While we already have the `warn_on` macro, a common usage patterns in
Rust is to check whether a `Result` is an error. Add a helper macro that
allows this.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 rust/kernel/bug.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs
index 36aef43e5ebe..255c780bb4f7 100644
--- a/rust/kernel/bug.rs
+++ b/rust/kernel/bug.rs
@@ -124,3 +124,13 @@ macro_rules! warn_on {
         cond
     }};
 }
+
+/// Report a warning if `res` is an error and return it unmodified.
+#[macro_export]
+macro_rules! warn_on_err {
+    ($res:expr) => {{
+        let res = $res;
+        let _ = $crate::warn_on!(res.is_err());
+        res
+    }};
+}

-- 
2.52.0