Increase MaxTransferSize of a USB bulk end point

NTDEV
1

The default MaxTransferSize for a USB bulk endpoint set on a Win2K
machine was 4K when I checked with my driver. I know of the WDM way to
increase this size but is there a KMDF way to do it. I searched through
the archives of NTDEV, the usenet… I could see only one similar
unanswered query on Doron’s blog - Have nobody else had such a
requirement before?

–
Vijairaj

2

You must create the select config URB yourself, set MaxTransferSize for each endpoint, use WDF_USB_DEVICE_SELECT_CONFIG_PARAMS_INIT_URB() and then call WdfUsbTargetDeviceSelectConfig()

d
-----Original Message-----
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of xxxxx@gmail.com
Sent: Tuesday, November 06, 2007 9:15 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Increase MaxTransferSize of a USB bulk end point

The default MaxTransferSize for a USB bulk endpoint set on a Win2K
machine was 4K when I checked with my driver. I know of the WDM way to
increase this size but is there a KMDF way to do it. I searched through
the archives of NTDEV, the usenet… I could see only one similar
unanswered query on Doron’s blog - Have nobody else had such a
requirement before?

–
Vijairaj

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3

Vijairaj R wrote:

The default MaxTransferSize for a USB bulk endpoint set on
a Win2K machine was 4K when I checked with my driver. I
know of the WDM way to increase this size but is there a
KMDF way to do it.

Just out of curiosity, how high do you intend to go with your transfer size, and why?

4

Thanks Doron,

Chris, The default will be 4K+32 bytes but it can go up to 12K. Since
it’s only a little bigger than the default value, I don’t want to handle
the packet splitting and reassembly logics.

5

Vijariaj R wrote:

Chris, The default will be 4K+32 bytes but it can go up to 12K.
Since it’s only a little bigger than the default value, I don’t want
to handle the packet splitting and reassembly logics.

4K + 32 bytes? Hope your endpoint packet size divides cleanly into 32.

People have consistently reported problems using bulk URBs much larger than that, so fair warning I suppose, although I don’t think you’ll see much trouble with a value of 12K.