[pulseaudio-discuss] Naming USB card sources with same vendor/product/serial id

[Miguel Paolino]

Hi all,

I have several USB cards, cheap ones, all have the same vendor, product and
serial id. The cards are all assigned different names using udev rules
based on the usb port they are plugged in.

$ cat /proc/asound/cards:

...

 1 [MyCard1     ]: USB-Audio - USB Audio Device
                      GeneralPlus USB Audio Device at
usb-0000:00:1d.0-1.3.5, full speed
 2 [MyCard2     ]: USB-Audio - USB Audio Device
                      GeneralPlus USB Audio Device at
usb-0000:00:1d.0-1.3.7, full speed


The problem I'm having is that I cannot get a reliable config that allows
me to name and use the sources of these cards with libpulseaudio. If I use
module-udev card and source naming depends on the order they are plugged in
like:

alsa_input.usb-GeneralPlus_USB_Audio_Device-00.analog-mono.0
alsa_input.usb-GeneralPlus_USB_Audio_Device-00.analog-mono.2

The closest I could get was configuring the sources statically using
module-alsa-source naming them with the 'name' argument and using
device=hw:MyCard[1,2].
This works but the problem is if I unplug one of the cards and I need to
plug it again and restart pulseaudio because the moment the card is
unplugged pulseaudio unloads the module. The only way to get it working
again is restarting, and if I don't plug the card back pulseaudio refuses
to start because the system is missing a card that's in the config. This of
course have the additional and most important inconvenience of cancelling
any audio capture I might be doing using the other cards.

I tried all sorts of things with udev trying to accomplish this using only
module-udev and I failed miserably.

Is there a way to accomplish what I want?

I'm using:

pulseaudio 9.0
udev 231
kernel 4.8.0

Thanks!
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