Adding a limit that async HALs can read and have as max prio

rtic-macros/src/analyze.rs

@@ -11,6 +11,7 @@ use syn::Ident;
 pub struct Analysis {
     parent: analyze::Analysis,
     pub interrupts: BTreeMap<Priority, (Ident, Dispatcher)>,
+    pub max_async_prio: Option<u8>,
 }
 
 impl ops::Deref for Analysis {
@@ -42,8 +43,16 @@ pub fn app(analysis: analyze::Analysis, app: &App) -> Analysis {
         .map(|p| (p, available_interrupt.pop().expect("UNREACHABLE")))
         .collect();
 
+    let max_async_prio = app
+        .hardware_tasks
+        .iter()
+        .map(|(_, task)| task.args.priority)
+        .min()
+        .map(|v| v - 1); // One less than the smallest HW task
+
     Analysis {
         parent: analysis,
         interrupts,
+        max_async_prio,
     }
 }

rtic-macros/src/codegen.rs

@@ -45,6 +45,7 @@ pub fn app(app: &App, analysis: &Analysis) -> TokenStream2 {
     let device = &app.args.device;
 
     let rt_err = util::rt_err_ident();
+    let async_limit = bindings::async_prio_limit(app, analysis);
 
     quote!(
         /// The RTIC application module
@@ -52,6 +53,8 @@ pub fn app(app: &App, analysis: &Analysis) -> TokenStream2 {
             /// Always include the device crate which contains the vector table
             use #device as #rt_err;
 
+            #(#async_limit)*
+
             #(#user_imports)*
 
             #(#user_code)*

rtic-macros/src/codegen/bindings/cortex.rs

@@ -322,3 +322,19 @@ pub fn interrupt_entry(_app: &App, _analysis: &CodegenAnalysis) -> Vec<TokenStre
 pub fn interrupt_exit(_app: &App, _analysis: &CodegenAnalysis) -> Vec<TokenStream2> {
     vec![]
 }
+
+pub fn async_prio_limit(app: &App, analysis: &CodegenAnalysis) -> Vec<TokenStream2> {
+    let max = if let Some(max) = analysis.max_async_prio {
+        quote!(#max)
+    } else {
+        // No limit
+        let device = &app.args.device;
+        quote!(1 << #device::NVIC_PRIO_BITS)
+    };
+
+    vec![quote!(
+        /// Holds the maximum priority level for use by async HAL drivers.
+        #[no_mangle]
+        static RTIC_ASYNC_MAX_LOGICAL_PRIO: u8 = #max;
+    )]
+}

rtic-macros/src/codegen/bindings/template.rs

@@ -42,3 +42,7 @@ pub fn interrupt_entry(_app: &App, _analysis: &CodegenAnalysis) -> Vec<TokenStre
 pub fn interrupt_exit(_app: &App, _analysis: &CodegenAnalysis) -> Vec<TokenStream2> {
     vec![]
 }
+
+pub fn async_prio_limit(app: &App, _analysis: &CodegenAnalysis) -> Vec<TokenStream2> {
+    vec![]
+}