Implement try-init feature

esp-hal/Cargo.toml

@@ -42,6 +42,7 @@ esp-synopsys-usb-otg     = { version = "0.4.2", optional = true, features = ["fs
 fugit                    = "0.3.7"
 log                      = { version = "0.4.22", optional = true }
 nb                       = "1.1.0"
+once_cell                = { version = "1.20.2", optional = true, default-features = false, features = ["race"] }
 paste                    = "1.0.15"
 portable-atomic          = { version = "1.9.0", default-features = false }
 procmacros               = { version = "0.15.0", package = "esp-hal-procmacros", path = "../esp-hal-procmacros" }
@@ -152,6 +153,9 @@ octal-psram = []
 # This feature is intended for testing; you probably don't want to enable it:
 ci = ["defmt", "bluetooth"]
 
+# Enable `try_init` -- requires once_cell
+try-init = ["once_cell"]
+
 [lints.clippy]
 mixed_attributes_style = "allow"
 

esp-hal/src/lib.rs

@@ -559,3 +559,18 @@ pub fn init(config: Config) -> Peripherals {
 
     peripherals
 }
+
+/// Attempts to initialize the system.
+///
+/// If [`init`] has already been executed, returns [`None`].
+/// (This check is [thread-safe](once_cell::race::OnceBool))
+///
+/// Otherwise, initializes and returns the [`Peripherals`].
+#[cfg(feature = "try-init")]
+pub fn try_init(config: Config) -> Option<Peripherals> {
+    if !Peripherals::initialized() {
+        Some(init(config))
+    } else {
+        None
+    }
+}

esp-hal/src/peripheral.rs

@@ -257,6 +257,8 @@ mod peripheral_macros {
                 ),* $(,)?
             ]
         ) => {
+            #[cfg(feature = "try-init")]
+            use once_cell::race::OnceBool;
 
             /// Contains the generated peripherals which implement [`Peripheral`]
             mod peripherals {
@@ -293,8 +295,25 @@ mod peripheral_macros {
                 }
 
                 impl Peripherals {
+                    #[cfg(feature = "try-init")]
+                    const INITIALIZED: OnceBool = OnceBool::new();
+
+                    #[cfg(feature = "try-init")]
+                    pub(crate) fn initialized() -> bool {
+                        Self::INITIALIZED.get().is_some()
+                    }
+
                     /// Returns all the peripherals *once*
                     #[inline]
+                    #[cfg(feature = "try-init")]
+                    pub(crate) fn take() -> Self {
+                        if let Ok(_) = Self::INITIALIZED.set(true) {
+                            unsafe { Self::steal() }
+                        } else {
+                            panic!("init called more than once!")
+                        }
+                    }
+                    #[cfg(not(feature = "try-init"))]
                     pub(crate) fn take() -> Self {
                         #[no_mangle]
                         static mut _ESP_HAL_DEVICE_PERIPHERALS: bool = false;