Add new InterruptNumber trait

1 files changed, 21 insertions, 2 deletions

diff --git a/src/interrupt.rs b/src/interrupt.rs
index 4d5ef0f..c5da48d 100644
--- a/src/interrupt.rs
+++ b/src/interrupt.rs
@@ -1,8 +1,27 @@
 //! Interrupts
 
-// use core::sync::atomic::{self, Ordering};
+pub use bare_metal::{CriticalSection, Mutex};
 
-pub use bare_metal::{CriticalSection, Mutex, Nr};
+/// Trait for enums of external interrupt numbers.
+///
+/// This trait should be implemented by a peripheral access crate (PAC)
+/// on its enum of available external interrupts for a specific device.
+/// Each variant must convert to a u16 of its interrupt number,
+/// which is its exception number - 16.
+///
+/// # Safety
+///
+/// This trait must only be implemented on enums of device interrupts. Each
+/// enum variant must represent a distinct value (no duplicates are permitted),
+/// and must always return the same value (do not change at runtime).
+///
+/// These requirements ensure safe nesting of critical sections.
+pub unsafe trait InterruptNumber: Copy {
+    /// Return the interrupt number associated with this variant.
+    ///
+    /// See trait documentation for safety requirements.
+    fn number(self) -> u16;
+}
 
 /// Disables all interrupts
 #[inline]