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Date: Thu, 15 May 2025 17:53:57 +0200
From: Danilo Krummrich <dakr@kernel.org>
To: Daniel Almeida <daniel.almeida@collabora.com>
Cc: Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@gmail.com>,
	Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <benno.lossin@proton.me>,
	Andreas Hindborg <a.hindborg@kernel.org>,
	Alice Ryhl <aliceryhl@google.com>, Trevor Gross <tmgross@umich.edu>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Ilpo =?iso-8859-1?Q?J=E4rvinen?= <ilpo.jarvinen@linux.intel.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Ying Huang <huang.ying.caritas@gmail.com>,
	linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
	Fiona Behrens <me@kloenk.dev>
Subject: Re: [PATCH v8 1/3] rust: io: add resource abstraction
Message-ID: <aCYOFbVn8LcOpWPf@pollux>
References: <20250509-topics-tyr-platform_iomem-v8-0-e9f1725a40da@collabora.com>
 <20250509-topics-tyr-platform_iomem-v8-1-e9f1725a40da@collabora.com>
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In-Reply-To: <20250509-topics-tyr-platform_iomem-v8-1-e9f1725a40da@collabora.com>

On Fri, May 09, 2025 at 05:29:46PM -0300, Daniel Almeida wrote:
> +#[cfg(CONFIG_HAS_IOPORT)]
> +/// Returns a reference to the global `ioport_resource` variable.
> +pub fn ioport_resource() -> &'static Resource {
> +    // SAFETY: `bindings::ioport_resoure` has global lifetime and is of type Resource.
> +    unsafe { Resource::from_ptr(core::ptr::addr_of_mut!(bindings::ioport_resource)) }

Should be possible to use `&raw mut`.

> +}
> +
> +#[cfg(CONFIG_HAS_IOMEM)]
> +/// Returns a reference to the global `iomem_resource` variable.
> +pub fn iomem_resource() -> &'static Resource {
> +    // SAFETY: `bindings::iomem_resoure` has global lifetime and is of type Resource.
> +    unsafe { Resource::from_ptr(core::ptr::addr_of_mut!(bindings::iomem_resource)) }

Same here.

> +/// A resource abstraction.
> +///
> +/// # Invariants
> +///
> +/// `Resource` is a transparent wrapper around a valid `bindings::resource`.
> +#[repr(transparent)]
> +pub struct Resource(Opaque<bindings::resource>);
> +
> +impl Resource {
> +    /// Creates a reference to a [`Resource`] from a valid pointer.
> +    ///
> +    /// # Safety
> +    ///
> +    /// The caller must ensure that for the duration of 'a, the pointer will
> +    /// point at a valid `bindings::resource`
> +    ///
> +    /// The caller must also ensure that the `Resource` is only accessed via the
> +    /// returned reference for the duration of 'a.
> +    pub(crate) const unsafe fn from_ptr<'a>(ptr: *mut bindings::resource) -> &'a Self {

Throughout the tree, functions with this signature are usually called as_ref().