[PATCH v3 1/6] rust: add warn_on_err macro

[Alexandre Courbot <acourbot@nvidia.com>]

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

Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
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 ed943960f851..c5809c554da7 100644
--- a/rust/kernel/bug.rs
+++ b/rust/kernel/bug.rs
@@ -130,3 +130,13 @@ macro_rules! warn_on {
         cond
     }};
 }
+
+/// Report a warning if `res` is an error and return `res` unmodified.
+#[macro_export]
+macro_rules! warn_on_err {
+    ($res:expr) => {{
+        let res = $res;
+        let _ = $crate::warn_on!(res.is_err());
+        res
+    }};
+}

-- 
2.53.0