Re: XP USB driver stack/lost bytes on bulk transfer

From: Alexander Grigoriev (alegr_at_earthlink.net)
Date: 01/13/05 

Date: Thu, 13 Jan 2005 08:14:26 -0800

I think there is another bug in the scanner's firmware that causes it to
lose data that cannot be transferred fast enough.

64 bytes per transfer will give you 64 kbytes/s, which is too little for
most good scanners.

"bench" <ruh@keba.co.at> wrote in message
news:ad44867b.0501130204.35c548c9@posting.google.com...
> Hello
>
> I loose bytes ( some multiple of 64 bytes ( =MaxPacketSize ) ) with
> Windows XP SP1 on a Gibabyte PC 566 MHz ( single CPU ) with a VIA
> chipset ( USB 1.1 HC ).
>
> The following happens:
> My USB device driver sends 'read' urbs down the stack ( reading a
> picture ~1.5MB from scanner ). USBD_SHORT_TRANSFER_OK ist set and
> MaximumTransferSize ist default ( 4KB ).
> If i read the image with
> urb->UrbBulkOrInterruptTransfer.TransferBufferLength=64 bytes, some 64
> byte-packets get lost in lower drivers.
> When TransferBufferLength is set on some higher value ( multiple of 64
> ) the image is transfered correctly.
>
> Tests:
> Tested some ( faster ) ASUS pcs with Intel chipset -> No problems.
> Downloaded and installed the latest USB hotfix -> No changes.
> Wrote a filter driver 'lower' my driver -> Yes, bytes get lost when
> requesting 64 bytes.
> Wrote a 'HC debug driver' permanent checking the HC registers -> HC
> never reports errors ( did not check transfer descriptors ).
> Counted bytes on USB analyzer -> The whole image is transferred.
> Activated debug outputs in my driver -> OK, also when
> TransferBufferLength=64!
> Changed internal flowings in my usb driver to be faster -> Bytes get
> lost on TransferBufferLength=64 AND TransferBufferLength=128 ( OK, on
> higher values )!
> Tested my own NT and OS/2 drivers on that motherboard ( the image is
> transferred twice faster than under XP ) -> OK.
> Used checked build versions of the XP usb drivers -> did not see any
> errors reported in windbg, but i'm not very experienced in that.
>
> I know, that VIA has ( maybe had? ) some special 'features'
> implemented in USB ( in contrast to Intel ), but for me it looks like
> a bug in the XP USB driver stack; maybe some 'timing issue' ( the
> faster the usb device driver, the more bytes it must request each
> urb!? ).
>
> Any ideas?
>
> Thank you,
> Bernhard Ruhsam
>
> PS: The reason, why i have to request just 64 bytes is, that there's a
> bug in the firmware of the scanner, which does not send zero length
> packets.

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