From 675b7fb6056d8c3dfaca759b7cd373e2f4a0e111 Mon Sep 17 00:00:00 2001
From: Dániel Buga <bugadani@gmail.com>
Date: Sat, 12 Aug 2023 16:00:18 +0200
Subject: POC: allow custom executors

---
 embassy-executor/src/thread.rs | 80 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 embassy-executor/src/thread.rs

(limited to 'embassy-executor/src/thread.rs')

diff --git a/embassy-executor/src/thread.rs b/embassy-executor/src/thread.rs
new file mode 100644
index 000000000..9bbe29500
--- /dev/null
+++ b/embassy-executor/src/thread.rs
@@ -0,0 +1,80 @@
+//! Thread-mode executor.
+
+use core::marker::PhantomData;
+
+use crate::raw::{OpaqueThreadContext, Pender, PenderInner};
+use crate::{raw, Spawner};
+
+/// TODO
+// Name pending
+pub trait ThreadContext: Sized {
+    /// TODO
+    fn context(&self) -> OpaqueThreadContext;
+
+    /// TODO
+    fn wait(&mut self);
+}
+
+/// Thread mode executor, using WFE/SEV.
+///
+/// This is the simplest and most common kind of executor. It runs on
+/// thread mode (at the lowest priority level), and uses the `WFE` ARM instruction
+/// to sleep when it has no more work to do. When a task is woken, a `SEV` instruction
+/// is executed, to make the `WFE` exit from sleep and poll the task.
+///
+/// This executor allows for ultra low power consumption for chips where `WFE`
+/// triggers low-power sleep without extra steps. If your chip requires extra steps,
+/// you may use [`raw::Executor`] directly to program custom behavior.
+pub struct ThreadModeExecutor<C: ThreadContext> {
+    inner: raw::Executor,
+    context: C,
+    not_send: PhantomData<*mut ()>,
+}
+
+impl<C: ThreadContext> ThreadModeExecutor<C> {
+    /// Create a new Executor.
+    pub fn new() -> Self
+    where
+        C: Default,
+    {
+        Self::with_context(C::default())
+    }
+
+    /// Create a new Executor.
+    pub fn with_context(context: C) -> Self {
+        Self {
+            inner: raw::Executor::new(Pender(PenderInner::Thread(context.context()))),
+            context,
+            not_send: PhantomData,
+        }
+    }
+
+    /// Run the executor.
+    ///
+    /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+    /// this executor. Use it to spawn the initial task(s). After `init` returns,
+    /// the executor starts running the tasks.
+    ///
+    /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+    /// for example by passing it as an argument to the initial tasks.
+    ///
+    /// This function requires `&'static mut self`. This means you have to store the
+    /// Executor instance in a place where it'll live forever and grants you mutable
+    /// access. There's a few ways to do this:
+    ///
+    /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+    /// - a `static mut` (unsafe)
+    /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+    ///
+    /// This function never returns.
+    pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+        init(self.inner.spawner());
+
+        loop {
+            unsafe {
+                self.inner.poll();
+                self.context.wait();
+            };
+        }
+    }
+}
-- 
cgit