Tweaks to appease semver-checks

Author: adamgreig

cortex-m/Cargo.toml

@@ -40,6 +40,8 @@ inline-asm = []
 linker-plugin-lto = []
 std = []
 critical-section-single-core = ["critical-section/restore-state-u32"]
+# Deprecated feature from when critical-section was an optional dependency
+critical-section = []
 
 [package.metadata.docs.rs]
 targets = [

cortex-m/src/interrupt.rs

@@ -74,9 +74,11 @@ where
     r
 }
 
-// Make a `free()` function available to allow checking dependencies without specifying a target,
-// but that will panic at runtime if executed.
-#[doc(hidden)]
+// Make a `free()` function available on hosted platforms to allow checking dependencies without
+// specifying a target, but that will panic at runtime if executed.
+/// Execute closure `f` in an interrupt-free context.
+///
+/// This as also known as a "critical section".
 #[cfg(not(cortex_m))]
 #[inline]
 pub fn free<F, R>(_: F) -> R

cortex-m/src/register/primask.rs

@@ -29,7 +29,6 @@ impl Primask {
 }
 
 /// Reads the prioritizable interrupt mask
-#[cfg(cortex_m)]
 #[inline]
 pub fn read() -> Primask {
     if read_raw() & (1 << 0) == (1 << 0) {
@@ -41,11 +40,15 @@ pub fn read() -> Primask {
 
 /// Reads the entire PRIMASK register
 /// Note that bits [31:1] are reserved and UNK (Unknown)
-#[cfg(cortex_m)]
 #[inline]
 pub fn read_raw() -> u32 {
     let r: u32;
-    unsafe { asm!("mrs {}, PRIMASK", out(reg) r, options(nomem, nostack, preserves_flags)) };
+    #[cfg(cortex_m)]
+    unsafe {
+        asm!("mrs {}, PRIMASK", out(reg) r, options(nomem, nostack, preserves_flags))
+    };
+    #[cfg(not(cortex_m))]
+    panic!("cannot read PRIMASK on non-cortex-m platform");
     r
 }