ASIO: open control panel

CHANGELOG.md

@@ -87,6 +87,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **ALSA**: `Debug` implementations for `Host`, `Device`, `Stream`, and internal types.
 - **ALSA**: Example demonstrating ALSA error suppression during enumeration.
 - **ALSA**: Support for native DSD playback.
+- **ASIO**: Extension trait for ASIO devices, which allows opening the control panel.
 - **WASAPI**: Enable as-necessary resampling in the WASAPI server process.
 
 ### Changed

asio-sys/build.rs

@@ -239,6 +239,7 @@ fn create_bindings(cpal_asio_dir: &PathBuf) {
         .allowlist_function("ASIOStart")
         .allowlist_function("ASIOStop")
         .allowlist_function("ASIODisposeBuffers")
+        .allowlist_function("ASIOControlPanel")
         .allowlist_function("ASIOExit")
         .allowlist_function("load_asio_driver")
         .allowlist_function("remove_current_driver")

asio-sys/src/bindings/mod.rs

@@ -924,6 +924,11 @@ impl Driver {
         let mut dcb = DRIVER_EVENT_CALLBACKS.lock().unwrap();
         dcb.retain(|&(id, _)| id != rem_id);
     }
+
+    /// Opens the ASIO driver's control panel window.
+    pub fn open_control_panel(&self) -> Result<(), AsioError> {
+        unsafe { asio_result!(ai::ASIOControlPanel()) }
+    }
 }
 
 impl DriverState {

src/host/asio/mod.rs

@@ -26,7 +26,7 @@ mod stream;
 ///
 /// ASIO only supports loading a single driver at a time globally, so all Host instances
 /// must share the same underlying sys::Asio wrapper to properly coordinate driver access.
-static GLOBAL_ASIO: OnceLock<Arc<sys::Asio>> = OnceLock::new();
+pub(crate) static GLOBAL_ASIO: OnceLock<Arc<sys::Asio>> = OnceLock::new();
 
 /// The host for ASIO.
 #[derive(Debug)]

src/platform/asio.rs

@@ -0,0 +1,72 @@
+//! Implementations for ASIO-specific device functionality.
+
+#[allow(unused_imports)]
+use crate::BackendSpecificError;
+use crate::Device;
+#[allow(unused_imports)]
+use std::marker::PhantomData;
+
+/// Extension trait to get the ASIO device.
+pub trait AsioDeviceExt {
+    /// Returns the [AsioDevice] interface if this is an ASIO device.
+    fn as_asio(&self) -> Option<AsioDevice<'_>>;
+}
+
+/// A wrapper providing access to ASIO-specific device functionality.
+#[derive(Clone)]
+pub struct AsioDevice<'a> {
+    #[cfg(all(target_os = "windows", feature = "asio"))]
+    inner: &'a crate::host::asio::Device,
+
+    // Dummy marker for lifetime 'a.
+    #[cfg(not(all(target_os = "windows", feature = "asio")))]
+    _marker: PhantomData<&'a ()>,
+}
+
+impl AsioDevice<'_> {
+    /// Opens the ASIO driver's control panel window.
+    ///
+    /// This provides access to device-specific settings like buffer size,
+    /// sample rate, input/output routing, and hardware-specific features.
+    ///
+    /// # Blocking Behavior
+    ///
+    /// This call may block until the user closes the control panel.
+    /// Consider spawning a thread to avoid blocking the main thread.
+    pub fn open_control_panel(&self) -> Result<(), BackendSpecificError> {
+        #[cfg(all(target_os = "windows", feature = "asio"))]
+        {
+            use crate::host::asio::GLOBAL_ASIO;
+
+            let description = self.inner.description().map_err(|e| BackendSpecificError {
+                description: format!("{e:?}"),
+            })?;
+            let driver_name = description.name();
+
+            GLOBAL_ASIO
+                .get()
+                .expect("GLOBAL_ASIO is always set when an ASIO device exists")
+                .load_driver(driver_name)
+                .map_err(|e| BackendSpecificError {
+                    description: format!("{e:?}"),
+                })?
+                .open_control_panel()
+                .map_err(|e| BackendSpecificError {
+                    description: format!("{e:?}"),
+                })
+        }
+
+        #[cfg(not(all(target_os = "windows", feature = "asio")))]
+        unreachable!("AsioDevice cannot be constructed on non-ASIO platforms")
+    }
+}
+
+impl AsioDeviceExt for Device {
+    fn as_asio(&self) -> Option<AsioDevice<'_>> {
+        match self.as_inner() {
+            #[cfg(all(target_os = "windows", feature = "asio"))]
+            crate::platform::DeviceInner::Asio(d) => Some(AsioDevice { inner: d }),
+            _ => None,
+        }
+    }
+}

src/platform/mod.rs

@@ -10,6 +10,8 @@ pub use self::platform_impl::*;
 #[cfg(feature = "custom")]
 pub use crate::host::custom::{Device as CustomDevice, Host as CustomHost, Stream as CustomStream};
 
+pub mod asio;
+
 /// A macro to assist with implementing a platform's dynamically dispatched [`Host`] type.
 ///
 /// These dynamically dispatched types are necessary to allow for users to switch between hosts at