1 files changed, 39 insertions, 0 deletions
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 67637b874267..5f4114b30b94 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -237,3 +237,42 @@ pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
     }
     Ok(ptr)
 }
+
+/// Calls a closure returning a [`crate::error::Result<T>`] and converts the result to
+/// a C integer result.
+///
+/// This is useful when calling Rust functions that return [`crate::error::Result<T>`]
+/// from inside `extern "C"` functions that need to return an integer error result.
+///
+/// `T` should be convertible from an `i16` via `From<i16>`.
+///
+/// # Examples
+///
+/// ```ignore
+/// # use kernel::from_result;
+/// # use kernel::bindings;
+/// unsafe extern "C" fn probe_callback(
+///     pdev: *mut bindings::platform_device,
+/// ) -> core::ffi::c_int {
+///     from_result(|| {
+///         let ptr = devm_alloc(pdev)?;
+///         bindings::platform_set_drvdata(pdev, ptr);
+///         Ok(0)
+///     })
+/// }
+/// ```
+// TODO: Remove `dead_code` marker once an in-kernel client is available.
+#[allow(dead_code)]
+pub(crate) fn from_result<T, F>(f: F) -> T
+where
+    T: From<i16>,
+    F: FnOnce() -> Result<T>,
+{
+    match f() {
+        Ok(v) => v,
+        // NO-OVERFLOW: negative `errno`s are no smaller than `-bindings::MAX_ERRNO`,
+        // `-bindings::MAX_ERRNO` fits in an `i16` as per invariant above,
+        // therefore a negative `errno` always fits in an `i16` and will not overflow.
+        Err(e) => T::from(e.to_errno() as i16),
+    }
+}