linux-kernel - Re: [PATCH v7 3/3] rust: platform: allow ioremap of platform resources

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Message-ID: <Z9qpC1EapJFNadME@pollux>
Date: Wed, 19 Mar 2025 12:22:51 +0100
From: Danilo Krummrich <dakr@...nel.org>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Daniel Almeida <daniel.almeida@...labora.com>,
	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>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v7 3/3] rust: platform: allow ioremap of platform
 resources

On Wed, Mar 19, 2025 at 12:48:00AM +0000, Benno Lossin wrote:
> On Tue Mar 18, 2025 at 7:22 PM CET, Daniel Almeida wrote:
> > On 18 Mar 2025, at 14:43, Danilo Krummrich <dakr@...nel.org> wrote:
> >> On Tue, Mar 18, 2025 at 02:20:43PM -0300, Daniel Almeida wrote:
> >>> +    ///     // Read and write a 32-bit value at `offset`. Calling `try_access()` on
> >>> +    ///     // the `Devres` makes sure that the resource is still valid.
> >>> +    ///     let data = iomem.try_access().ok_or(ENODEV)?.readl(offset);
> >>> +    ///
> >>> +    ///     iomem.try_access().ok_or(ENODEV)?.writel(data, offset);
> >> 
> >> I'd probably write this as
> >> 
> >> || -> Result {
> >> let iomem = iomem.try_access().ok_or(ENODEV)?;
> >> 
> >> iomem.read32(offset);
> >> iomem.write32(data, offset);
> >> 
> >> Ok(())
> >> }()?;
> 
> Why use a closure here?

Calling try_access() only once and not having the closure is fine too.

But I also think it would be good practice for an example to explicitly limit
the scope of the corresponding guard.

Ideally, it uses [1], once available.

[1] https://lore.kernel.org/rust-for-linux/20250313-try_with-v1-1-adcae7ed98a9@nvidia.com/