Rewrite RNG

Author: bugadani

esp-hal/CHANGELOG.md

@@ -10,9 +10,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - A reimplemntation of the `assign_resources!` macro (#3809)
+- `TrngSource` to manage random number generator entropy (#3829)
 
 ### Changed
 
+- The `rng` module has been rewritten (#3829)
 
 ### Fixed
 
@@ -21,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Removed
 
+- `Trng::new` (replaced by `Trng::try_new`) (#3829)
 
 ## [v1.0.0-rc.0] - 2025-07-16
 

esp-hal/MIGRATING-1.0.0-rc.0.md

@@ -0,0 +1,26 @@
+# Migration Guide from 1.0.0-rc.0 to {{currentVersion}}
+
+## RNG changes
+
+Random number generator objects can now be created anywhere. The `RNG` peripheral singleton
+is only necessary to enable the cryptographically secure random number generator.
+
+ - `Rng` can be constructed without any constraints.
+ - `Trng` can only be constructed when it can be ensured to generate true random numbers.
+
+A new `TrngSource` object has been added. Users can use `TrngSource::new` to create the object,
+and as long as it is alive, `Trng::try_new` will return `Ok` and will provide a true random number
+generator interface.
+
+The previous way to obtain RNG object has changed like so:
+
+```diff
+-let mut rng = Rng::new(peripherals.RNG);
++let rng = Rng::new();
+
+-let mut trng = Trng::new(peripherals.RNG, peripherals.ADC1);
++// Once:
++let trng_source = TrngSource::new(peripherals.RNG, peripherals.ADC1);
++// As long as `trng_source` is alive:
++let trng = Tnrg::try_new().unrwap();
+```