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Date: Thu, 24 Jun 2010 14:22:03 -0400
From: TJ <dimitry.ishenko@gmail.com>
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Subject: Re: [Qemu-devel] Guest OS hangs on usb_add
References: <AANLkTinTVOqbrlyGCwWiD_PrttYyud_EkpMbzCK2wE_O@mail.gmail.com>	<AANLkTila1csfbLt6z-02JriSo1z_7DvK1vylgxn7_kI2@mail.gmail.com>	<AANLkTinEa7pgxPtq2iKS7ETCky_ICI5PubVAWLwcNi0c@mail.gmail.com>
	<4C22E300.5020109@gmail.com> <4C239CF0.4040901@cisco.com>
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To: "David S. Ahern" <daahern@cisco.com>
Cc: qemu-devel@nongnu.org

On 06/24/10 13:59, David S. Ahern wrote:
> 
> 
> On 06/23/10 22:45, TJ wrote:
>>
>>> ---------- Forwarded message ----------
>>> From: Timothy Jones <one.timothy.jones@gmail.com>
>>> Date: Wed, Jun 23, 2010 at 9:07 PM
>>> Subject: Guest OS hangs on usb_add
>>> To: qemu-devel@nongnu.org
>>>
>>>
>>> With some digging around I found out that the qemu hangs in
>>> usb_host_claim_interfaces, which is caused by screwed up usb
>>> descriptor. The device reports the following:
>>>
>>> (gdb) p dev->descr_len
>>> $21 = 50
>>> (gdb) p /x dev->descr[0]@50
>>> $23 = {0x18, 0x1, 0x0, 0x1, 0xff, 0xff, 0xff, 0x8, 0x47, 0x46, 0x0,
>>> 0x30, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x9, 0x2, 0x20,
>>>  0x0, 0x1, 0x1, 0x0, 0x80, 0x19, 0x9, 0x4, 0x0, 0x0, 0x2, 0xff, 0xff,
>>> 0xff, 0x0, 0x7, 0x5, 0x81, 0x2, 0x40, 0x0, 0x0,
>>>  0x7, 0x5, 0x3, 0x2, 0x10, 0x0, 0x0}
>>>
>>> The first 0x18 (Device Descriptor bLength) is supposed to be decimal
>>> 18, not hex! According to USB spec, if the device reports size greater
>>> than expected, the host is supposed ignore the extra bytes. So qemu
>>> behaves correctly here. However, with this length, the following
>>> Configuration Descriptor length falls on a 0x0 and so the qemu spins
>>> in an endless loop. (This is prolly something that should be detected
>>> and reported as error by qemu.)
>>>
>>> My question is: This 0x18 -- is this something that comes from the
>>> device itself (ie, firmware bug)? Or does it come from the USB
>>> subsystem?
> 
> What kind of device is this?
> 
> David
> 

Universal Remote Control MX-950

http://www.universalremote.com/product_detail.php?model=35

-TJ