document set_fpu_access_mode footgun

closes #44
rust-embedded · Dec 21, 2017 · 9a80bae · 9a80bae
1 parent 4689992
commit 9a80bae
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/src/peripheral/scb.rs b/src/peripheral/scb.rs
@@ -78,6 +78,11 @@ impl RegisterBlock {
  }
 
  /// Sets FPU access mode
+ ///
+ /// *IMPORTANT* Any function that runs fully or partly with the FPU disabled must *not* take any
+ /// floating-point arguments or have any floating-point local variables. Because the compiler
+ /// might inline such a function into a caller that does have floating-point arguments or
+ /// variables, any such function must be also marked #[inline(never)].
  pub fn set_fpu_access_mode(&self, mode: FpuAccessMode) {
  let mut cpacr = self.cpacr.read() & !SCB_CPACR_FPU_MASK;
  match mode {