Thanks Greg. It is a powered USB hub. The supplies have 2.5 amps to spread across three cameras. One of the hub's ports uses laptop power, but I'm not using that port. The USB 3.0 spec (according to wikipedia) requires that each port be capable of delivering 900 mA, so those power supplies seem a bit low (needs 200mA more). But I strongly doubt the cameras are pulling 900mA since they also work with USB 2.0 ports which specifies a much smaller current. I can measure it if I play with a soldering iron, but I'd rather not risk damaging a camera. I'm still trying to isolate the bad behavior to a single cause. I can still get good captures, albeit randomly after many crashes and segfaults of gstreamer. On 05/16/16 14:20, Greg KH wrote: > On Mon, May 16, 2016 at 02:09:03PM -0700, Brian T. McKee wrote: >> I just noticed that timing matters. If I bring the USB devices up one at >> a time, with lots of time between power ups, things seem to initialize >> better. And there are two ports that won't work much at all and two that >> work until this failure occurs. > Sounds like a power-draw issue, have you checked to ensure that you > aren't just pulling too much power? > > If you use a powered hub, all is good, right? I'd strongly just > recommend doing that. > > good luck! > > greg k-h -- 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
