linux-kernel - [PATCH v2 4/7] rust: bits: always inline functions using build

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Message-Id: <20251128-io-build-assert-v2-4-a9ea9ce7d45d@nvidia.com>
Date: Fri, 28 Nov 2025 11:11:40 +0900
From: Alexandre Courbot <acourbot@...dia.com>
To: Danilo Krummrich <dakr@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Daniel Almeida <daniel.almeida@...labora.com>, 
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
 Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>, 
 Trevor Gross <tmgross@...ch.edu>, "Rafael J. Wysocki" <rafael@...nel.org>, 
 Viresh Kumar <viresh.kumar@...aro.org>, Will Deacon <will@...nel.org>, 
 Peter Zijlstra <peterz@...radead.org>, Mark Rutland <mark.rutland@....com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-pm@...r.kernel.org, Alexandre Courbot <acourbot@...dia.com>
Subject: [PATCH v2 4/7] rust: bits: always inline functions using
 build_assert with arguments

`build_assert` relies on the compiler to optimize out its error path.
Functions using it with its arguments must thus always be inlined,
otherwise the error path of `build_assert` might not be optimized out,
triggering a build error.

Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
---
 rust/kernel/bits.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/bits.rs b/rust/kernel/bits.rs
index 553d50265883..2daead125626 100644
--- a/rust/kernel/bits.rs
+++ b/rust/kernel/bits.rs
@@ -27,7 +27,8 @@ pub fn [<checked_bit_ $ty>](n: u32) -> Option<$ty> {
             ///
             /// This version is the default and should be used if `n` is known at
             /// compile time.
-            #[inline]
+            // Always inline to optimize out error path of `build_assert`.
+            #[inline(always)]
             pub const fn [<bit_ $ty>](n: u32) -> $ty {
                 build_assert!(n < <$ty>::BITS);
                 (1 as $ty) << n
@@ -75,7 +76,8 @@ pub fn [<genmask_checked_ $ty>](range: RangeInclusive<u32>) -> Option<$ty> {
             /// This version is the default and should be used if the range is known
             /// at compile time.
             $(#[$genmask_ex])*
-            #[inline]
+            // Always inline to optimize out error path of `build_assert`.
+            #[inline(always)]
             pub const fn [<genmask_ $ty>](range: RangeInclusive<u32>) -> $ty {
                 let start = *range.start();
                 let end = *range.end();

-- 
2.52.0