fix(pulseaudio,pipewire): build on targets without 64-bit atomics

.github/workflows/platforms.yml

@@ -34,10 +34,10 @@ env:
   MSRV_WASM: "1.85"
   MSRV_WINDOWS: "1.85"
 
-  PACKAGES_LINUX: libasound2-dev libjack-jackd2-dev libdbus-1-dev libpipewire-0.3-dev
+  PACKAGES_LINUX: libasound2-dev libdbus-1-dev libjack-jackd2-dev libpipewire-0.3-dev
 
   # System packages required by the docs.rs feature set and available on docs.rs build environment.
-  PACKAGES_DOCS_RS: libasound2-dev libjack-jackd2-dev libdbus-1-dev
+  PACKAGES_DOCS_RS: libasound2-dev libdbus-1-dev libjack-jackd2-dev
 
   ANDROID_COMPILE_SDK: "30"
   ANDROID_BUILD_TOOLS: "30.0.3"
@@ -180,6 +180,41 @@ jobs:
       - name: Check PipeWire on Debian Bookworm
         run: cargo check --features pipewire --workspace --verbose
 
+  # MIPS (Tier 3 target, requires nightly + build-std; no native 64-bit atomics)
+  mipsel:
+    runs-on: ubuntu-latest
+    container:
+      image: buildpack-deps:bookworm
+    env:
+      TARGET: mipsel-unknown-linux-gnu
+      PKG_CONFIG_ALLOW_CROSS: "1"
+      PKG_CONFIG_PATH: /usr/lib/mipsel-linux-gnu/pkgconfig/
+      CARGO_TARGET_MIPSEL_UNKNOWN_LINUX_GNU_LINKER: mipsel-linux-gnu-gcc
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Install mipsel cross-toolchain and audio libs
+        run: |
+          dpkg --add-architecture mipsel
+          apt-get update -qq
+          apt-get install -y --no-install-recommends libclang-dev crossbuild-essential-mipsel $(for p in ${{ env.PACKAGES_LINUX }}; do echo "$p:mipsel"; done)
+
+      - name: Install Rust nightly (for build-std)
+        uses: dtolnay/rust-toolchain@nightly
+        with:
+          components: rust-src
+
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: mipsel
+
+      - name: Check examples (default features)
+        run: cargo +nightly check --examples --workspace --verbose --target ${{ env.TARGET }} -Z build-std
+
+      - name: Check examples (all features)
+        run: cargo +nightly check --examples --all-features --workspace --verbose --target ${{ env.TARGET }} -Z build-std
+
   # Windows (x86_64 and i686)
   windows:
     strategy:
@@ -577,18 +612,19 @@ jobs:
   publish-cpal:
     if: github.event_name == 'release' && startsWith(github.ref, 'refs/tags/v')
     needs:
+      - android
+      - docs-cpal
+      - ios
       - linux
       - linux-armv7
-      - pipewire-bookworm
-      - windows
       - macos
-      - android
-      - ios
+      - mipsel
+      - pipewire-bookworm
       - tvos
-      - wasm-bindgen
       - wasm-audioworklet
+      - wasm-bindgen
       - wasm-wasip1
-      - docs-cpal
+      - windows
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5

CHANGELOG.md

@@ -34,7 +34,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **JACK**: Channel enumeration is no longer capped at the physical system port count.
 - **PipeWire**: Fix streams starting audio before `play()` is called.
 - **PipeWire**: Streams for a specific device no longer auto-reroute if it disappears.
+- **PipeWire**: Build on 32-bit targets without native 64-bit atomics.
 - **PulseAudio**: `NoData` errors are no longer misreported as buffer xruns.
+- **PulseAudio**: Build on 32-bit targets without native 64-bit atomics.
 - **visionOS**: The CoreAudio backend now builds.
 - **WASAPI**: Default device changes no longer report `DeviceChanged`, which wrongly implied the stream had rerouted automatically.
 - **WASAPI**: Reported buffer sizes are no longer off by one frame.

Cargo.toml

@@ -74,7 +74,7 @@ pipewire = ["dep:pipewire"]
 # Provides audio I/O support on Linux and some BSDs using the PulseAudio sound server
 # Requires: PulseAudio server and client libraries installed on the system
 # Platform: Linux, DragonFly BSD, FreeBSD, NetBSD
-pulseaudio = ["dep:pulseaudio", "dep:futures"]
+pulseaudio = ["dep:pulseaudio", "dep:futures", "dep:portable-atomic"]
 
 # WebAssembly backend using wasm-bindgen
 # Enables the Web Audio API backend for browser-based audio
@@ -91,6 +91,11 @@ wasm-bindgen = [
 [dependencies]
 dasp_sample = "0.11"
 
+# Polyfills 64-bit atomics on targets without native support (e.g. mips, powerpc,
+# riscv32); used by the pulseaudio backend's lock-free latency tracking.
+[target.'cfg(not(target_has_atomic = "64"))'.dependencies]
+portable-atomic = { version = "1", optional = true }
+
 [dev-dependencies]
 anyhow = "1.0"
 hound = "3.5"

src/host/pipewire/device.rs

@@ -4,7 +4,7 @@ use std::{
     hash::{Hash, Hasher},
     rc::Rc,
     sync::{
-        atomic::{AtomicBool, AtomicU64, Ordering},
+        atomic::{AtomicBool, AtomicU32, Ordering},
         mpsc, Arc,
     },
     thread,
@@ -369,10 +369,10 @@ impl DeviceTrait for Device {
         let device = self.clone();
         let wait_timeout = timeout.unwrap_or(Duration::from_secs(2));
         let initial_quantum = match config.buffer_size {
-            BufferSize::Fixed(n) => n as u64,
-            BufferSize::Default => self.quantum as u64,
+            BufferSize::Fixed(n) => n,
+            BufferSize::Default => self.quantum,
         };
-        let last_quantum = Arc::new(AtomicU64::new(initial_quantum));
+        let last_quantum = Arc::new(AtomicU32::new(initial_quantum));
         let last_quantum_clone = last_quantum.clone();
         // Keep `capture` monotonic: pw_time delay() grows when another client joins
         // needing a larger buffer, which can pull `capture` backward.
@@ -547,10 +547,10 @@ impl DeviceTrait for Device {
         let device = self.clone();
         let wait_timeout = timeout.unwrap_or(Duration::from_secs(2));
         let initial_quantum = match config.buffer_size {
-            BufferSize::Fixed(n) => n as u64,
-            BufferSize::Default => self.quantum as u64,
+            BufferSize::Fixed(n) => n,
+            BufferSize::Default => self.quantum,
         };
-        let last_quantum = Arc::new(AtomicU64::new(initial_quantum));
+        let last_quantum = Arc::new(AtomicU32::new(initial_quantum));
         let last_quantum_clone = last_quantum.clone();
         // Keep `playback` monotonic: pw_time delay() shrinks when other clients that needed
         // a larger buffer leave the graph, which can pull `playback` backward.

src/host/pipewire/stream.rs

@@ -2,7 +2,7 @@ use std::{
     cell::RefCell,
     rc::Rc,
     sync::{
-        atomic::{AtomicBool, AtomicU64, Ordering},
+        atomic::{AtomicBool, AtomicU32, Ordering},
         Arc, Mutex,
     },
     thread::JoinHandle,
@@ -81,7 +81,7 @@ pub(super) enum StreamCommand {
 pub struct Stream {
     handle: Option<JoinHandle<()>>,
     controller: pw::channel::Sender<StreamCommand>,
-    last_quantum: Arc<AtomicU64>,
+    last_quantum: Arc<AtomicU32>,
     start: Instant,
     latch: Latch,
 }
@@ -90,7 +90,7 @@ impl Stream {
     pub(super) fn new(
         handle: JoinHandle<()>,
         controller: pw::channel::Sender<StreamCommand>,
-        last_quantum: Arc<AtomicU64>,
+        last_quantum: Arc<AtomicU32>,
         start: Instant,
         latch: Latch,
     ) -> Self {
@@ -224,7 +224,7 @@ pub struct UserData<D> {
     error_callback: ErrorCallbackArc,
     sample_format: SampleFormat,
     format: AudioInfoRaw,
-    last_quantum: Arc<AtomicU64>,
+    last_quantum: Arc<AtomicU32>,
     start: Instant,
     is_default_device: bool,
     has_connected: bool,
@@ -311,14 +311,14 @@ where
     fn publish_data_in(&mut self, stream: &pw::stream::Stream, frames: usize, data: &Data) {
         #[cfg(feature = "realtime")]
         {
-            let prev = self.last_quantum.swap(frames as u64, Ordering::Relaxed);
-            if !self.rt_promoted || frames as u64 != prev {
+            let prev = self.last_quantum.swap(frames as u32, Ordering::Relaxed);
+            if !self.rt_promoted || frames as u32 != prev {
                 self.promote_realtime(frames as FrameCount);
             }
         }
 
         #[cfg(not(feature = "realtime"))]
-        self.last_quantum.store(frames as u64, Ordering::Relaxed);
+        self.last_quantum.store(frames as u32, Ordering::Relaxed);
 
         let (callback, capture) = match pw_stream_time(stream) {
             Some(t) => {
@@ -352,14 +352,14 @@ where
     fn publish_data_out(&mut self, stream: &pw::stream::Stream, frames: usize, data: &mut Data) {
         #[cfg(feature = "realtime")]
         {
-            let prev = self.last_quantum.swap(frames as u64, Ordering::Relaxed);
-            if !self.rt_promoted || frames as u64 != prev {
+            let prev = self.last_quantum.swap(frames as u32, Ordering::Relaxed);
+            if !self.rt_promoted || frames as u32 != prev {
                 self.promote_realtime(frames as FrameCount);
             }
         }
 
         #[cfg(not(feature = "realtime"))]
-        self.last_quantum.store(frames as u64, Ordering::Relaxed);
+        self.last_quantum.store(frames as u32, Ordering::Relaxed);
 
         let (callback, playback) = match pw_stream_time(stream) {
             Some(t) => {
@@ -539,7 +539,7 @@ pub struct ConnectParams {
     pub config: StreamConfig,
     pub properties: PropertiesBox,
     pub sample_format: SampleFormat,
-    pub last_quantum: Arc<AtomicU64>,
+    pub last_quantum: Arc<AtomicU32>,
     pub start: Instant,
     pub connect_automatically: bool,
     pub is_default_device: bool,

src/host/pulseaudio/stream.rs

@@ -1,11 +1,16 @@
 use std::{
     sync::{
-        atomic::{AtomicBool, AtomicU64, Ordering},
+        atomic::{AtomicBool, Ordering},
         Arc, Condvar, Mutex,
     },
     time::{Duration, Instant},
 };
 
+#[cfg(not(target_has_atomic = "64"))]
+use portable_atomic::AtomicU64;
+#[cfg(target_has_atomic = "64")]
+use std::sync::atomic::AtomicU64;
+
 use futures::executor::block_on;
 use futures::FutureExt as _;
 use pulseaudio::{protocol, AsPlaybackSource};