linux-kernel - Re: [PATCH v5 05/23] rust: num: add the `fls` operation

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Message-ID: <CANiq72mpFX2pSuy7JU+Xb_6fCkEA96er6Rsg0bVv+wBBO5OqUw@mail.gmail.com>
Date: Sun, 15 Jun 2025 15:25:42 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Alexandre Courbot <acourbot@...dia.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 05/23] rust: num: add the `fls` operation

On Sun, Jun 15, 2025 at 12:58 PM Alexandre Courbot <acourbot@...dia.com> wrote:
>
> Also, although this will work nicely for `impl_fls!` which is a single
> function, I'm afraid this won't scale well for `power_of_two_impl!`,
> which defines 6 functions per type... Any suggestions for this case?

We can always generate the same "cases", i.e. sharing as much as
possible the lines, and just passing the values (numbers) that
actually differ, which you then plug into the example line
concatenating.

The standard library does that for their integer macros, e.g.

    https://doc.rust-lang.org/src/core/num/int_macros.rs.html#3639-3644

If that happened to be too onerous for some reason, then we could
ignore it for the time being (i.e. we don't need to delay things just
for that), or we could put them as `#[test]`s to at least have them as
tests.

Cheers,
Miguel