PulseAudio doesn't detect USB hot-plugging if no USB device was connected at startup

[tmigone]

To replicate

1. Start audio block
2. Connect a USB sound card to your device

Running udev monitor or aplay -l will show that both udev and ALSA are picking up the sound card. However running pactl list sinks will yield no result. PulseAudio is ignoring the udev events it seems.

If you invert the order of operations however hotplugging works as intended:

1. Connect a USB sound card to your device
2. Start audio block

This might be related to how systemd ALSA rules are handled, and how PulseAudio interacts with that (seems a bit sketchy?). Some references here for further investigation:

• https://github.com/pulseaudio/pulseaudio/blob/master/src/modules/module-udev-detect.c#L476-L482
• https://cgit.freedesktop.org/systemd/systemd/tree/rules/78-sound-card.rules?id=1d09582ab9d8bc619de3a01f01d614eab44d31c0#n8

[jellyfish-bot]

[tmigone] This issue has attached support thread https://jel.ly.fish/23fd0d70-7d8e-446e-a4d5-891f1f705c80

[i-garrison]

I'd guess this could be kernel or alsa-lib issue so please re-test. The error reported looks almost like if kernel alsa layer created /dev/snd/ entry (which is getting picked by pulseaudio udev monitoring routine) before kernel alsa driver completed all things required for alsa-lib to actually use the device successfully - this should never happen.

[bbugh]

I know this has been ages, but was any progress made on this? That jellyfish URL seems to be invalid.

We're having issues with a container starting up and even when the USB device is plugged in, it doesn't always recognize it in time. Even when it does, no hot swapping seems to work. When this occurs, after boot, there's no sound card discovered and no way to fix it without restarting the service, which starts the process over and may still not fix it.