On Tue, 29 Mar 2005, Jan Merka wrote:
> On Tuesday 29 March 2005 04:16 pm, jklaas wrote:
> > I have another question that I don't quite understand. With the FM Radio
> > the TransferBufferLength in the URB going down is usually either 0x16 or
> > 0xca. The URB coming back has the TransferBufferLength is 0x06. I
> > guess I don't quite understand why they're different.
>
> In one direction (OUT or "goind down" in sniffusb's terminology), the length
> of the buffer depends on the size of the command that you are sending to the
> device. On the way back (IN or "going back"), the size tells how may bytes
> were sent back by the device as a response to the received command. Assuming
> that you don't have a description of those commands, the trick is to figure
> out what they mean (and the responses).
OK, here's a log entry from sniffusb, (the one from snoopypro is
essentially the same):
[1656 ms] UsbSnoop - DispatchAny(eb760610) :
IRP_MJ_INTERNAL_DEVICE_CONTROL
[1656 ms] UsbSnoop - MyDispatchInternalIOCTL(eb761e80) : fdo=81f26030,
Irp=81a94
2e8, IRQL=0
[1656 ms] >>> URB 13 going down >>>
-- URB_FUNCTION_GET_DESCRIPTOR_FROM_DEVICE:
TransferBufferLength = 00000016
TransferBuffer = 81aac9a8
TransferBufferMDL = 00000000
Index = 00000078
DescriptorType = 00000003 (USB_STRING_DESCRIPTOR_TYPE)
LanguageId = 00000409
[1657 ms] UsbSnoop - MyInternalIOCTLCompletion(eb761db0) :
fido=00000000, Irp=81
a942e8, Context=81adafa8, IRQL=2
[1657 ms] <<< URB 13 coming back <<<
-- URB_FUNCTION_CONTROL_TRANSFER:
PipeHandle = 81aebd34
TransferFlags = 00000003 (USBD_TRANSFER_DIRECTION_IN,
USBD_SHORT_TRANSF
ER_OK)
TransferBufferLength = 00000006
TransferBuffer = 81aac9a8
TransferBufferMDL = 81a94268
00000000: 06 03 00 f8 22 c8
UrbLink = 00000000
SetupPacket =
00000000: 80 06 78 03 09 04 16 00
I'm not sure I understand where to find the data for the TransferBuffer
"going down".
>
> This link may give you more insight in reverse engineering a USB device
> driver: http://www.toth.demon.co.uk/usb/reverse-0.2.txt
Yep, he's on version 0.3.
> J.
>
>
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--
James Klaas
The activity of "debugging" or removing bugs from a program ends when a
programmer gets tired of doing it, not when all the bugs are removed.
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