From 6bfebd8b29f7917ebe214c308e33b0b65f6c94f6 Mon Sep 17 00:00:00 2001
From: Noah Friedman <speelbarrow@speely.net>
Date: Wed, 27 Nov 2024 00:39:49 -0500
Subject: [PATCH] Implement `try-init` feature

---
 esp-hal/CHANGELOG.md      |  1 +
 esp-hal/Cargo.toml        |  4 ++++
 esp-hal/src/lib.rs        | 15 +++++++++++++++
 esp-hal/src/peripheral.rs | 19 +++++++++++++++++++
 hil-test/Cargo.toml       |  2 ++
 hil-test/tests/init.rs    |  7 +++++++
 6 files changed, 48 insertions(+)

diff --git a/esp-hal/CHANGELOG.md b/esp-hal/CHANGELOG.md
index 360c1427d71..4de91499b95 100644
--- a/esp-hal/CHANGELOG.md
+++ b/esp-hal/CHANGELOG.md
@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `esp_hal::psram::psram_raw_parts` (#2546)
 - The timer drivers `OneShotTimer` & `PeriodicTimer` have `into_async` and `new_typed` methods (#2586)
 - `timer::Timer` trait has three new methods, `wait`, `async_interrupt_handler` and `peripheral_interrupt` (#2586)
+- Add `try_init` function behind non-default feature `try-init` (#2618)
 
 ### Changed
 
diff --git a/esp-hal/Cargo.toml b/esp-hal/Cargo.toml
index 68ab0ade890..154ea8f40b7 100644
--- a/esp-hal/Cargo.toml
+++ b/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"
 
diff --git a/esp-hal/src/lib.rs b/esp-hal/src/lib.rs
index aafe8b21ea8..b689d6844f0 100644
--- a/esp-hal/src/lib.rs
+++ b/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
+    }
+}
diff --git a/esp-hal/src/peripheral.rs b/esp-hal/src/peripheral.rs
index 4a817111a84..5d55dbec1a0 100644
--- a/esp-hal/src/peripheral.rs
+++ b/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;
diff --git a/hil-test/Cargo.toml b/hil-test/Cargo.toml
index cc273714e98..186152cb1c4 100644
--- a/hil-test/Cargo.toml
+++ b/hil-test/Cargo.toml
@@ -297,6 +297,8 @@ integrated-timers = [
     "esp-hal-embassy/integrated-timers",
 ]
 octal-psram = ["esp-hal/octal-psram", "esp-alloc"]
+# `try-init`:
+try-init = ["esp-hal/try-init"]
 
 # https://doc.rust-lang.org/cargo/reference/profiles.html#test
 # Test and bench profiles inherit from dev and release respectively.
diff --git a/hil-test/tests/init.rs b/hil-test/tests/init.rs
index cec885c7319..d255073a58d 100644
--- a/hil-test/tests/init.rs
+++ b/hil-test/tests/init.rs
@@ -107,4 +107,11 @@ mod tests {
         let delay = Delay::new();
         delay.delay(2000.millis());
     }
+
+    #[cfg(feature = "try-init")]
+    #[test]
+    fn test_try_init() {
+        assert!(esp_hal::try_init(Config::default()).is_some());
+        assert!(esp_hal::try_init(Config::default()).is_none());
+    }
 }