To semi-answer my own question, I was able to make progress by doing a

modprobe -r ehci-hcd

I now get 4 channels in.  It seems like it's not an ALSA or audio problem at all but rather a bug using USB 1.1 devices with ehci-hcd.

Thanks,
Jim

On 3/24/07, Jim Steed <jsteed@gedae.com> wrote:
I am trying to use an MAudio Quattro with Fedora Core 5 PPC build
2.6.16.  I followed the directions here:

http://wiki.linuxquestions.org/wiki/M-Audio_Quattro

but when trying to actually use the Quattro with either jackd or
arecord, I get a dmesg error

cannot submit datapipe for urb 0, err = -28

I get the same error whether I ask for 4 channels or 2.  The error -28
is usb bandwidth, but CONFIG_USB_BANDWIDTH was not set, so I'm not
sure what would be causing it to fail.  What is going wrong?

Thanks,
Jim Steed