why I cannot use C-Media USB Sound device when it's plugged on hub together with other devices?
- From: 张韡武 <zhangweiwu@xxxxxxxxxx>
- Date: Sat, 28 Oct 2006 03:03:01 +0800
Hello. I got a C-Media USB Headphone Set (a small USB Sound device).
1: if it's plugged directly on the USB port on motherboard (Intel
Corporation 82801EB/ER, UHCI+EHCI), it works. In /proc/bus/usb/devices it
shows this device is connected to UHCI Controller.
2: if it's plugged directly on the USB port on PCI-usb card (NEC
Corporation USB, OHCI+EHCI), it works. In /proc/bus/usb/devices it shows
this device is connected to OHCI Controller.
3: if it's plugged on a USB 2.0 Hub, and it's the only device plugged on
this hub, it works. Interestingly, if the hub is plugged to the USB port
on the monther board (Intel UHCI+EHCI), the hub is shown in
/proc/bus/usb/devices connected to a UHCI controller; if the hub is
plugged to the USB port on the PCI USB card (NEC OHCI+EHCI), the hub is
shown in /proc/bus/usb/devices connected to a OHCI controller;
4: if it's plugged on a USB 2.0 hub which already have other devices
plugged on (typically, a USB Mouse), it will NOT WORK. Any application
uses sound, be it ALSA or OSS app, simply hangs when it wish to play
sound. Interestingly, the hub is shown in /proc/bus/usb/devices connected
to a EHCI port, and the USB Sound device in turn connect to the hub.
It looks like if the sound card is connected to an EHCI controller, it
will not work.
I am pretty interested in this problem: if I wish to use this USB Sound
device on a hub which already have other USB devices plugged in, is it
possible? what should I do?
.
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