On Thu, Jul 17, 2014 at 7:55 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > I can't say this is actually wrong, but have you ever encountered a > situation where this would be needed? How often does anyone need to do > a multi-packet transfer over an interrupt endpoint? > Hi Alan, I did some testing with multi interrupt transfers some time ago. You can get allocated a guaranteed 3x1024 time slot per uframe for an interval of your choice on usb 2.0. So zlps are needed to send exactly 1024 or 2048 bytes in that time slot. Also, interrupt transfers are crc checked and resent (as long as uframe time is still available). So you get guaranteed timing like iso sends, and guaranteed data like bulk sends. This could be valuable for time sensitive apps with known data capacities. Microsoft only started supporting multi-interrupt transfers in Windows Vista and beyond. Winxp refuses to die, so probably no one has built an actual hardware device for consumers that uses multi-interrupt xfers up to now. Regards, Steve -- 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
