[LAD] jackd and usb hub

Clemens Ladisch clemens at ladisch.de
Fri Oct 15 06:44:04 UTC 2010

Luis Garrido wrote:
> So now I am throwing a powered USB hub in. As long as I keep it to
> ALSA usage there is no problem: I can record and playback with, for
> instance, Audacity using the ALSA backend. But anytime I try to launch
> jackd the daemon fails and I get this in /var/log/messages:
> kernel: ALSA sound/usb/usbaudio.c:882: cannot submit datapipe for urb 0, error -28: not enough bandwidth

The code in the EHCI driver that schedules full-speed audio packets is
buggy, so using two audio streams at the same time often does not work.
EHCI is used for all high-speed (USB 2.0) controllers, so to work around
this, you could connect the device directly to the computer (without a
hub) so that the full-speed (USB 1.x) UHCI/OHCI controller driver is
used, or unload the ehci_hcd module so that the hub is forced to run at
USB 1.x speed.  (The rate-matching hub in the Intel P/Q/H 55/57 chipsets
makes both workarounds impossible.)


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