the "in vitro" modification you seek is something trivial like
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391 changing the byte content of a file such as /pcm/IMEI or /gsm/com/rfcap without
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392 changing its length, you can use the existing "in vitro, read-only" tiffs host
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393 utility to find the exact byte location of the file data within the TIFFS image,
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394 and then use your favourite hex editor to whack whatever new byte content you
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395 like at that offset.