On Fri, 15 Apr 2011, Richard Ash wrote: > >> Can anyone explain when a length in usbmon output is not a length, and > >> separately why a device with 64byte max packet size is doing 128 byte > >> reads? > > > > Read the Documentation/usb/usbmon.txt file. Briefly, usbmon's text > > interface displays only the first 32 bytes of each transfer. If you > > want to see the complete data for each transfer, you need to use the > > binary interface. > > Thanks for the clarification, wireshark is installing. > > For the moment I don't need to see packet contents, only the packet > lengths to work out the bit rate. Am I worrying needlessly that a device with > wMaxPacketSize 0x0040 1x 64 bytes > is doing 128 byte reads most of the time? There's no direct relation between the length of a transfer and the maxpacket size of the endpoint. A single transfer can comprise a partial data packet or multiple data packets. Transfer lengths are determined more by the size of the available buffers, the expected transfer rate, the acceptable latency, and so on. 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
