On Sat, 15 Oct 2011, Johannes Stezenbach wrote: > What I meant to say is Markus' statement that the device only > works at a certain transfer size cannot be true since > this size is not visible to the device via the USB bus. That's what I would expect, too. But did you take a look at the usbmon traces Markus acquired? http://marc.info/?l=linux-usb&m=131845614819045&w=2 They aren't completely definitive because the communications between the computer and the device _before_ the bulk transfers started were different. However they do clearly show the device working with 24064-byte transfers and not working with 12288+11776-byte transfers. > If you queue two URBs, one 12288 and 11776 bytes, the device > does not see any difference to one URB with 24064. It's just not > in the USB wire protocol. You can argue until you're blue in the face. It won't affect the results that Markus got in real life. > It would make a difference if the > device violated the spec and sent 188 byte packets. However, the > spec says a short packet terminates the transfer. But I wonder > if this is really the case? The device does not send short packets. If it did, the 24064-byte transfers would end early. 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
