Merge #448

448: Add implementation for critical-section 1.0, for cortex-m v0.7.x r=adamgreig a=Dirbaio

This is a subset of #447 without any breaking changes, just adding the `critical-section` implementation.

The goal is to release it in 0.7.6 so `critical-section` becomes usable without having to wait for cortex-m 0.8.


TODO before merging:

- [x] Wait for `critical-section 1.0` release https://github.com/rust-embedded/critical-section/pull/19

Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>

2 files changed, 26 insertions, 0 deletions

diff --git a/src/critical_section.rs b/src/critical_section.rs
new file mode 100644
index 0000000..d33e90f
--- /dev/null
+++ b/src/critical_section.rs
@@ -0,0 +1,25 @@
+#[cfg(all(cortex_m, feature = "critical-section-single-core"))]
+mod single_core_critical_section {
+    use critical_section::{set_impl, Impl, RawRestoreState};
+
+    use crate::interrupt;
+    use crate::register::primask;
+
+    struct SingleCoreCriticalSection;
+    set_impl!(SingleCoreCriticalSection);
+
+    unsafe impl Impl for SingleCoreCriticalSection {
+        unsafe fn acquire() -> RawRestoreState {
+            let was_active = primask::read().is_active();
+            interrupt::disable();
+            was_active
+        }
+
+        unsafe fn release(was_active: RawRestoreState) {
+            // Only re-enable interrupts if they were enabled before the critical section.
+            if was_active {
+                interrupt::enable()
+            }
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 4790f98..1796b78 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -90,6 +90,7 @@ mod macros;
 pub mod asm;
 #[cfg(armv8m)]
 pub mod cmse;
+mod critical_section;
 pub mod delay;
 pub mod interrupt;
 #[cfg(all(not(armv6m), not(armv8m_base)))]