linux-kernel - Re: [PATCH v5 04/23] rust: add new `num` module with `PowerOfTwo` type

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Message-Id: <DANP8VIXMJ0Y.3U3ZP64DCB1ZM@nvidia.com>
Date: Mon, 16 Jun 2025 14:13:56 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "Miguel Ojeda" <miguel.ojeda.sandonis@...il.com>
Cc: "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>, "Andreas Hindborg" <a.hindborg@...nel.org>,
 "Alice Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>,
 "Danilo Krummrich" <dakr@...nel.org>, "David Airlie" <airlied@...il.com>,
 "Simona Vetter" <simona@...ll.ch>, "Maarten Lankhorst"
 <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "Benno Lossin"
 <lossin@...nel.org>, "John Hubbard" <jhubbard@...dia.com>, "Ben Skeggs"
 <bskeggs@...dia.com>, "Joel Fernandes" <joelagnelf@...dia.com>, "Timur
 Tabi" <ttabi@...dia.com>, "Alistair Popple" <apopple@...dia.com>,
 <linux-kernel@...r.kernel.org>, <rust-for-linux@...r.kernel.org>,
 <nouveau@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v5 04/23] rust: add new `num` module with `PowerOfTwo`
 type

On Sun Jun 15, 2025 at 10:32 PM JST, Miguel Ojeda wrote:
> On Thu, Jun 12, 2025 at 4:02 PM Alexandre Courbot <acourbot@...dia.com> wrote:
>>
>> +                /// assert_eq!(PowerOfTwo::<u32>::try_new(16).unwrap().value(), 16);
>
> By the way, we are trying to write examples close to normal kernel
> code as possible, so could you please use `?` here instead of
> `unwrap()`?
>
> It is not a big deal, when within `assert`s, but there is value in not
> showing any `unwrap()`s, and to spot easily places where we actually
> do `unwrap()`.

The fact that `try_new` returns an `Option` makes it a bit difficult to do
nicely - one would have to add a verbose `ok_or` to turn it into a
`Result`.

But that doesn't matter as this test can be (better) written as follows:

    assert_eq!(PowerOfTwo::<u32>::try_new(16), Some(PowerOfTwo::<u32>::new(16)));

And all is well.

> Also, please use intra-doc links wherever they may work, e.g. I think
> [`PowerOfTwo`] and [`None`] will work.

Added the links where relevant, sorry for the omission!