Re: Potential problem with reading data from usb devices with ugen(4)

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	hello greg.  I've been trying to keep the noise on this thread to a
minimum, but it appears I mis-wrote about what happens when trying to
generate zero-length packets. The state of my re-worked ugen(4) is much
more stable and I have installed some additional diagnostics to determine
what is going on with this issue.
With that in mind, here is where things stand:

With ehci(4), when I try to send a zero-length packet, I get the error:
USBD_NOMEM back from the usbd_transfer() call.

with uhci(4), all now works as expected.   I get the call to the callback
function and data moves up and down the USB stack as expected.

	To answer your question about whether there is a standard for
generating these packets, it seems there is not.  Linux expects you to use
an ioctl() to generate the packet while FreeBSD expects you to send a write
request with 0 bytes, as we do with the ugen(4) changes I'm making.



-thanks
-Brian