Dakota Linux Audio Stack#

Dakota's audio stack is built from three cooperating layers: PipeWire (the audio/video server), WirePlumber (the session/policy manager), and ALSA (hardware mixer state). Each is shipped as a dedicated BuildStream element and composed into the image via elements/bluefin/deps.bst.

PipeWire#

Dakota pins PipeWire to 1.6.8, applied as a patch on top of the upstream freedesktop-sdk base element 1.

The patch targets elements/components/pipewire-base.bst 2 and does two things:

1. Advances the source ref from 1.4.9 to 1.6.8 (ref: 1.6.8-0-gb741e0c74f5436f0c925f7741140db0efd32cf4e) 3
2. Disables several optional build dependencies to reduce image size and avoid pulling in heavy codec libraries: fftw, bluez5-codec-ldac-dec, bluez5-plc-spandsp, and onnxruntime 4

No repository-local PipeWire configuration files exist — PipeWire's default runtime config is used as-is. Session policy is delegated entirely to WirePlumber.

WirePlumber — PC-Speaker Suppression#

The only Dakota-specific WirePlumber customization is files/wireplumber/51-disable-pcsp.conf, which adds an ALSA monitor rule to set device.disabled = true for the alsa_card.platform-pcspkr device 5.

Why it exists: Without this rule, the snd_pcsp kernel driver exposes the PC speaker as a PCM sink. After a suspend/resume cycle WirePlumber can select it as the fallback default sink, silencing all desktop audio (dakota#1248). The rule keeps the driver loaded (console beeps still work) while hiding the card from the audio device list 6.

The config is packaged by elements/bluefin/wireplumber-pcsp.bst, which installs it to:

%{datadir}/wireplumber/wireplumber.conf.d/51-disable-pcsp.conf

7

This element is pulled into every image build through deps.bst.

ALSA Utilities — Mixer State Persistence#

freedesktop-sdk ships alsa-lib but omits alsa-utils, which means there is no alsactl, no alsa-restore/alsa-state systemd units, and no udev restore rule. On hardware where power-on mixer defaults are muted or misrouted, this surfaces as "boots with broken sound" (dakota#1027) 8.

elements/bluefin/alsa-utils.bst builds alsa-utils 1.2.14 and trims it to only the mixer-state machinery 9:

Lockstep constraint: alsa-utils and alsa-lib must be the same version. alsa-utils is pinned to 1.2.14 to match freedesktop-sdk's alsa-lib. Never bump them independently 10.

Component Map#

For PipeWire upstream documentation see docs.pipewire.org. For WirePlumber policy configuration refer to the WirePlumber docs.