zephyr: sync: channel: Allow sending of raw messages

Add an unsafe entry to the channel code that allows the message to be
allocated previously.  This can be useful to send messages from
interrupt context, although the message has to be pre-allocate and given
to the interrupt handler.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

zephyr/src/sync/channel.rs

@@ -71,7 +71,10 @@ pub struct Message<T> {
 }
 
 impl<T> Message<T> {
-    fn new(data: T) -> Message<T> {
+    /// Construct a new message from the data.
+    ///
+    /// This is safe in itself, but sending them is unsafe.
+    pub fn new(data: T) -> Message<T> {
         Message {
             _private: 0,
             data,
@@ -99,6 +102,16 @@ impl<T> Sender<T> {
         }
         Ok(())
     }
+
+    /// Sends a message that has already been boxed.  The box will be dropped upon receipt.  This is
+    /// safe to call from interrupt context, and presumably the box will be allocate from a thread.
+    pub unsafe fn send_boxed(&self, msg: Box<Message<T>>) -> Result<(), SendError<T>> {
+        let msg = Box::into_raw(msg);
+        unsafe {
+            self.queue.send(msg as *mut c_void);
+        }
+        Ok(())
+    }
 }
 
 impl<T> Drop for Sender<T> {