linux-kernel - Re: [PATCH v5 0/4] rust: adds Bitmap API, ID pool and bindings

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Message-ID: <Z914T_oYHvV_Zk74@thinkpad>
Date: Fri, 21 Mar 2025 10:31:43 -0400
From: Yury Norov <yury.norov@...il.com>
To: Burak Emir <bqe@...gle.com>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	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>,
	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, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/4] rust: adds Bitmap API, ID pool and bindings

On Fri, Mar 21, 2025 at 11:15:28AM +0000, Burak Emir wrote:
> This series adds a Rust bitmap API for porting the approach from 
> commit 15d9da3f818c ("binder: use bitmap for faster descriptor lookup")
> to Rust. The functionality in dbitmap.h makes use of bitmap and bitops.
> 
> The Rust bitmap API provides a safe abstraction to underlying bitmap
> and bitops operations. For now, only includes method necessary for 
> dbitmap.h, more can be added later. We perform bounds checks for 
> hardening, violations are programmer errors that result in panics.
> 
> This version includes an optimization to represent the bitmap inline,
> as suggested by Yury.

We have a tag for it:

Suggested-by: Yury Norov <yury.norov@...il.com>
 
> The Rust equivalent of dbitmap.h is included as id_pool.rs, which is
> tightly coupled to the bitmap API. Includes an example of usage
> that requires releasing a spinlock, as expected in Binder driver.

I don't think it's worth to refer the existing dbitmap.h, because:

1. It's buggy;
2. You limit yourself with committing to provide an 'equivalent' API.
3. If you want to bring the existing dbitmaps.h, you'd just bring
   bindings for them, not a re-implementation.

Can you just say that you're adding dynamic bit arrays in rust?

> This is v5 of a patch introducing Rust bitmap API [v4]. Thanks
> for all the helpful comments, this series has improved significantly
> as a result of your work.
> 
> Changes v4 --> v5: (suggested by Yury and Alice)
> - rebased on next-20250318
> - split MAINTAINERS changes
> - no dependencies on [1] and [2] anymore - Viresh,
>   please do add a separate section if you want to maintain cpumask.rs
>   separately.
> - imports atomic and non-atomic variants, introduces a naming convention
>   set_bit and set_bit_atomic on the Rust side.
> - changed naming and comments. Keeping `new`.
> - change dynamic_id_pool to id_pool
> - represent bitmap inline when possible
> - add some more tests
> - add bqe@...gle.com as M: for the Rust abstractions

Instead of 'bqe@...gle.com' just say: myself.

Thanks,
Yury