Implement esp_hal::try_init API

esp-hal/CHANGELOG.md

@@ -22,6 +22,8 @@ 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)
+- Improve safety for verifying `init` is only called once, 
+  add `try_init` function for safely initializing peripheral when they may already have been (#2618)
 
 ### Changed
 

esp-hal/src/lib.rs

@@ -494,15 +494,7 @@ pub struct Config {
     pub psram: psram::PsramConfig,
 }
 
-/// Initialize the system.
-///
-/// This function sets up the CPU clock and watchdog, then, returns the
-/// peripherals and clocks.
-pub fn init(config: Config) -> Peripherals {
-    system::disable_peripherals();
-
-    let mut peripherals = Peripherals::take();
-
+fn init_internal<'a>(peripherals: &'a mut Peripherals, config: Config) {
     // RTC domain must be enabled before we try to disable
     let mut rtc = crate::rtc_cntl::Rtc::new(&mut peripherals.LPWR);
 
@@ -556,6 +548,34 @@ pub fn init(config: Config) -> Peripherals {
 
     #[cfg(any(feature = "quad-psram", feature = "octal-psram"))]
     crate::psram::init_psram(config.psram);
+}
 
-    peripherals
+/// Initialize the system.
+///
+/// This function sets up the CPU clock and watchdog, then, returns the
+/// peripherals and clocks.
+pub fn init(config: Config) -> Peripherals {
+    system::disable_peripherals();
+
+    if let Some(mut peripherals) = Peripherals::try_take() {
+        init_internal(&mut peripherals, config);
+        peripherals
+    } else {
+        panic!("init called more than once!");
+    }
+}
+
+/// Initializes the system only if necessary, then returns the peripherals.
+///
+/// If [`init`] has already been executed, simply steals and returns the
+/// peripherals. (This check uses [`AtomicBool`](core::sync::atomic::AtomicBool)
+/// to be as thread-safe as possible)
+///
+/// Otherwise, the initialization process is executed (and then the peripherals
+/// are stolen and handed off to you).
+pub unsafe fn try_init(config: Config) -> Peripherals {
+    if let Some(mut peripherals) = Peripherals::try_take() {
+        init_internal(&mut peripherals, config);
+    }
+    Peripherals::steal()
 }

esp-hal/src/peripheral.rs

@@ -257,9 +257,14 @@ mod peripheral_macros {
                 ),* $(,)?
             ]
         ) => {
+            use portable_atomic::Ordering;
+
 
             /// Contains the generated peripherals which implement [`Peripheral`]
             mod peripherals {
+                use portable_atomic::AtomicBool;
+                pub(crate) static INITIALIZED: AtomicBool = AtomicBool::new(false);
+
                 pub use super::pac::*;
                 $(
                     $crate::create_peripheral!($name <= $from_pac);
@@ -295,17 +300,13 @@ mod peripheral_macros {
                 impl Peripherals {
                     /// Returns all the peripherals *once*
                     #[inline]
-                    pub(crate) fn take() -> Self {
-                        #[no_mangle]
-                        static mut _ESP_HAL_DEVICE_PERIPHERALS: bool = false;
-
-                        critical_section::with(|_| unsafe {
-                            if _ESP_HAL_DEVICE_PERIPHERALS {
-                                panic!("init called more than once!")
-                            }
-                            _ESP_HAL_DEVICE_PERIPHERALS = true;
-                            Self::steal()
-                        })
+                    pub(crate) fn try_take() -> Option<Self> {
+                        if let Ok(_) = peripherals::INITIALIZED.compare_exchange(false, true,
+                            Ordering::Acquire, Ordering::Relaxed) {
+                            Some(unsafe { Self::steal() })
+                        } else {
+                            None
+                        }
                     }
 
                     /// Unsafely create an instance of this peripheral out of thin air.

hil-test/tests/init.rs

@@ -107,4 +107,19 @@ mod tests {
         let delay = Delay::new();
         delay.delay(2000.millis());
     }
+
+    #[test]
+    #[timeout(3)]
+    fn test_init_then_try_init() {
+        esp_hal::init(Config::default());
+
+        esp_hal::try_init(Config::default());
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_try_init_then_init() {
+        esp_hal::try_init(Config::default());
+        esp_hal::init(Config::default());
+    }
 }