On Fri, 14 Oct 2011, Johannes Stezenbach wrote: > I don't really want to help Markus with his proprietary, binary-only > userspace driver crap, but I wonder why nobody seems to remember > how the USB protocol works on the wire? I remember it perfectly well. > The transfer size is > never seen by the device, thus it cannot matter if two small URBs > or one large URB are queued. What matters is the packet size. That's what I have been saying. Markus's experience contradicts this, however. > Apparently the device can only handle fixed size packets > of either 188 or 2*188 byte, thus it breaks with 12288 or 11776. No. The device expects 512-byte packets because it uses a bulk endpoint. > The endpoint's wMaxPacketSize might reflect this. For high-speed devices, a bulk endpoint's wMaxPacketSize must always be 512. > I guess a transfer size of e.g. 188*60=11280 would work. > See the first mail of this thread. According to Markus, with this particular device nothing but 24064 works. The discussion is a little difficult to follow because he talked about two different devices without always being clear about which was which. > See also Sergei's comment in > http://lkml.org/lkml/2011/10/12/183 Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
