Udev and Pulse
This is about using a USB DAC (digital-analog audio converter) in Sailfish OS. It is an external device that records analog signals via USB, often used in music production and art.
You need to become root:
# devel-su
#echo 'ATTRS{id}=="mtsndcard", ENV{PULSE_IGNORE}="1"' > /etc/udev/rules.d/89-pulseaudio-usb.rules
cd /etc/pulse/xpolicy.conf.d
mv usbaudio.conf.disabled usbaudio.conf
pactl load-module module-udev-detect
The last command can be persisted with a systemd unit THIS IS NOT finished.
viedit /etc/home/defaultuser/.config/systemd/system/user/pulse_udev.service
[Unit]
Description=udev pactl to start usb udev-pactl-start-usb-dac
[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/usr/bin/pactl load-module module-udev-detect
[Install]
WantedBy=multi-user.target
Then run
systemctl --user enable pulse_udev.service
Article discussion: USB DAC playback on Sailfish OS Forum