[PATCH v7 1/3] rust: io: add resource abstraction

Daniel Almeida
2025-03-18T17:21:25Z

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.

Co-developed-by: Fiona Behrens <me@kloenk.dev>
Signed-off-by: Fiona Behrens <me@kloenk.dev>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
---
rust/bindings/bindings_helper.h | 1 +
rust/helpers/io.c | 36 +++++++
rust/kernel/io.rs | 2 +
rust/kernel/io/resource.rs | 222 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 261 insertions(+)

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index ae39fc18a8bf07be385e383e5ee0a2e30c6922b4..89a2a17841b55b31afd385bda3566a8eb08b4f7e 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -17,6 +17,7 @@
#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 4c2401ccd72078af4e6901f4cd95f9070522f396..939ab38ca61dac4cf884677a20edc760094d5812 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 +100,38 @@ 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);
+}
+
+struct resource *rust_helper_request_mem_region(resource_size_t start,
+ resource_size_t n,
+ const char *name)
+{
+ return request_mem_region(start, n, name);
+}
+
+void rust_helper_release_mem_region(resource_size_t start, resource_size_t n)
+{
+ release_mem_region(start, n);
+}
+
+struct resource *rust_helper_request_region(resource_size_t start,
+ resource_size_t n, const char *name)
+{
+ return request_region(start, n, name);
+}
+
+struct resource *rust_helper_request_muxed_region(resource_size_t start,
+ resource_size_t n,
+ const char *name)
+{
+ return request_muxed_region(start, n, name);
+}
+
+void rust_helper_release_region(resource_size_t start, resource_size_t n)
+{
+ release_region(start, n);
+}
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index d4a73e52e3ee68f7b558749ed0108acde92ae5fe..566d8b177e01ada5b184d4250dc24caba6492e49 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 0000000000000000000000000000000000000000..3eb5c8ef585078398551fe8189fd96c1b6c1eeff
--- /dev/null
+++ b/rust/kernel/io/resource.rs
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Abstraction for system resources.
+//!
+//! C header: [`include/linux/ioport.h`](srctree/include/linux/ioport.h)
+
+use core::ops::Deref;
+use core::ptr::NonNull;
+
+use crate::str::CStr;
+use crate::types::Opaque;
+
+#[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)) }
+}
+
+#[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)) }
+}
+
+/// Resource Size type.
+///
+/// This is a type alias to `u64` depending on the config option
+/// `CONFIG_PHYS_ADDR_T_64BIT`.
+#[cfg(CONFIG_PHYS_ADDR_T_64BIT)]
+pub type ResourceSize = u64;
+
+/// Resource Size type.
+///
+/// This is a type alias to `u32` depending on the config option
+/// `CONFIG_PHYS_ADDR_T_64BIT`.
+#[cfg(not(CONFIG_PHYS_ADDR_T_64BIT))]
+pub type ResourceSize = u32;
+
+/// A region allocated from a parent resource.
+///
+/// # Invariants
+///
+/// - `self.0` points to a valid `bindings::resource` that was obtained through
+/// `__request_region`.
+pub struct Region(NonNull<bindings::resource>);
+
+impl Deref for Region {
+ type Target = Resource;
+
+ fn deref(&self) -> &Self::Target {
+ // SAFETY: Safe as per the invariant of `Region`
+ unsafe { Resource::from_ptr(self.0.as_ptr()) }
+ }
+}
+
+impl Drop for Region {
+ fn drop(&mut self) {
+ // SAFETY: Safe as per the invariant of `Region`
+ let res = unsafe { Resource::from_ptr(self.0.as_ptr()) };
+ let flags = res.flags();
+
+ let release_fn = if flags.contains(flags::IORESOURCE_MEM) {
+ bindings::release_mem_region
+ } else {
+ bindings::release_region
+ };
+
+ // SAFETY: Safe as per the invariant of `Region`
+ unsafe { release_fn(res.start(), res.size()) };
+ }
+}
+
+// SAFETY: `Region` only holds a pointer to a C `struct resource`, which is safe to be used from
+// any thread.
+unsafe impl Send for Region {}
+
+// SAFETY: `Region` only holds a pointer to a C `struct resource`, references to which are
+// safe to be used from any thread.
+unsafe impl Sync for Region {}
+
+/// 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 {
+ // SAFETY: Self is a transparent wrapper around `Opaque<bindings::resource>`.
+ unsafe { &*ptr.cast() }
+ }
+
+ /// Requests a resource region.
+ ///
+ /// Exclusive access will be given and the region will be marked as busy.
+ /// Further calls to `request_region` will return `None` if the region, or a
+ /// part of it, is already in use.
+ pub fn request_region(
+ &self,
+ start: ResourceSize,
+ size: ResourceSize,
+ name: &'static CStr,
+ flags: Flags,
+ ) -> Option<Region> {
+ // SAFETY: Safe as per the invariant of `Resource`
+ let region = unsafe {
+ bindings::__request_region(
+ self.0.get(),
+ start,
+ size,
+ name.as_char_ptr(),
+ flags.0 as i32,
+ )
+ };
+
+ Some(Region(NonNull::new(region)?))
+ }
+
+ /// Returns the size of the resource.
+ pub fn size(&self) -> ResourceSize {
+ 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 {
+ 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) -> &'static CStr {
+ let inner = self.0.get();
+ // SAFETY: safe as per the invariants of `Resource`
+ unsafe { CStr::from_char_ptr((*inner).name) }
+ }
+
+ /// Returns the flags associated with the resource.
+ pub fn flags(&self) -> Flags {
+ let inner = self.0.get();
+ // SAFETY: safe as per the invariants of `Resource`
+ let flags = unsafe { *inner }.flags;
+
+ Flags(flags)
+ }
+}
+
+// SAFETY: `Resource` only holds a pointer to a C `struct resource`, which is safe to be used from
+// any thead.
+unsafe impl Send for Resource {}
+
+// SAFETY: `Resource` only holds a pointer to a C `struct resource`, references to which are
+// safe to be used from any thead.
+unsafe impl Sync for Resource {}
+
+/// Resource flags as stored in the C `struct resource::flags` field.
+///
+/// They can be combined with the operators `|`, `&`, and `!`.
+///
+/// Values can be used from the [`flags`] module.
+#[derive(Clone, Copy, PartialEq)]
+pub struct Flags(usize);
+
+impl Flags {
+ /// Check whether `flags` is contained in `self`.
+ pub fn contains(self, flags: Flags) -> bool {
+ (self & flags) == flags
+ }
+}
+
+impl core::ops::BitOr for Flags {
+ type Output = Self;
+ fn bitor(self, rhs: Self) -> Self::Output {
+ Self(self.0 | rhs.0)
+ }
+}
+
+impl core::ops::BitAnd for Flags {
+ type Output = Self;
+ fn bitand(self, rhs: Self) -> Self::Output {
+ Self(self.0 & rhs.0)
+ }
+}
+
+impl core::ops::Not for Flags {
+ type Output = Self;
+ fn not(self) -> Self::Output {
+ Self(!self.0)
+ }
+}
+
+/// Resource flags as stored in the `struct resource::flags` field.
+pub mod flags {
+ use super::Flags;
+
+ /// PCI/ISA I/O ports.
+ pub const IORESOURCE_IO: Flags = Flags(bindings::IORESOURCE_IO as usize);
+
+ /// Resource is software muxed.
+ pub const IORESOURCE_MUXED: Flags = Flags(bindings::IORESOURCE_MUXED as usize);
+
+ /// Resource represents a memory region.
+ pub const IORESOURCE_MEM: Flags = Flags(bindings::IORESOURCE_MEM as usize);
+
+ /// Resource represents a memory region that must be ioremaped using `ioremap_np`.
+ pub const IORESOURCE_MEM_NONPOSTED: Flags = Flags(bindings::IORESOURCE_MEM_NONPOSTED as usize);
+}

--
2.48.1