On Wed, 20 Dec 2006, Phil Endecott wrote: > Dear USB Experts, > > I have a Net2280 PCI card and I'm trying to get the gadgetfs user-mode > test program from http://www.linux-usb.org/gadget/usb.c to work. > There's a second Linux box at the other end of the USB cable and both > ends are running 2.6.19. I have encountered a problem which I think > could be a bug in the net2280 driver - though I suppose it's more likely > that I just don't understand it properly yet. > > The test program sends descriptors to gadgetfs. The two ends CONNECT. > The host asks for descriptors, and those that the kernel knows about > itself are sent OK. Then the host asks for a string descriptor. > This is the responsibility of the test program. Gadgetfs delegates > this request to userspace. > > From here on the exact behaviour varies from one run to the next. > I think it is sensitive to how quickly the test program returns the > string descriptor data. Certainly running the test program under > strace slows it down enough to change the behaviour. However, much > of the time I believe that the Net2280 chip generates an interrupt > saying "ep0 IN fifo empty, data required" before the test program > has provided the string data for it to send. > > As I understand it, at this point the driver should NOT write > anything to the fifo and the hardware should NAK. Eventually the > test program would supply the string descriptor data and this > would be returned to the host. But this doesn't seem to be what > happens. It looks as if the hardware returns a ZLP immediately. > The host isn't satisfied with this, and looking at the host-end > code it retries a few times, then tries again asking for only 2 > bytes (there's a comment about broken devices), and eventually > gives up.
This has been fixed in the current development kernels (-mm or Greg KH's development patch series). Here is the patch: http://marc.theaimsgroup.com/?l=linux-usb-devel&m=116369017318210&w=2 Alan Stern ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
