Merge #402

402: Extern task r=AfoHT a=perlindgren

Allows hardware and software task to be externally declared.

CI test, don't merge yet (squash needed).

Co-authored-by: Per Lindgren <per.lindgren@ltu.se>

CHANGELOG.md

@@ -13,6 +13,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   - `#[task_local]`, there must be only one task, similar to a task local
     resource, but (optionally) set-up by init. This is similar to move.
 
+- Improved ergonomics allowing separation of task signatures to actual implementation in extern block `extern "Rust" { #[task(..)] fn t(..); }`.
+
 ### Changed
 
 - [breaking-change] [PR 400] Move dispatchers from extern block to app argument.

book/en/src/migration/migration_v5.md

@@ -36,7 +36,6 @@ mod app {
 
 This works also for ram functions, see examples/ramfunc.rs
 
-
 ## Module instead of Const
 
 With the support of attributes on modules the `const APP` workaround is not needed.
@@ -125,3 +124,13 @@ struct whateveryouwant {
 ```
 
 would work equally well.
+
+---
+
+## Additions
+
+### Extern tasks
+
+Both software and hardware tasks can now be defined external to the `mod app`. Previously this was possible only by implementing a trampoline calling out the task implementation.  
+
+See examples `examples/extern_binds.rs` and `examples/extern_spawn.rs`.

examples/extern_binds.rs

@@ -0,0 +1,48 @@
+//! examples/extern_binds.rs
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+use cortex_m_semihosting::hprintln;
+use panic_semihosting as _;
+
+// Free function implementing the interrupt bound task `foo`.
+fn foo(_: app::foo::Context) {
+    hprintln!("foo called").ok();
+}
+
+#[rtic::app(device = lm3s6965)]
+mod app {
+    use crate::foo;
+    use cortex_m_semihosting::{debug, hprintln};
+    use lm3s6965::Interrupt;
+
+    #[init]
+    fn init(_: init::Context) -> init::LateResources {
+        rtic::pend(Interrupt::UART0);
+
+        hprintln!("init").unwrap();
+
+        init::LateResources {}
+    }
+
+    #[idle]
+    fn idle(_: idle::Context) -> ! {
+        hprintln!("idle").unwrap();
+
+        rtic::pend(Interrupt::UART0);
+
+        debug::exit(debug::EXIT_SUCCESS);
+
+        loop {
+            cortex_m::asm::nop();
+        }
+    }
+
+    extern "Rust" {
+        #[task(binds = UART0)]
+        fn foo(_: foo::Context);
+    }
+}

examples/extern_spawn.rs

@@ -0,0 +1,35 @@
+//! examples/extern_spawn.rs
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+use cortex_m_semihosting::{debug, hprintln};
+use panic_semihosting as _;
+
+// Free function implementing the spawnable task `foo`.
+fn foo(_c: app::foo::Context, x: i32, y: u32) {
+    hprintln!("foo {}, {}", x, y).unwrap();
+    if x == 2 {
+        debug::exit(debug::EXIT_SUCCESS);
+    }
+    app::foo::spawn(2, 3).unwrap();
+}
+
+#[rtic::app(device = lm3s6965, dispatchers = [SSI0])]
+mod app {
+    use crate::foo;
+
+    #[init]
+    fn init(_c: init::Context) -> init::LateResources {
+        foo::spawn(1, 2).unwrap();
+
+        init::LateResources {}
+    }
+
+    extern "Rust" {
+        #[task()]
+        fn foo(_c: foo::Context, _x: i32, _y: u32);
+    }
+}

macros/src/codegen/hardware_tasks.rs

@@ -95,6 +95,7 @@ pub fn codegen(
             locals_pat = Some(pat);
         }
 
+        if !&task.is_extern {
             let attrs = &task.attrs;
             let context = &task.context;
             let stmts = &task.stmts;
@@ -109,6 +110,7 @@ pub fn codegen(
                 }
             ));
         }
+    }
 
     (mod_app, root, user_tasks)
 }

macros/src/codegen/software_tasks.rs

@@ -99,6 +99,7 @@ pub fn codegen(
             root.push(struct_);
         }
 
+        if !&task.is_extern {
             let context = &task.context;
             let attrs = &task.attrs;
             let cfgs = &task.cfgs;
@@ -114,6 +115,7 @@ pub fn codegen(
                     #(#stmts)*
                 }
             ));
+        }
 
         root.push(module::codegen(
             Context::SoftwareTask(name),

ui/single/extern-interrupt-used.rs

@@ -4,8 +4,4 @@
 mod app {
     #[task(binds = UART0)]
     fn a(_: a::Context) {}
-
-    extern "C" {
-        fn UART0();
-    }
 }