Trying to get isochronous transfers for uaudio device to work with EHCI on NSLU2 USB port

[Donald T Hayford <don%donhayford.com@localhost>]

Not sure which is the correct forum for this, so I'll start with users 
and port-arm (though I don't really think this is a port-arm problem).  
If I'm in the wrong spot, please let me know.

The long and short of it is I'm trying to get USB audio to work through 
a USB hub on the NSLU2 (arm-xscale) device.  If I put the USB audio 
device into one of the two USB ports built into the NSLU2, everything 
works fine.  The messages to the system console are:

> ehci0: handing over full speed device on port 2 to ohci0
> uaudio0 at uhub0 port 1 configuration 1 interface 0: C-Media INC. USB 
Audio, rev 1.10/0.10, addr 2
> uaudio0: audio rev 1.00
> audio0 at uaudio0: full duplex, independent
and the device works ok.

If I unplug the USB device and plug it into a hub, I get:

> uaudio0 at uhub3 port 4 configuration 1 interface 0: C-Media INC. USB 
Audio, rev 1.10/0.10, addr 5
> uaudio0: audio rev 1.00
> audio0 at uaudio0: full duplex, independent
And when I try to use it, I get...
> ehci0: *** Error: opening low/full speed isoc device on ehci, this 
does not work yet. Feel free to implement
> output: write: Input/output error

I thought that ehci isochronous support was added recently by the summer 
of code work.  Do I need to do more than include uaudio in the kernel 
configuration file?  Incidentally, the build instructions for adding 
audio to the NSLU2 are here:  
http://wiki.netbsd.se/How_to_add_USB_audio_to_the_NSLU2

Thanks for your help,
Don Hayford