linux-kernel - Re: [PATCH v2 4/4] rust: sync: update integer types in CondVar

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Date: Mon, 18 Dec 2023 08:33:43 +0000
From: Tiago Lam <tiagolam@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>, Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>,
 Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng
 <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <benno.lossin@...ton.me>,
 Andreas Hindborg <a.hindborg@...sung.com>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
 Thomas Gleixner <tglx@...utronix.de>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] rust: sync: update integer types in CondVar

On 16/12/2023 15:31, Alice Ryhl wrote:
> Reduce the chances of compilation failures due to integer type
> mismatches in `CondVar`.
> 
> When an integer is defined using a #define in C, bindgen doesn't know
> which integer type it is supposed to be, so it will just use `u32` by
> default (if it fits in an u32). Whenever the right type is something
> else, we insert a cast in Rust. However, this means that the code has a
> lot of extra casts, and sometimes the code will be missing casts if u32
> happens to be correct on the developer's machine, even though the type
> might be something else on a different platform.
> 
> This patch updates all uses of such constants in
> `rust/kernel/sync/condvar.rs` to use constants defined with the right
> type. This allows us to remove various unnecessary casts, while also
> future-proofing for the case where `unsigned int != u32`.
> 
> I wrote this patch at the suggestion of Benno in [1].
> 
> Link: https://lore.kernel.org/all/nAEg-6vbtX72ZY3oirDhrSEf06TBWmMiTt73EklMzEAzN4FD4mF3TPEyAOxBZgZtjzoiaBYtYr3s8sa9wp1uYH9vEWRf2M-Lf4I0BY9rAgk=@proton.me/ [1]
> Suggested-by: Benno Lossin <benno.lossin@...ton.me>
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>

Reviewed-by: Tiago Lam <tiagolam@...il.com>