On 2013.05.30 14:44, Toby Gray wrote: > The current libusbx windows backend deliberately turns off sending a ZLP > at the end of a transfer: > https://github.com/libusbx/libusbx/blob/master/libusb/os/windows_usb.c#L2651 > It's the disabling of the SHORT_PACKET_TERMINATE: > http://msdn.microsoft.com/en-us/library/windows/hardware/ff728833(v=vs.85).aspx > <http://msdn.microsoft.com/en-us/library/windows/hardware/ff728833%28v=vs.85%29.aspx> > > This comes from > https://github.com/libusbx/libusbx/commit/578c50c99646e5ebbcfbea653524a519b843ebcd > but that's really just a move of code submitted here: > https://github.com/libusbx/libusbx/commit/9a4249f8a104b98a15a7e3ba7ecae9a385ed9027 > > So it looks like the Windows backend has always done it. > > Some further reading which might help: > https://sourceforge.net/mailarchive/message.php?msg_id=28120716 > https://sourceforge.net/mailarchive/message.php?msg_id=25571546 > > Linux does support control of if the zero length packet is sent: > https://github.com/libusbx/libusbx/blob/master/libusb/os/linux_usbfs.c#L1699
Thanks, Toby, for doing this search into our archives! > I was going to create a quick patch for this, but it's harder than it > first looks because the policy for WinUSB is per pipe, but on Linux it's > per URB. I think last time we discussed it, the idea was that that we would try to make these kind of settings exposed in a backend configuration API call. In other words, we'd have a libusb_set_backend_setting(...) call that could set parameter such as WINDOWS_BACKEND_SET_ZLP_PIPE or LINUX_BACKEND_SET_ZLP_URB. Now, if you need more granular settings than enabling/disabling global flags, it may be a bit tricky. And then there are the implications for concurrent applications that will want different settings... Regards, /Pete ------------------------------------------------------------------------------ Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET Get 100% visibility into your production application - at no cost. Code-level diagnostics for performance bottlenecks with <2% overhead Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap1 _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
