linux-kernel - Re: [PATCH 1/7] drm/panic: avoid reimplementing Iterator::find

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Message-ID: <89f24f92-de2d-4303-a189-9e5bc1eba02a@redhat.com>
Date: Mon, 14 Oct 2024 10:44:56 +0200
From: Jocelyn Falempe <jfalempe@...hat.com>
To: Thomas Böhler <witcher@...edspace.de>,
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>
Cc: 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>, Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>, rust-for-linux@...r.kernel.org,
 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>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] drm/panic: avoid reimplementing Iterator::find

On 12/10/2024 09:52, Thomas Böhler wrote:
> Rust's standard library's `std::iter::Iterator` trait provides a function
> `find` that finds the first element that satisfies a predicate.
> The function `Version::from_segments` is doing the same thing but is
> implementing the same logic itself.
> Clippy complains about this in the `manual_find` lint:
> 
>      error: manual implementation of `Iterator::find`
>         --> drivers/gpu/drm/drm_panic_qr.rs:212:9
>          |
>      212 | /         for v in (1..=40).map(|k| Version(k)) {
>      213 | |             if v.max_data() * 8 >= segments.iter().map(|s| s.total_size_bits(v)).sum() {
>      214 | |                 return Some(v);
>      215 | |             }
>      216 | |         }
>      217 | |         None
>          | |____________^ help: replace with an iterator: `(1..=40).map(|k| Version(k)).find(|&v| v.max_data() * 8 >= segments.iter().map(|s| s.total_size_bits(v)).sum())`
>          |
>          = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_find
>          = note: `-D clippy::manual-find` implied by `-D warnings`
>          = help: to override `-D warnings` add `#[allow(clippy::manual_find)]`
> 
> Use `Iterator::find` instead to make the intention clearer.

Thanks for this patch, and the whole series.

It's a nice cleanup.

Reviewed-by: Jocelyn Falempe <jfalempe@...hat.com>

-- 

Jocelyn


> 
> Reported-by: Miguel Ojeda <ojeda@...nel.org>
> Closes: https://github.com/Rust-for-Linux/linux/issues/1123
> Signed-off-by: Thomas Böhler <witcher@...edspace.de>
> ---
>   drivers/gpu/drm/drm_panic_qr.rs | 9 +++------
>   1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_panic_qr.rs b/drivers/gpu/drm/drm_panic_qr.rs
> index 1ef56cb07dfb..76decf49e678 100644
> --- a/drivers/gpu/drm/drm_panic_qr.rs
> +++ b/drivers/gpu/drm/drm_panic_qr.rs
> @@ -209,12 +209,9 @@
>   impl Version {
>       /// Returns the smallest QR version than can hold these segments.
>       fn from_segments(segments: &[&Segment<'_>]) -> Option<Version> {
> -        for v in (1..=40).map(|k| Version(k)) {
> -            if v.max_data() * 8 >= segments.iter().map(|s| s.total_size_bits(v)).sum() {
> -                return Some(v);
> -            }
> -        }
> -        None
> +        (1..=40)
> +            .map(Version)
> +            .find(|&v| v.max_data() * 8 >= segments.iter().map(|s| s.total_size_bits(v)).sum())
>       }
>   
>       fn width(&self) -> u8 {