On Sat, 28 Aug 2010, Artem Makhutov wrote: > Hi, > > On Sat, 28 Aug 2010, Artem Makhutov wrote: > > > >> It is much harder to reproduce the problem when no hubs are in use. > >> What is the big deal in not using hubs? > >> > > There are several reasons. First, not having the extra hardware > > removes a whole class of possible causes of errors. > The problem is much easier to reproduce by using hubs. Which would seem to indicate a hardware component is involved somehow. There's no software difference between a device plugged into a hub and a directly-attached device. > > Second, not having > > the hubs makes the logs easier to follow since they won't contain a lot > > of uninteresting extra entries. > Ok. > > Third, without the hubs you won't be able to connect as many modems, > > which again makes the logs easier to follow. > Thats not true :) I can connect the same amount of modems without hubs :) Yes, that's what I saw when I looked at your error log! A bunch of modems were connected to your motherboard's EHCI controller and several others were running at full speed on your add-on UHCI controllers. The problem occurred only with one of the modems running at high speed. I would expect that unplugging those attached to the add-on card wouldn't make any difference at all. > Unfortunately the problem can only be triggered by connecting a lot of > modems. That's another indication of a hardware problem. Furthermore, this particular error code (xacterr in the log) comes directly from the controller itself. It indicates that the computer failed to receive a packet the modem should have sent. Note that in the error log, all the errors occurred for the device plugged into port 1 -- the modem providing ttyUSB0, ttyUSB1, and ttyUSB2. Maybe that particular port or that particular modem has a bad cable connection. (And don't overlook the possibility of a bad cable inside the computer case, connecting the motherboard to the USB port.) > > Fourth, without the high-speed hubs the modems will have to > > connect to a full-speed USB-1.1 controller instead of a high-speed > > USB-2.0 controller, removing yet another possible source of errors and > > complexity. > > > How do you know that they will connect to USB-1.1 instead of USB-2.0? > I was believing that the modems are USB-2.0 devices? > How can I find out if they are USB-1.1 or 2.0? I was wrong. They are indeed all USB-2.0 devices and they all run at high speed if connected to a high-speed controller. As for FreeBSD... How can you be sure that these errors don't occur under that OS? Maybe they are simply being ignored instead of reported by the driver and in the log. 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
