linux-kernel - [PATCH v14 3/9] rust: Add missing SAFETY documentation for `ARef` example

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Message-Id: <20260204-unique-ref-v14-3-17cb29ebacbb@kernel.org>
Date: Wed, 04 Feb 2026 12:56:47 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Miguel Ojeda <ojeda@...nel.org>, Boqun Feng <boqun.feng@...il.com>, 
 Gary Guo <gary@...yguo.net>, 
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
 Benno Lossin <lossin@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Dave Ertman <david.m.ertman@...el.com>, Ira Weiny <ira.weiny@...el.com>, 
 Leon Romanovsky <leon@...nel.org>, Paul Moore <paul@...l-moore.com>, 
 Serge Hallyn <sergeh@...nel.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Alexander Viro <viro@...iv.linux.org.uk>, 
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
 Igor Korotin <igor.korotin.linux@...il.com>, 
 Daniel Almeida <daniel.almeida@...labora.com>, 
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
 Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>, 
 Stephen Boyd <sboyd@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
 Krzysztof Wilczyński <kwilczynski@...nel.org>
Cc: linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org, 
 linux-block@...r.kernel.org, linux-security-module@...r.kernel.org, 
 dri-devel@...ts.freedesktop.org, linux-fsdevel@...r.kernel.org, 
 linux-mm@...ck.org, linux-pm@...r.kernel.org, linux-pci@...r.kernel.org, 
 Andreas Hindborg <a.hindborg@...nel.org>, 
 Oliver Mangold <oliver.mangold@...me>
Subject: [PATCH v14 3/9] rust: Add missing SAFETY documentation for `ARef`
 example

From: Oliver Mangold <oliver.mangold@...me>

SAFETY comment in rustdoc example was just 'TODO'. Fixed.

Original patch by Oliver Mangold <oliver.mangold@...me> [1].

Link: https://lore.kernel.org/r/20251117-unique-ref-v13-3-b5b243df1250@pm.me [1]
Reviewed-by: Daniel Almeida <daniel.almeida@...labora.com>
Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
---
 rust/kernel/sync/aref.rs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index 61caddfd89619..efe16a7fdfa5d 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -129,12 +129,14 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
     /// # Examples
     ///
     /// ```
-    /// use core::ptr::NonNull;
-    /// use kernel::sync::aref::{ARef, RefCounted};
+    /// # use core::ptr::NonNull;
+    /// # use kernel::sync::aref::{ARef, RefCounted};
     ///
     /// struct Empty {}
     ///
-    /// # // SAFETY: TODO.
+    /// // SAFETY: The `RefCounted` implementation for `Empty` does not count references and never
+    /// // frees the underlying object. Thus we can act as owning an increment on the refcount for
+    /// // the object that we pass to the newly created `ARef`.
     /// unsafe impl RefCounted for Empty {
     ///     fn inc_ref(&self) {}
     ///     unsafe fn dec_ref(_obj: NonNull<Self>) {}
@@ -142,7 +144,7 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
     ///
     /// let mut data = Empty {};
     /// let ptr = NonNull::<Empty>::new(&mut data).unwrap();
-    /// # // SAFETY: TODO.
+    /// // SAFETY: We keep `data` around longer than the `ARef`.
     /// let data_ref: ARef<Empty> = unsafe { ARef::from_raw(ptr) };
     /// let raw_ptr: NonNull<Empty> = ARef::into_raw(data_ref);
     ///

-- 
2.51.2