Re: [Alsa-user] a mono phone interface

[Alfred G. <alf...@ag...>]

Ladies and Gentlemen,

A few month ago I wrote about my problem with a rather old USB phone 
device. The device works fine on my older systems but fails on my 
relatively new desktop. I am doing my tests with aplay like this:
    aplay -v -D usb-phone -t wav /usr/share/sounds/alsa/Front_Center.wav
with the attached /etc/asound.conf file.

I am using CentOS systems, by now version 8 (version 7 and some earlier
in qemu-kvm VM's), but the original use of the phone device is on a real
centos-6 system. I originally assumed my problem was caused by the newer
version of the software or by the change from i686 to x86_64 hardware. 
However, I now know that the device works just fine under Centos-8 and 
on x86_64 hardware. The problem arises in the USB hardware and the USB
drivers for it. On the systems where the device works as expected the
hardware driver used is uhci_hcd (which I think is actually an ehci_hcd 
companion), on the system where the phone device doesn't work the USB
driver is xhci_hcd. On the system with xhci_hcd driver there are no other 
drivers available (I have not made any experiments at the UEFI level).
In a VM which provides a uhci_hcd driver on the host with the xhci_hcd 
driver the test also fails.

The centos kernel's are always relatively "old", the current centos-8
version is 4.18.0-147.5.1.el8_1. I now assume that the problem lies
somewhere between the snd-usb-audio module and the uhci_hcd emulation 
of the xhci_hcd driver. So my question now is, what can be done to make 
my old, slow USB phone device work with the xhci_hcd driver?

I will gladly provide more details but would need to know what could
help in this case.

Any advice would be appreciated. Thanks, AG

-- 
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   Alfred Ganz					alfred-ganz:at:agci.com
   AG Consulting				(203) 624-9667
   440 Prospect Street # 11
   New Haven, CT 06511
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