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 | 4 +
rust/kernel/io/resource.rs | 222 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 263 insertions(+)
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 7e8f2285064797d5bbac5583990ff823b76c6bdc..5f795e60e889b9fc887013743c81b1cf92a52adb 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -53,6 +53,7 @@
#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 15ea187c5466256effd07efe6f6995a1dd95a967..404776cf6717c8570c7600a24712ce6e4623d3c6 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, 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 72d80a6f131e3e826ecd9d2c3bcf54e89aa60cc3..7b70d5b5477e57d6d0f24bcd26bd8b0071721bc0 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -7,6 +7,10 @@
use crate::error::{code::EINVAL, Result};
use crate::{bindings, build_assert};
+pub mod resource;
+
+pub use resource::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..611eca8cc693d83bccc2c384db2ff22d11e7ac46
--- /dev/null
+++ b/rust/kernel/io/resource.rs
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Abstractions 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::as_ref(&raw 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::as_ref(&raw 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
+/// `bindings::__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::as_ref(self.0.as_ptr()) }
+ }
+}
+
+impl Drop for Region {
+ fn drop(&mut self) {
+ // SAFETY: Safe as per the invariant of `Region`
+ let res = unsafe { Resource::as_ref(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 as_ref<'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 [`Self::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);
+}
--
2.50.0> +#[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::as_ref(&raw 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::as_ref(&raw mut bindings::iomem_resource) }
> +}
This caught my attention, and I have a few questions:
1) What do you need them for? I don't see any methods that would usually
consume those.
2) Why are they behind CONFIG_HAS_IOPORT and CONFIG_HAS_IOMEM, even though the
C instances are not?
3) What happens if we pass them to IoMem::new()? Is this really safe, or do we
need them to be a special Resource type?
Hi Danilo
> On 2 Jul 2025, at 07:21, Danilo Krummrich <dakr@kernel.org> 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::as_ref(&raw 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::as_ref(&raw mut bindings::iomem_resource) }
>> +}
>
> This caught my attention, and I have a few questions:
>
> 1) What do you need them for? I don't see any methods that would usually
> consume those.
>
> 2) Why are they behind CONFIG_HAS_IOPORT and CONFIG_HAS_IOMEM, even though the
> C instances are not?
>
> 3) What happens if we pass them to IoMem::new()? Is this really safe, or do we
> need them to be a special Resource type?
>
Good catch, actually.
I worked on this patch with Fiona and IIRC, she needed access to these two for
her LED abstractions. This patch has seen a few iterations already and this may
or may not be obsolete by now. I must say I've never used these before so I
don't really know how they work nor do I need this at all.
Fiona, do you still need these two accessors?
— Daniel
On Wed, Jul 02, 2025 at 03:11:04PM -0300, Daniel Almeida wrote:
> Hi Danilo
>
> > On 2 Jul 2025, at 07:21, Danilo Krummrich <dakr@kernel.org> 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::as_ref(&raw 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::as_ref(&raw mut bindings::iomem_resource) }
> >> +}
> >
> > This caught my attention, and I have a few questions:
> >
> > 1) What do you need them for? I don't see any methods that would usually
> > consume those.
> >
> > 2) Why are they behind CONFIG_HAS_IOPORT and CONFIG_HAS_IOMEM, even though the
> > C instances are not?
> >
> > 3) What happens if we pass them to IoMem::new()? Is this really safe, or do we
> > need them to be a special Resource type?
> >
>
> Good catch, actually.
>
> I worked on this patch with Fiona and IIRC, she needed access to these two for
> her LED abstractions. This patch has seen a few iterations already and this may
> or may not be obsolete by now. I must say I've never used these before so I
> don't really know how they work nor do I need this at all.
They serve as parent / root resource instances, e.g. if you want to create new
resource regions yourself.
> Fiona, do you still need these two accessors?
I'd say let's drop them for now, we can easily add them later on in the context
of an actual user.
Hi Daniel,
A couple nits Danilo can take care of them on apply.
On Tue, Jul 1, 2025 at 4:35 PM Daniel Almeida
<daniel.almeida@collabora.com> wrote:
>
> +//! Abstractions for system resources.
Potential link:
https://docs.kernel.org/core-api/kernel-api.html#resources-management
I think there are a couple kernel-doc includes missing in the `.rst`
for this, so it is not great.
> +/// This is a type alias to `u64` depending on the config option
"to `u32` or `u64`"? (also below)
> + /// The caller must ensure that for the duration of 'a, the pointer will
`'a` (same below).
> + // SAFETY: Safe as per the invariant of `Resource`
"Safe", periods at the end. (few instances)
The last patch on the series has nice examples, thanks! It could be
nice to have some here too (e.g. on how `Flags` and its operators) and
nowadays also KUnit tests, but that can be a good first issue for
later.
Cheers,
Miguel
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