From eedb51bbb63677f53cfdfb4d0e342981a4866df7 Mon Sep 17 00:00:00 2001
From: Dario Nieuwenhuis <dirbaio@dirbaio.net>
Date: Fri, 26 Mar 2021 23:20:27 +0100
Subject: [PATCH] extras: add Peripheral with shared state (like
 PeripheralMutex but without mutex)

---
 embassy-extras/src/lib.rs               |  1 +
 embassy-extras/src/peripheral_shared.rs | 68 +++++++++++++++++++++++++
 2 files changed, 69 insertions(+)
 create mode 100644 embassy-extras/src/peripheral_shared.rs

diff --git a/embassy-extras/src/lib.rs b/embassy-extras/src/lib.rs
index 5dafba702..be08ddf1e 100644
--- a/embassy-extras/src/lib.rs
+++ b/embassy-extras/src/lib.rs
@@ -5,6 +5,7 @@ pub(crate) mod fmt;
 
 mod macros;
 pub mod peripheral;
+pub mod peripheral_shared;
 pub mod ring_buffer;
 pub mod usb;
 
diff --git a/embassy-extras/src/peripheral_shared.rs b/embassy-extras/src/peripheral_shared.rs
new file mode 100644
index 000000000..73906698e
--- /dev/null
+++ b/embassy-extras/src/peripheral_shared.rs
@@ -0,0 +1,68 @@
+use core::cell::UnsafeCell;
+use core::marker::{PhantomData, PhantomPinned};
+use core::pin::Pin;
+use core::sync::atomic::{compiler_fence, Ordering};
+
+use embassy::interrupt::{Interrupt, InterruptExt};
+
+pub trait PeripheralState {
+    type Interrupt: Interrupt;
+    fn on_interrupt(&self);
+}
+
+pub struct Peripheral<S: PeripheralState> {
+    state: UnsafeCell<S>,
+
+    irq_setup_done: bool,
+    irq: S::Interrupt,
+
+    _not_send: PhantomData<*mut ()>,
+    _pinned: PhantomPinned,
+}
+
+impl<S: PeripheralState> Peripheral<S> {
+    pub fn new(irq: S::Interrupt, state: S) -> Self {
+        Self {
+            irq,
+            irq_setup_done: false,
+
+            state: UnsafeCell::new(state),
+            _not_send: PhantomData,
+            _pinned: PhantomPinned,
+        }
+    }
+
+    pub fn register_interrupt(self: Pin<&mut Self>) {
+        let this = unsafe { self.get_unchecked_mut() };
+        if this.irq_setup_done {
+            return;
+        }
+
+        this.irq.disable();
+        compiler_fence(Ordering::SeqCst);
+
+        this.irq.set_handler(|p| {
+            let state = unsafe { &*(p as *const S) };
+            state.on_interrupt();
+        });
+        this.irq
+            .set_handler_context((&this.state) as *const _ as *mut ());
+
+        compiler_fence(Ordering::SeqCst);
+        this.irq.enable();
+
+        this.irq_setup_done = true;
+    }
+
+    pub fn state(self: Pin<&mut Self>) -> &S {
+        let this = unsafe { self.get_unchecked_mut() };
+        unsafe { &*this.state.get() }
+    }
+}
+
+impl<S: PeripheralState> Drop for Peripheral<S> {
+    fn drop(&mut self) {
+        self.irq.disable();
+        self.irq.remove_handler();
+    }
+}