rust: types: implement ForeignOwnable for the unit type

This allows us to use the unit type `()` when we have no object whose ownership must be managed but one implementing the `ForeignOwnable` trait is needed. Signed-off-by: Wedson Almeida Filho <[email protected]> Reviewed-by: Vincenzo Palazzo <[email protected]> Reviewed-by: Gary Guo <[email protected]> Reviewed-by: Andreas Hindborg <[email protected]> Signed-off-by: Miguel Ojeda <[email protected]>
mj22226 · Feb 1, 2023 · 7118594 · 7118594
1 parent 26949ba
commit 7118594
Showing 1 changed file with 12 additions and 0 deletions.
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
@@ -85,6 +85,18 @@ impl<T: 'static> ForeignOwnable for Box<T> {
     }
 }
 
+impl ForeignOwnable for () {
+    type Borrowed<'a> = ();
+
+    fn into_foreign(self) -> *const core::ffi::c_void {
+        core::ptr::NonNull::dangling().as_ptr()
+    }
+
+    unsafe fn borrow<'a>(_: *const core::ffi::c_void) -> Self::Borrowed<'a> {}
+
+    unsafe fn from_foreign(_: *const core::ffi::c_void) -> Self {}
+}
+
 /// Runs a cleanup function/closure when dropped.
 ///
 /// The [`ScopeGuard::dismiss`] function prevents the cleanup function from running.