linux-kernel - Re: [PATCH 1/2] drm/panic: use `div

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Message-ID: <CAH5fLgjhMfk1vZCc242vKYnTN13Ss23VhVhaAjwU67Z5qhP9mA@mail.gmail.com>
Date: Mon, 3 Mar 2025 09:05:49 +0100
From: Alice Ryhl <aliceryhl@...gle.com>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: Jocelyn Falempe <jfalempe@...hat.com>, Thomas Böhler <witcher@...edspace.de>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Alex Gaynor <alex.gaynor@...il.com>, dri-devel@...ts.freedesktop.org, 
	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@...nel.org>, 
	Trevor Gross <tmgross@...ch.edu>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH 1/2] drm/panic: use `div_ceil` to clean Clippy warning

On Sun, Mar 2, 2025 at 12:17 AM Miguel Ojeda <ojeda@...nel.org> wrote:
>
> Starting with the upcoming Rust 1.86.0 (to be released 2025-04-03),
> Clippy warns:
>
>     error: manually reimplementing `div_ceil`
>        --> drivers/gpu/drm/drm_panic_qr.rs:548:26
>         |
>     548 |         let pad_offset = (offset + 7) / 8;
>         |                          ^^^^^^^^^^^^^^^^ help: consider using `.div_ceil()`: `offset.div_ceil(8)`
>         |
>         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_div_ceil
>
> And similarly for `stride`. Thus apply the suggestion to both.
>
> The behavior (and thus codegen) is not exactly equivalent [1][2], since
> `div_ceil()` returns the right value for the values that currently
> would overflow.
>
> Link: https://github.com/rust-lang/rust-clippy/issues/14333 [1]
> Link: https://godbolt.org/z/dPq6nGnv3 [2]
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>