audio: improve backend recovery and add loopback validation

Runner/config/pkg_command_map.conf

@@ -450,6 +450,17 @@ debian:package-set:audio-base=alsa-utils pipewire-bin wireplumber pulseaudio-uti
 ubuntu:package-set:audio-base=alsa-utils
 ubuntu:package-set:audio-desktop=pipewire pipewire-pulse wireplumber pipewire-bin pulseaudio-utils
 
+# Complete playback and recording clients for a selected backend.
+debian:package-set:audio-client-pipewire=pipewire-bin wireplumber
+ubuntu:package-set:audio-client-pipewire=pipewire-bin wireplumber
+centos:package-set:audio-client-pipewire=pipewire-utils wireplumber
+debian:package-set:audio-client-alsa=alsa-utils
+ubuntu:package-set:audio-client-alsa=alsa-utils
+centos:package-set:audio-client-alsa=alsa-utils
+debian:package-set:audio-client-pulseaudio=pulseaudio-utils
+ubuntu:package-set:audio-client-pulseaudio=pulseaudio-utils
+centos:package-set:audio-client-pulseaudio=pulseaudio-utils
+
 # Debian Qualcomm AudioReach overlay stack.
 #
 # This package set is complete by itself because overlay mode checks only
@@ -473,6 +484,14 @@ apt:parecord=pulseaudio-utils
 rpm:pw-play=pipewire-utils
 rpm:pw-record=pipewire-utils
 rpm:pw-cat=pipewire-utils
+rpm:wpctl=wireplumber
+rpm:aplay=alsa-utils
+rpm:arecord=alsa-utils
+rpm:amixer=alsa-utils
+rpm:alsaucm=alsa-utils
+rpm:pactl=pulseaudio-utils
+rpm:paplay=pulseaudio-utils
+rpm:parecord=pulseaudio-utils
 
 # ---------------------------------------------------------------------------
 # Qualcomm Sensors runtime and test packages.

Runner/suites/Multimedia/Audio/AudioLoopback/AudioLoopback.yaml

@@ -0,0 +1,21 @@
+metadata:
+  name: audio-loopback
+  format: "Lava-Test Test Definition 1.0"
+  description: "ALSA playback-to-capture loopback validation"
+  os:
+    - linux
+  scope:
+    - functional
+
+params:
+  DURATION: 5
+  PLAYBACK_DEVICE: ""
+  CAPTURE_DEVICE: ""
+  DMESG_SCAN: 1
+
+run:
+  steps:
+    - REPO_PATH=$PWD
+    - cd Runner/suites/Multimedia/Audio/AudioLoopback/
+    - ./run.sh --duration "${DURATION}" --playback-device "${PLAYBACK_DEVICE}" --capture-device "${CAPTURE_DEVICE}" --dmesg-scan "${DMESG_SCAN}" || true
+    - $REPO_PATH/Runner/utils/send-to-lava.sh AudioLoopback.res

Runner/suites/Multimedia/Audio/AudioLoopback/README.md

@@ -0,0 +1,68 @@
+# AudioLoopback
+
+`AudioLoopback` validates simultaneous playback and capture without downloading
+media. It generates a deterministic 48 kHz, unsigned 8-bit stereo WAV, starts
+capture, plays the reference, and validates the resulting WAV.
+
+Automatic selection uses an active PipeWire or PulseAudio session and its
+physical speaker and microphone routes. PipeWire requires `wpctl`, `pw-record`,
+and `pw-play` or `pw-cat`. PulseAudio requires `pactl`, `parecord`, and `paplay`.
+If no managed backend is usable, the suite falls back to image-provided `aplay`
+and `arecord`. The suite never installs runtime packages.
+
+On Debian and CentOS, a root invocation prepares the regular desktop audio user
+and re-launches the complete test as that user. Automatic selection also
+prepares the user's systemd session so PipeWire and PulseAudio control and data
+paths match the working desktop route. Yocto and Ubuntu keep their existing
+execution behavior.
+
+## Fixture requirement
+
+The selected output must reach the selected input through an acoustic or
+electrical fixture. Automatic selection prefers the active managed backend and
+its physical speaker and microphone endpoints. Supplying either device option
+selects direct ALSA mode, where the unspecified side is discovered. Explicit
+ALSA devices are recommended for fixtures that require fixed PCM endpoints:
+
+```sh
+./run.sh \
+    --playback-device plughw:0,0 \
+    --capture-device plughw:0,1 \
+    --duration 5
+```
+
+When no backend or device inventory exists, the suite reports SKIP with the
+missing prerequisite. When a managed backend is active but its physical routes
+are unusable and direct ALSA fallback also fails, the suite reports FAIL so the
+image or routing regression remains visible. An all-zero capture reports FAIL.
+The default policy does not claim waveform correlation when the input contains
+some other non-zero signal, so retained metrics and the fixture setup remain
+important evidence.
+
+## Result policy
+
+CI-blocking validation is intentionally limited to execution failure and basic
+WAV integrity: corrupt or empty files, header-only payloads, all-zero audio, and
+materially short captures fail. RMS, peak, clipping, digital-silence runs, DC
+offset, large sample transitions, and silent-channel counts are emitted in
+`AUDIO_VALIDATION` records as diagnostic metrics. They do not fail the default
+policy.
+
+## Options
+
+- `--duration SECONDS` selects 2 to 30 seconds.
+- `--playback-device DEVICE` overrides playback discovery.
+- `--capture-device DEVICE` overrides capture discovery and probes a supported
+  format on that exact device.
+- `--dmesg-scan 0|1` controls retained kernel-log evidence.
+- `--no-dmesg` disables the kernel-log scan.
+
+Artifacts are retained below `results/AudioLoopback/run-<timestamp>-<pid>/`.
+
+## Yocto CI
+
+`AudioLoopback.yaml` runs the default five-second test using automatic backend
+and endpoint discovery. A CI device still needs an acoustic or electrical path
+from the selected playback endpoint to the selected capture endpoint. Set
+`PLAYBACK_DEVICE` and `CAPTURE_DEVICE` in the job parameters when direct ALSA
+selection is required by the fixture.