zephyr: device: uart: Fix lifetimes of 'inner' method on UartIrq

This method had a lifetime error, and allowed the inner uart to be
leaked beyond its lifetime.

This should prevent the returned device from outliving the UartIrq, or
even being used after mutable methods on the UartIrq have been used.
For now, don't even return a mutable method until we evaluate what
should be permissible.  This at least allows reading the line status.

In addition, since the return Uart is not owned by the caller, it is not
permissible to call any of the `into_*` methods.

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

Author: d3zd3z

zephyr/src/device/uart.rs

@@ -209,6 +209,8 @@ pub struct UartIrq {
     device: *const raw::device,
     /// Critical section protected data.
     data: Arc<IrqOuterData>,
+    /// Interior wrapped device, to be able to hand out lifetime managed references to it.
+    uart: Uart,
 }
 
 // UartIrq is also Send, !Sync, for the same reasons as for Uart.
@@ -243,14 +245,16 @@ impl UartIrq {
         Ok(UartIrq {
             device: uart.device,
             data,
+            uart,
         })
     }
 
     /// Get the underlying UART to be able to change line control and such.
-    pub unsafe fn inner(&mut self) -> Uart {
-        Uart {
-            device: self.device
-        }
+    ///
+    /// TODO: This really should return something like `&Uart` to bind the lifetime.  Otherwise the
+    /// user can continue to use the uart handle beyond the lifetime of the driver.
+    pub unsafe fn inner(&mut self) -> &Uart {
+        &self.uart
     }
 
     /// Attempt to read data from the UART into the buffer.  If no data is available, it will