Hi Devin, On Monday 28 September 2009 21:13:52 Devin Heitmueller wrote: > Hello, > > I have been doing some testing in an attempt to support two USB video > capture devices on the same bus. > > For a single device running with maxpacket of 3072 per microframe, the > EHCI driver is indicating 57% utilization of the bus (the sysfs stats > already takes into account the fact that only 80% of the bus is > available for isoc traffic). 3072 bytes * 8000 microframes/s * 8 bit/byte / 80% / 480e6 = 51.2% You also have to take the USB overhead into account, so the actual value will be a bit larger than that. 57% seems plausible. > Is this expected behavior? By my math, an alternate of 3072 should > take exactly 50% of the available bandwidth. Have I misinterpreted > the spec? > > I'm willing to spend some cycles to dig into echi_sched.c if somebody > can offer some insight as to whether this is expected behavior. I > just want to avoid taking the time to debug this, only to find out > that it is behaving according to spec. -- Regards, Laurent Pinchart -- 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
