Monotonic trait is safe; add MultiCore trait

src/cyccnt.rs

@@ -116,6 +116,11 @@ pub struct Duration {
 }
 
 impl Duration {
+    /// Creates a new `Duration` from the specified number of clock cycles
+    pub fn from_cycles(cycles: u32) -> Self {
+        Duration { inner: cycles }
+    }
+
     /// Returns the total number of clock cycles contained by this `Duration`
     pub fn as_cycles(&self) -> u32 {
         self.inner
@@ -181,7 +186,7 @@ impl U32Ext for u32 {
 pub struct CYCCNT;
 
 #[cfg(not(feature = "heterogeneous"))]
-unsafe impl crate::Monotonic for CYCCNT {
+impl crate::Monotonic for CYCCNT {
     type Instant = Instant;
 
     fn ratio() -> u32 {

src/export.rs

@@ -108,6 +108,13 @@ where
 {
 }
 
+#[inline(always)]
+pub fn assert_multicore<T>()
+where
+    T: super::MultiCore,
+{
+}
+
 #[cfg(armv7m)]
 #[inline(always)]
 pub unsafe fn lock<T, R>(

src/lib.rs

@@ -117,7 +117,7 @@ impl From<cortex_m::Peripherals> for Peripherals {
 }
 
 /// A monotonic clock / counter
-pub unsafe trait Monotonic {
+pub trait Monotonic {
     /// A measurement of this clock
     type Instant: Copy + Ord + Sub;
 
@@ -134,6 +134,9 @@ pub unsafe trait Monotonic {
     fn zero() -> Self::Instant;
 }
 
+/// A marker trait that indicates that it is correct to use this type in multi-core context
+pub trait MultiCore {}
+
 /// Sets the given `interrupt` as pending
 ///
 /// This is a convenience function around