On Sat, May 17, 2014 at 05:41:06PM +0000, Christian Weisgerber wrote: > I just tried to hang a USB audio dongle off my spiffy new machine, > and was rudely reminded of this long-standing issue: > > ehci0: Error opening low/full speed isoc endpoint. > A low/full speed device is attached to a USB2 hub, and transaction > translations are not yet supported. > > Right. I had seen this before but forgotten about it, and the > previous box where I had successfully tested this uaudio device > happened to be my Sun Blade 100, which only has USB1.1 to begin > with. > > So it seems it is currently impossible to run any uaudio(4) device > that only supports USB1 speeds on a machine with USB2 ports. Maybe > there are audio dongles that run at hi-speed, otherwise uaudio(4) > looks pretty useless.
exactly, on modern machines. As long as we lack the necessary support for usb2 hubs (isoc endpoints behind hubs, more precisely). certain usb hosts don't use hubs or can work as uhci (by disabling echi), in which case uaudio works. Others use rate matching hubs, on which uaudio can't work yet. -- Alexandre
