On Fri, Apr 15, 2011 at 3:17 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Fri, 15 Apr 2011, Richard Ash wrote: > >> Once it's got going, the usbmon trace looks like this: >> >> f5146880 554152969 C Bi:4:002:1 0 128 = e6232508 0020e72e 3afcf03a >> 03933424 250800b0 e72e3afc f03a030e 83242508 >> f5146880 554152997 S Bi:4:002:1 -115 128 < >> f5146500 554153005 C Bi:4:002:1 0 128 = 260800f0 e72e3afc f03a0326 >> cf4e2608 00d0e72e 3afcf03a 03a21d4f 260800e0 > > ... > >> This is where I get confused - my device is apparently being asked for >> 128 bytes of data, and replying with 128 bytes, but only 32 bytes end >> up in the output. This is for a 64 byte endpoint ... >> >> The last two replies (with reported lengths of 19 and 23 bytes) do >> have 19 and 23 bytes of output data respectively. >> >> 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? Richard -- 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
