linux-kernel - Re: [PATCH] USB: output an error message when the pipe type doesn't match the endpoint type

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Message-ID: <AANLkTimCYmyfrvP2-k=cfFbxayP8XWpNZKonRJjNvs6q@mail.gmail.com>
Date:	Tue, 31 Aug 2010 22:04:47 +0800
From:	Xiaofan Chen <xiaofanc@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Clemens Ladisch <clemens@...isch.de>,
	Simon Arlott <simon@...e.lp0.eu>, Greg KH <greg@...ah.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>
Subject: Re: [PATCH] USB: output an error message when the pipe type doesn't
 match the endpoint type

On Tue, Aug 31, 2010 at 9:52 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> On Tue, 31 Aug 2010, Clemens Ladisch wrote:
>
>> Simon Arlott wrote:
>> > Commit f661c6f8c67bd55e93348f160d590ff9edf08904 adds a check of the pipe type if
>> > CONFIG_USB_DEBUG is enabled,
>>
>> I didn't see that commit last year, but wouldn't it break devices like
>> the ESI MIDI Mate whose descriptors want to have low-speed bulk transfers
>> and where the driver has to submit interrupt transfers instead to get it
>> to work at all?
>
> When the kernel sees those invalid low-speed bulk endpoint descriptors,
> it changes its internal copy of the descriptor to interrupt.  Hence
> when the driver submits interrupt URBs, they work correctly.
>

Interesting.

FYI: even though XP/Win2k allow low-speed bulk endpoints, Vista
and Win7 do not allow that.

There are hacks to get around that.
http://www.recursion.jp/avrcdc/lowbulk.html

I took a look at the libusb-win32 source and indeed the author
is using the same trick of submit interrupt URBs.


-- 
Xiaofan
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