Re: [PATCH RESEND v5 1/3] rust: io: add resource abstraction

Christian Schrefl
2025-01-16T21:14:35Z

Hi Daniel

On 16.01.25 1:56 PM, Daniel Almeida wrote:
> In preparation for ioremap support, add a Rust abstraction for struct
> resource.
>
> A future commit will introduce the Rust API to ioremap a resource from a
> platform device. The current abstraction, therefore, adds only the
> minimum API needed to get that done.
>
> Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
> ---
> rust/bindings/bindings_helper.h | 1 +
> rust/helpers/io.c | 7 +++++
> rust/kernel/io.rs | 2 ++
> rust/kernel/io/resource.rs | 53 +++++++++++++++++++++++++++++++++
> 4 files changed, 63 insertions(+)
> create mode 100644 rust/kernel/io/resource.rs
>
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index e9fdceb568b8..f9c2eedb5b9b 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -16,6 +16,7 @@
> #include <linux/file.h>
> #include <linux/firmware.h>
> #include <linux/fs.h>
> +#include <linux/ioport.h>
> #include <linux/jiffies.h>
> #include <linux/jump_label.h>
> #include <linux/mdio.h>
> diff --git a/rust/helpers/io.c b/rust/helpers/io.c
> index 4c2401ccd720..3cb47bd01942 100644
> --- a/rust/helpers/io.c
> +++ b/rust/helpers/io.c
> @@ -1,6 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0
>
> #include <linux/io.h>
> +#include <linux/ioport.h>
>
> void __iomem *rust_helper_ioremap(phys_addr_t offset, size_t size)
> {
> @@ -99,3 +100,9 @@ void rust_helper_writeq_relaxed(u64 value, volatile void __iomem *addr)
> writeq_relaxed(value, addr);
> }
> #endif
> +
> +resource_size_t rust_helper_resource_size(struct resource *res)
> +{
> + return resource_size(res);
> +}
> +
> diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
> index d4a73e52e3ee..566d8b177e01 100644
> --- a/rust/kernel/io.rs
> +++ b/rust/kernel/io.rs
> @@ -7,6 +7,8 @@
> use crate::error::{code::EINVAL, Result};
> use crate::{bindings, build_assert};
>
> +pub mod resource;
> +
> /// Raw representation of an MMIO region.
> ///
> /// By itself, the existence of an instance of this structure does not provide any guarantees that
> diff --git a/rust/kernel/io/resource.rs b/rust/kernel/io/resource.rs
> new file mode 100644
> index 000000000000..ca92f9af613b
> --- /dev/null
> +++ b/rust/kernel/io/resource.rs
> @@ -0,0 +1,53 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Abstraction for system resources.
> +//!
> +//! C header: [`include/linux/ioport.h`](srctree/include/linux/ioport.h)
> +
> +use crate::str::CStr;
> +use crate::types::Opaque;
> +
> +/// 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) unsafe fn from_ptr<'a>(ptr: *mut bindings::resource) -> &'a Self {
> + // SAFETY: Self is a transparent wrapper around `Opaque<bindings::resource>`.
> + unsafe { &*ptr.cast() }
> + }
> +
> + /// Returns the size of the resource.
> + pub fn size(&self) -> bindings::resource_size_t {
> + let inner = self.0.get();
> + // SAFETY: safe as per the invariants of `Resource`
> + unsafe { bindings::resource_size(inner) }
> + }
> +
> + /// Returns the start address of the resource.
> + pub fn start(&self) -> u64 {

Please use bindings::resource_size_t to be compatible with 32-bit architectures.

> + let inner = self.0.get();
> + // SAFETY: safe as per the invariants of `Resource`
> + unsafe { *inner }.start
> + }
> +
> + /// Returns the name of the resource.
> + pub fn name(&self) -> &CStr {
> + let inner = self.0.get();
> + // SAFETY: safe as per the invariants of `Resource`
> + unsafe { CStr::from_char_ptr((*inner).name) }
> + }
> +}

Cheers
Christian