1 ============================== 2 Multifunction Composite Gadget 3 ============================== 4 5 Overview 6 ======== 7 8 The Multifunction Composite Gadget (or g_multi) is a composite gadget 9 that makes extensive use of the composite framework to provide 10 a... multifunction gadget. 11 12 In its standard configuration it provides a single USB configuration 13 with RNDIS[1] (that is Ethernet), USB CDC[2] ACM (that is serial) and 14 USB Mass Storage functions. 15 16 A CDC ECM (Ethernet) function may be turned on via a Kconfig option 17 and RNDIS can be turned off. If they are both enabled the gadget will 18 have two configurations -- one with RNDIS and another with CDC ECM[3]. 19 20 Please note that if you use non-standard configuration (that is enable 21 CDC ECM) you may need to change vendor and/or product ID. 22 23 Host drivers 24 ============ 25 26 To make use of the gadget one needs to make it work on host side -- 27 without that there's no hope of achieving anything with the gadget. 28 As one might expect, things one need to do very from system to system. 29 30 Linux host drivers 31 ------------------ 32 33 Since the gadget uses standard composite framework and appears as such 34 to Linux host it does not need any additional drivers on Linux host 35 side. All the functions are handled by respective drivers developed 36 for them. 37 38 This is also true for two configuration set-up with RNDIS 39 configuration being the first one. Linux host will use the second 40 configuration with CDC ECM which should work better under Linux. 41 42 Windows host drivers 43 -------------------- 44 45 For the gadget to work under Windows two conditions have to be met: 46 47 Detecting as composite gadget 48 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 49 50 First of all, Windows need to detect the gadget as an USB composite 51 gadget which on its own have some conditions[4]. If they are met, 52 Windows lets USB Generic Parent Driver[5] handle the device which then 53 tries to match drivers for each individual interface (sort of, don't 54 get into too many details). 55 56 The good news is: you do not have to worry about most of the 57 conditions! 58 59 The only thing to worry is that the gadget has to have a single 60 configuration so a dual RNDIS and CDC ECM gadget won't work unless you 61 create a proper INF -- and of course, if you do submit it! 62 63 Installing drivers for each function 64 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 65 66 The other, trickier thing is making Windows install drivers for each 67 individual function. 68 69 For mass storage it is trivial since Windows detect it's an interface 70 implementing USB Mass Storage class and selects appropriate driver. 71 72 Things are harder with RDNIS and CDC ACM. 73 74 RNDIS 75 ..... 76 77 To make Windows select RNDIS drivers for the first function in the 78 gadget, one needs to use the [[file:linux.inf]] file provided with this 79 document. It "attaches" Window's RNDIS driver to the first interface 80 of the gadget. 81 82 Please note, that while testing we encountered some issues[6] when 83 RNDIS was not the first interface. You do not need to worry abut it 84 unless you are trying to develop your own gadget in which case watch 85 out for this bug. 86 87 CDC ACM 88 ....... 89 90 Similarly, [[file:linux-cdc-acm.inf]] is provided for CDC ACM. 91 92 Customising the gadget 93 ...................... 94 95 If you intend to hack the g_multi gadget be advised that rearranging 96 functions will obviously change interface numbers for each of the 97 functionality. As an effect provided INFs won't work since they have 98 interface numbers hard-coded in them (it's not hard to change those 99 though[7]). 100 101 This also means, that after experimenting with g_multi and changing 102 provided functions one should change gadget's vendor and/or product ID 103 so there will be no collision with other customised gadgets or the 104 original gadget. 105 106 Failing to comply may cause brain damage after wondering for hours why 107 things don't work as intended before realising Windows have cached 108 some drivers information (changing USB port may sometimes help plus 109 you might try using USBDeview[8] to remove the phantom device). 110 111 INF testing 112 ........... 113 114 Provided INF files have been tested on Windows XP SP3, Windows Vista 115 and Windows 7, all 32-bit versions. It should work on 64-bit versions 116 as well. It most likely won't work on Windows prior to Windows XP 117 SP2. 118 119 Other systems 120 ------------- 121 122 At this moment, drivers for any other systems have not been tested. 123 Knowing how MacOS is based on BSD and BSD is an Open Source it is 124 believed that it should (read: "I have no idea whether it will") work 125 out-of-the-box. 126 127 For more exotic systems I have even less to say... 128 129 Any testing and drivers *are* *welcome*! 130 131 Authors 132 ======= 133 134 This document has been written by Michal Nazarewicz 135 ([[mailto:mina86@mina86.com]]). INF files have been hacked with 136 support of Marek Szyprowski ([[mailto:m.szyprowski@samsung.com]]) and 137 Xiaofan Chen ([[mailto:xiaofanc@gmail.com]]) basing on the MS RNDIS 138 template[9], Microchip's CDC ACM INF file and David Brownell's 139 ([[mailto:dbrownell@users.sourceforge.net]]) original INF files. 140 141 Footnotes 142 ========= 143 144 [1] Remote Network Driver Interface Specification, 145 [[https://msdn.microsoft.com/en-us/library/ee484414.aspx]]. 146 147 [2] Communications Device Class Abstract Control Model, spec for this 148 and other USB classes can be found at 149 [[http://www.usb.org/developers/devclass_docs/]]. 150 151 [3] CDC Ethernet Control Model. 152 153 [4] [[https://msdn.microsoft.com/en-us/library/ff537109(v=VS.85).aspx]] 154 155 [5] [[https://msdn.microsoft.com/en-us/library/ff539234(v=VS.85).aspx]] 156 157 [6] To put it in some other nice words, Windows failed to respond to 158 any user input. 159 160 [7] You may find [[http://www.cygnal.org/ubb/Forum9/HTML/001050.html]] 161 useful. 162 163 [8] https://www.nirsoft.net/utils/usb_devices_view.html 164 165 [9] [[https://msdn.microsoft.com/en-us/library/ff570620.aspx]]
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