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Michal Nazarewicz
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Greg Kroah-Hartman
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-*- org -*- | ||
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* Overview | ||
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The Multifunction Composite Gadget (or g_multi) is a composite gadget | ||
that makes extensive use of the composite framework to provide | ||
a... multifunction gadget. | ||
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In it's standard configuration it provides a single USB configuration | ||
with RNDIS[1] (that is Ethernet), USB CDC[2] ACM (that is serial) and | ||
USB Mass Storage functions. | ||
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A CDC ECM (Ethernet) function may be turned on via a Kconfig option | ||
and RNDIS can be turned off. If they are both enabled the gadget will | ||
have two configurations -- one with RNDIS and another with CDC ECM[3]. | ||
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Please not that if you use non-standard configuration (that is enable | ||
CDC ECM) you may need to change vendor and/or product ID. | ||
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* Host drivers | ||
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To make use of the gadget one needs to make it work on host side -- | ||
without that there's no hope of achieving anything with the gadget. | ||
As one might expect, things one need to do very from system to system. | ||
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** Linux host drivers | ||
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Since the gadget uses standard composite framework and appears as such | ||
to Linux host it does not need any additional drivers on Linux host | ||
side. All the functions are handled by respective drivers developed | ||
for them. | ||
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This is also true for two configuration set-up with RNDIS | ||
configuration being the first one. Linux host will use the second | ||
configuration with CDC ECM which should work better under Linux. | ||
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** Windows host drivers | ||
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For the gadget two work under Windows two conditions have to be met: | ||
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*** Detecting as composite gadget | ||
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First of all, Windows need to detect the gadget as an USB composite | ||
gadget which on its own have some conditions[4]. If they are met, | ||
Windows lets USB Generic Parent Driver[5] handle the device which then | ||
tries to much drivers for each individual interface (sort of, don't | ||
get into too many details). | ||
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The good news is: you do not have to worry about most of the | ||
conditions! | ||
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The only thing to worry is that the gadget has to have a single | ||
configuration so a dual RNDIS and CDC ECM gadget won't work unless you | ||
create a proper INF -- and of course, if you do submit it! | ||
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*** Installing drivers for each function | ||
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The other, trickier thing is making Windows install drivers for each | ||
individual function. | ||
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For mass storage it is trivial since Windows detect it's an interface | ||
implementing USB Mass Storage class and selects appropriate driver. | ||
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Things are harder with RDNIS and CDC ACM. | ||
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**** RNDIS | ||
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To make Windows select RNDIS drivers for the first function in the | ||
gadget, one needs to use the [[file:linux.inf]] file provided with this | ||
document. It "attaches" Window's RNDIS driver to the first interface | ||
of the gadget. | ||
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Please note, that while testing we encountered some issues[6] when | ||
RNDIS was not the first interface. You do not need to worry abut it | ||
unless you are trying to develop your own gadget in which case watch | ||
out for this bug. | ||
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**** CDC ACM | ||
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Similarly, [[file:linux-cdc-acm.inf]] is provided for CDC ACM. | ||
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**** Customising the gadget | ||
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If you intend to hack the g_multi gadget be advised that rearranging | ||
functions will obviously change interface numbers for each of the | ||
functionality. As an effect provided INFs won't work since they have | ||
interface numbers hard-coded in them (it's not hard to change those | ||
though[7]). | ||
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This also means, that after experimenting with g_multi and changing | ||
provided functions one should change gadget's vendor and/or product ID | ||
so there will be no collision with other customised gadgets or the | ||
original gadget. | ||
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Failing to comply may cause brain damage after wondering for hours why | ||
things don't work as intended before realising Windows have cached | ||
some drivers information (changing USB port may sometimes help plus | ||
you might try using USBDeview[8] to remove the phantom device). | ||
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**** INF testing | ||
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Provided INF files have been tested on Windows XP SP3, Windows Vista | ||
and Windows 7, all 32-bit versions. It should work on 64-bit versions | ||
as well. It most likely won't work on Windows prior to Windows XP | ||
SP2. | ||
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** Other systems | ||
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At this moment, drivers for any other systems have not been tested. | ||
Knowing how MacOS is based on BSD and BSD is an Open Source it is | ||
believed that it should (read: "I have no idea whether it will") work | ||
out-of-the-box. | ||
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For more exotic systems I have even less to say... | ||
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Any testing and drivers *are* *welcome*! | ||
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* Authors | ||
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This document has been written by Michal Nazarewicz | ||
([[mailto:mina86@mina86.com]]). INF files have been hacked with | ||
support of Marek Szyprowski ([[mailto:m.szyprowski@samsung.com]]) and | ||
Xiaofan Chen ([[mailto:xiaofanc@gmail.com]]) basing on the MS RNDIS | ||
template[9], Microchip's CDC ACM INF file and David Brownell's | ||
([[mailto:dbrownell@users.sourceforge.net]]) original INF files. | ||
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* Footnotes | ||
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[1] Remote Network Driver Interface Specification, | ||
[[http://msdn.microsoft.com/en-us/library/ee484414.aspx]]. | ||
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[2] Communications Device Class Abstract Control Model, spec for this | ||
and other USB classes can be found at | ||
[[http://www.usb.org/developers/devclass_docs/]]. | ||
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[3] CDC Ethernet Control Model. | ||
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[4] [[http://msdn.microsoft.com/en-us/library/ff537109(v=VS.85).aspx]] | ||
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[5] [[http://msdn.microsoft.com/en-us/library/ff539234(v=VS.85).aspx]] | ||
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[6] To put it in some other nice words, Windows failed to respond to | ||
any user input. | ||
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[7] You may find [[http://www.cygnal.org/ubb/Forum9/HTML/001050.html]] | ||
useful. | ||
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[8] http://www.nirsoft.net/utils/usb_devices_view.html | ||
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[9] [[http://msdn.microsoft.com/en-us/library/ff570620.aspx]] |
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