Message-ID: <4BD5CF3C.9020406@draisberghof.de>
Date: Mon, 26 Apr 2010 19:37:00 +0200
From: Josua Dietze <digidietze@draisberghof.de>
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To: =?UTF-8?B?TWljaGHFgiBOYXphcmV3aWN6?= <m.nazarewicz@samsung.com>
CC: Daniel Mack <daniel@caiaq.de>, Marek Szyprowski <m.szyprowski@samsung.com>,
       linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
       Kyungmin Park <kyungmin.park@samsung.com>
Subject: Re: USB gadget with drivers "on board"
References: <op.vbrfqdznfxrvh1@pikus> <20100426141605.GO30801@buzzloop.caiaq.de> <op.vbrxsrw07p4s8u@pikus> <20100426145700.GP30801@buzzloop.caiaq.de> <op.vbr0prfb7p4s8u@pikus>
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Michał Nazarewicz schrieb:

> On Mon, 26 Apr 2010 16:16:05 +0200, Daniel Mack <daniel@caiaq.de> wrote:
>> Are you sure they don't do exactly that by running two interfaces in
>> the same configuration?
> 
> Yes, I'm sure.  I've investigated an USB GSM modem which, when plugged
> for the first time reports as mass storage (single configuration, single
> interface) and when drivers are installed as a full blown composite
> gadget.  I still haven't figured out how it does that.


These are the notorious mode switching devices. In Windows, they 
obviously install a special storage driver doing one specific action 
on each following plugging.
This action - some storage or control command - will "flip" the 
device, making it "disconnect" and returning as a completely different 
composite device.

Storage commands used for this procedure range from "SCSI rezero" over 
"passthrough" to "SCSI eject", or involve vendor specific stuff.


Josua Dietze

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