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

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

	hello.  Continuing this thread, I believe I've asked this question
before, but I don't think I've been as specific aboutit.

	How should I go about generating a zero length packet through our USB
stack?  It looks like you can just send a 0 length usb transfer down the
FreeBSD stack, and Darwin and Linux have ioctls to accomplish this task.
When I send a zero-length transfer down the NetBSD stak, I get panics in
the uhci(4) and ehci(4) drivers.  Specifically, the chain allocators get
confused about the fact that the lengths of the xfer are zero.  Apple
devices need to receive such transfers in order to operate, so I'd like to
figure out how to add this support if it isn't already there.  I think it
will work if I can figure out what I need to do to teach the uhci(4),
ehci(4) and ohci(4) drivers how to deal with this condition.   Is there any
documentation on how these chain allocators work?

Any thoughts would be greatly appreciated.
-thanks
-Brian