linux-kernel - Re: [PATCH v3 10/16] rust: block: add block related constants

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Message-Id: <8CD9F17A-0F1C-4EDC-A63D-F6A0EAC75F35@collabora.com>
Date: Wed, 6 Aug 2025 14:27:19 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: Boqun Feng <boqun.feng@...il.com>,
 Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>,
 Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <lossin@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>,
 Jens Axboe <axboe@...nel.dk>,
 linux-block@...r.kernel.org,
 rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 10/16] rust: block: add block related constants



> On 11 Jul 2025, at 08:43, Andreas Hindborg <a.hindborg@...nel.org> wrote:
> 
> Add a few block subsystem constants to the rust `kernel::block` name space.
> This makes it easier to access the constants from rust code.
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
> ---
> rust/kernel/block.rs | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
> 
> diff --git a/rust/kernel/block.rs b/rust/kernel/block.rs
> index 150f710efe5b..7461adf4d7e0 100644
> --- a/rust/kernel/block.rs
> +++ b/rust/kernel/block.rs
> @@ -3,3 +3,15 @@
> //! Types for working with the block layer.
> 
> pub mod mq;
> +
> +/// Bit mask for masking out [`SECTOR_SIZE`]

Missing period.

> +pub const SECTOR_MASK: u32 = bindings::SECTOR_MASK;
> +
> +/// Sectors are size `1 << SECTOR_SHIFT`.
> +pub const SECTOR_SHIFT: u32 = bindings::SECTOR_SHIFT;
> +
> +/// Size of a sector.
> +pub const SECTOR_SIZE: u32 = bindings::SECTOR_SIZE;
> +
> +/// Power of two difference in size of a page and size of a sector.

A bit hard to parse this.

Maybe “The difference between the size of a page and the size of a sector,
expressed as a power of two” ?

> +pub const PAGE_SECTORS_SHIFT: u32 = bindings::PAGE_SECTORS_SHIFT;
> 
> -- 
> 2.47.2
> 
> 
> 


 let sector: usize = something;
 let page_offset = (sector & block::SECTOR_MASK as usize) << block::SECTOR_SHIFT;


Wait, the parenthesis evaluate to usize, and the shift is a u32. How does this compile?

— Daniel