Hello and thanks for the explanations, Alan! On Sun, 6 Mar 2005, Alan Stern wrote:
> Only for directly connected devices. What matters is the speed at which > the computer transmits. When the computer is connected to a USB-2.0 hub > it will always talk to the hub at high speed, even if there are full- or > low-speed devices plugged into the hub. (The hub translates the messages > into corresponding lower-speed packets.) Conversely, when a full- or > low-speed device is connected directly to the computer, transmission > takes place at full or low speed -- otherwise the device wouldn't work -- > using the companion controller. Ok, that's exactly the piece of information I was missing. > The problem occurs when a full- or low-speed device plugged into a USB-2.0 > hub running at high speed needs to use isochronous transfers. The > isochronous translations aren't yet supported very well. Ok. Not a big problem for me - I can certainly plug in the Bluetooth dongle directly into a free 1.1 / 2.0 port - I still have a couple free. Just that I'll have to plunge under the desk each time:-) > > I think, I did have this configuration before - 2.0 hub with mixed 2.0 and > > 1.1 devices, but that was a VIA uhci / ehci controller, around 2.6.8 > > perhaps? And it did work. > > It depends on the type of transfers. Only isochronous transfers will > cause a problem. And of course, that's what a Bluetooth adapter uses... > > > Anyway, under 2.6.11, it works, although I still got on Bluetooth plug-in: > > > > usb 1-6.4: new full speed USB device using ehci_hcd and address 4 > > usb 1-6.4: device descriptor read/64, error -32 > > usb 1-6.4: device descriptor read/64, error -32 > > usb 1-6.4: new full speed USB device using ehci_hcd and address 5 > > Bluetooth: HCI USB driver ver 2.8 > > usbcore: registered new driver hci_usb > > hci_usb_isoc_rx_submit: hci0 isoc rx submit failed urb da8b5214 err -12 > > hci_usb_isoc_rx_submit: hci0 isoc rx submit failed urb da8b5214 err -12 > > You can see it right there: the "isoc" submission failed. > > > But then it seems to work. > > I guess the driver falls back to a mode that doesn't use isochronous > transfers. However I don't know much about Bluetooth USB adapters. Hmm... It is a pity one cannot see per endpoint activity statistics? > > > And the card-reader works too! > > Card readers don't use isochronous transfers. Yep, but last time I checked it it didn't work that way (on the hub with ehci) under 2.6.10. Thanks Guennadi --- Guennadi Liakhovetski ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
