On Friday, September 30, 2011 07:05:29 PM Alan Stern did opine: > 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. It looks as if there will be 3 devices, the wireless keyboard & mouse, this poor camera, and a 5 YO belkin ups that seems to be stuck in 1997. > 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. Great. > (And in case you're interested, SuperSpeed = 5000 Mb/s and USB-3.0 > supports all four speeds.) So one s/b careful what one buys when next shopping for a motherboard. But I am not shopping just yet, waiting for the USB-3.0 teething pains to subside a bit. > > 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. That will help considerably I'd think. > > 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. Gotcha. Thanks. > > 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. So its guilty as charged yur honor. ;-) > 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. It was and is, plugged into a rear port, or a breakout port, also plugged into the motherboard. No intervening hubs. If that is the case, I'll get another 2.0 hub, _and_ a faster camera. > 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. That I had grokked. > Alan Stern Thanks Alan, we'll close out this chapter & verse then. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The best prophet of the future is the past. -- 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
