linux-kernel - Re: [PATCH v14 2/3] rust: io: mem: add a generic iomem abstraction

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Message-Id: <8A8152BD-A314-4A23-B104-AD802F7E2DB6@collabora.com>
Date: Wed, 16 Jul 2025 18:52:54 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: 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 <lossin@...nel.org>,
 Andreas Hindborg <a.hindborg@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v14 2/3] rust: io: mem: add a generic iomem abstraction

Hi,

[…]

> +
> +/// An exclusive memory-mapped IO region.
> +///
> +/// # Invariants
> +///
> +/// - [`ExclusiveIoMem`] has exclusive access to the underlying [`IoMem`].
> +pub struct ExclusiveIoMem<const SIZE: usize> {
> +    /// The underlying `IoMem` instance.
> +    iomem: IoMem<SIZE>,
> +
> +    /// The region abstraction. This represents exclusive access to the
> +    /// range represented by the underlying `iomem`.
> +    ///
> +    /// This field is needed for ownership of the region.
> +    _region: Region,
> +}
> +
> +impl<const SIZE: usize> ExclusiveIoMem<SIZE> {
> +    /// Creates a new `ExclusiveIoMem` instance.
> +    fn ioremap(resource: &Resource) -> Result<Self> {
> +        let start = resource.start();
> +        let size = resource.size();
> +        let name = resource.name().ok_or(EINVAL)?;

Note the change above. If there’s no name, we fail.

I just noticed that this may not be the right approach, but OTOH we should note that
“not having a name” is apparently considered a bug in the C code under some
circumstances:

	struct resource *r = v, *p;

        […]

	seq_printf(m, "%*s%0*llx-%0*llx : %s\n",
			depth * 2, "",
			width, start,
			width, end,
			r->name ? r->name : "<BAD>”); <—————

— Daniel