On Thu, 2004-07-22 at 14:39, Alan Stern wrote:
> I don't know whether the patch I sent will really work. There's a problem
> with the initial 64-byte get_descriptor and it's not clear how Windows
> works around it. The problem is that after the device sends its first
> 8-byte packet and is ready to send the next one, the host thinks the short
> packet indicates the end of the response. So the host will send an OUT
> packet for the status stage of the transfer but the device will expect to
> get another IN packet. If the device responds with an ACK to the OUT then
> all is well, but otherwise the transfer will fail. Maybe the host doesn't
> care if the transfer fails; maybe it only checks to see that the first 8
> bytes were transferred okay.
I needed a check for this when working on the national 9604 gadget
driver. The National chip only has an 8 byte fifo on end point 0.
Until the device is in the configured state I had to change wLength to
8, if I read a greater value. I haven't checked the USB spec. but I
think there is probably some logic behind MS's thinking and this is how
things are supposed to work.
David
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