On Fri, 30 Sep 2011, gene heskett wrote: > In the lsusb, bus 2 is said to be a linux 1.1, so I assume everything on it > is running in 12mbit mode. Or 1.5 Mb/s. Yes. > I just moved the LX710 keyboard to a different > plug on the back panel, but it still shows up as one of the 4 devices on > the slow bus. > > I'm assuming that a given hub cannot be accessed by both ehci and ohci > drivers, which means I should put all the slow stuff on a separate hub, no? Put all the slow stuff except for the webcam on a separate hub, and make sure it is a USB-2.0 hub plugged directly into the computer. Leave the webcam attached to the OHCI controller. Since the webcam needs to use almost all of the controller's bandwidth, you don't want to have any other devices on the same bus. > I may have another port powered slow hub but I'm assuming its too old to > translate between full speed and 1.1 and I just tried it, its a usb1.1 > device all the way. Low speed = 1.5 Mb/s. Full speed = 12 Mb/s. High speed = 480 Mb/s. USB-1.1 supports only low and full speeds. USB-2.0 supports all three speeds, and all USB-2.0 hubs are required to do the necessary speed conversions. (And in case you're interested, SuperSpeed = 5000 Mb/s and USB-3.0 supports all four speeds.) > All of this leads to a pair of questions. > > 1, can a recently purchased accessory hub do speed translations? The purchase date isn't what matters -- you can still buy USB-1.1 hubs. What matters is the USB version supported by the hub. Every USB-2.0 hub can do speed translations. > 2, would it do me any good to put the known slow stuff on such a hub so > that all the motherboard ports (6) can then be claimed by ehci_hid? That's not how it works. When a USB device is plugged into the computer, if the device is capable of running at high speed then it will be claimed by the EHCI controller. Otherwise it will be claimed by the OHCI controller. On the other hand, a full-speed device plugged into a high-speed hub which is plugged into the computer will be claimed by the EHCI controller, because that controller already owns the hub and therefore it has to own all devices below that hub. Conversely, a high-speed-capable device plugged into a USB-1.1 hub which is plugged into the computer will be claimed by the OHCI controller, because that controller already owns the hub. > I know the wireless keyboard and mouse are low. And that scanner might be > too, its quite long in the tooth. And that LX710 keyboard receiver when > plugged into that old front panel breakout hub, it is not found early > enough to control the bios. That could be a pita, forcing me to plug in a > ps2 keyboard. They seem to be getting rare in these here parts. > > From the lsusb -v, is that camera even able to do usb-2.0? If its a 1.1 > only, then I may as well bin it and go look for a better one. The lsusb output shows that the camera's bcdUSB is 1.10. That indicates it supports USB-1.1 and therefore isn't capable of running at high speed. Was the camera plugged directly into the computer? If it was, you can be certain it doesn't support high speed -- if it did, it would be claimed by the EHCI controller. On the other hand, any device plugged into a full-speed hub will be forced to run at full speed (since the hub doesn't support anything faster), even if the device is capable of high speed. 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
