[PATCH v10 0/4] rust: platform: add Io support

[PATCH v10 0/4] rust: platform: add Io support

[Daniel Almeida]

Changes in v10:
- Rebased on driver-core-next
- Fixed examples (they were still using try_access())
- Removed map_err() from the examples, as it was not needed.
- Added a pub use for Resource in io.rs
- Reworked the platform code to make use of the pub use above
- Link to v9: https://lore.kernel.org/r/20250603-topics-tyr-platform_iomem-v9-0-a27e04157e3e@collabora.com

Changes in v9:
- Rebased on top of nova-next (for Devres::access())
- Reworked the documentation to add more markdown.
- Converted to &raw mut instead of addr_of_mut!()
- Renamed 'from_ptr' to 'as_ref' for consistency
- Changed the IoMem examples to use the signature for probe()
- Changed resource() to resource_by_index(). It's a better fit given
  the existance of resource_by_name().
- Created a separate patch for the resource accessors above.
- Moved the accessors into the generic impl block, so they work with all
  Device contexts.
- Take Device<Bound> where applicable
- Renamed "ioremap_*" to "iomap_*", in order to be consistent with the code
  in pci.rs
- Switched to Devres::access()
- Link to v8: https://lore.kernel.org/r/20250509-topics-tyr-platform_iomem-v8-0-e9f1725a40da@collabora.com

rust: platform: add Io support

Changes in v8:
- Rebased on driver-core-next
- Opted to wait for 'rust/revocable: add try_with() convenience method' to
  land instead of using the suggested closure (let me know if we should
  just switch to the closure anyways)
- Cc'd more people
- Link to v7: https://lore.kernel.org/r/20250318-topics-tyr-platform_iomem-v7-0-7438691d9ef7@collabora.com

Changes in v7:

- Rebased on top of rust-next
- Fixed a few Clippy lints
- Fixed typos (Thanks Daniel!)
- "struct Flags" now contains a usize (thanks Daniel)
- Fixed "Doc list without indentation" warning (thanks, Guangbo)

Thanks, Fiona {
- Removed RequestFn, as all functions simply used request_region and RequestFn
  had issues. Only request_region() is exposed now.
- Gated iomem_resource on CONFIG_HAS_IOMEM
- Require that the name argument be 'static
}

- Correctly check for IORESOURCE_MEM_NONPOSTED. We now call ioremap_np if that
  is set (thanks, Lina!)
- Remove #[dead_code] attribute from ExclusiveIoMem::region.

Changes in v6:

- Added Fiona as co-developer in the first patch, as I merged part of her code
from the LED driver series (thanks, Fiona)

- (Fiona) added the ResourceSize type, thereby fixing the u32 vs u64 issues
  pointed out by Christian

- Moved the request_region, release_region and friends to resource.rs

- Added the Region type. This type represents a resource returned by
  `request_region` and friends. It is also owned, representing the fact
  that the region remains marked as busy until release_region is called on
  drop. (Thanks Alice, for pointing out this pattern)

- Rewrote the IoMem abstraction to implement a separate type for exclusive
  access to an underlying region. I really disliked the `EXCLUSIVE` const
  generic, as it was definitely not ergonomic, i.e.:

  `IoMem<0, false>`

  ...doesn't really say much. In fact, I believe that boolean parameters
  hurt readability in general.

  This new approach lets users build either regular IoMem's, which basically
  call ioremap under the covers, and ExclusiveIoMem's , which also call request_region
  via the Region type.

- Added access to the ioresource_port and ioresource_mem globals.

Link to v5: https://lore.kernel.org/rust-for-linux/20250116125632.65017-1-daniel.almeida@collabora.com/

Changes in v5:

- resend v5, as the r4l list was not cc'd
- use srctree where applicable in the docs (Alice)
- Remove 'mut' in Resource::from_ptr() (Alice)
- Add 'invariants' section for Resource (Alice)
- Fix typos in mem.rs (Alice)
- Turn 'exclusive' into a const generic (Alice)
- Fix example in platform.rs (Alice)
- Rework the resource.is_null() check (Alice)
- Refactor IoMem::new() to return DevRes<IoMem> directly (Danilo)

link to v4: https://lore.kernel.org/rust-for-linux/20250109133057.243751-1-daniel.almeida@collabora.com/

Changes in v4:

- Rebased on top of driver-core-next
- Split series in multiple patches (Danilo)
- Move IoMem and Resource into its own files (Danilo)
- Fix a missing "if exclusive {...}" check (Danilo)
- Fixed the example, since it was using the old API (Danilo)
- Use Opaque in `Resource`, instead of NonNull and PhantomData (Boqun)
- Highlight that non-exclusive access to the iomem might be required in some cases
- Fixed the safety comment in IoMem::deref()

Link to v3: https://lore.kernel.org/rust-for-linux/20241211-topic-panthor-rs-platform_io_support-v3-1-08ba707e5e3b@collabora.com/

Changes in v3:
- Rebased on top of v5 for the PCI/Platform abstractions
- platform_get_resource is now called only once when calling ioremap
- Introduced a platform::Resource type, which is bound to the lifetime of the
 platform Device
- Allow retrieving resources from the platform device either by index or
 name
- Make request_mem_region() optional
- Use resource.name() in request_mem_region
- Reword the example to remove an unaligned, out-of-bounds offset
- Update the safety requirements of platform::IoMem

Changes in v2:
- reworked the commit message
- added missing request_mem_region call (Thanks Alice, Danilo)
- IoMem::new() now takes the platform::Device, the resource number and
 the name, instead of an address and a size (thanks, Danilo)
- Added a new example for both sized and unsized versions of IoMem.
- Compiled the examples using kunit.py (thanks for the tip, Alice!)
- Removed instances of `foo as _`. All `as` casts now spell out the actual
 type.
- Now compiling with CLIPPY=1 (I realized I had forgotten, sorry)
- Rebased on top of rust-next to check for any warnings given the new
 unsafe lints.

Daniel Almeida (3):
  rust: io: add resource abstraction
  rust: io: mem: add a generic iomem abstraction
  rust: platform: allow ioremap of platform resources

 rust/bindings/bindings_helper.h |   1 +
 rust/helpers/io.c               |  36 +++++
 rust/kernel/io.rs               |   3 +
 rust/kernel/io/mem.rs           | 125 ++++++++++++++++
 rust/kernel/io/resource.rs      | 252 ++++++++++++++++++++++++++++++++
 rust/kernel/platform.rs         | 123 +++++++++++++++-
 6 files changed, 539 insertions(+), 1 deletion(-)
 create mode 100644 rust/kernel/io/mem.rs
 create mode 100644 rust/kernel/io/resource.rs

--
2.48.0

---
Daniel Almeida (4):
      rust: io: add resource abstraction
      rust: io: mem: add a generic iomem abstraction
      rust: platform: add resource accessors
      rust: platform: allow ioremap of platform resources

 rust/bindings/bindings_helper.h |   1 +
 rust/helpers/io.c               |  41 ++++++++
 rust/kernel/io.rs               |   5 +
 rust/kernel/io/mem.rs           | 142 +++++++++++++++++++++++++
 rust/kernel/io/resource.rs      | 222 ++++++++++++++++++++++++++++++++++++++++
 rust/kernel/platform.rs         | 156 +++++++++++++++++++++++++++-
 6 files changed, 566 insertions(+), 1 deletion(-)
---
base-commit: 63dafeb392139b893a73b6331f347613f0929702
change-id: 20250318-topics-tyr-platform_iomem-1710a177e1df

Best regards,
-- 
Daniel Almeida <daniel.almeida@collabora.com>

[PATCH v10 1/4] rust: io: add resource abstraction

[Daniel Almeida]

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 8cbb660e2ec218021d16e6e0144acf6f4d7cca13..38992cb4b2fc33c51c6894cf2a0b8a1366c338a3 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -52,6 +52,7 @@
 #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

[PATCH v10 2/4] rust: io: mem: add a generic iomem abstraction

[Daniel Almeida]

Add a generic iomem abstraction to safely read and write ioremapped
regions.

The reads and writes are done through IoRaw, and are thus checked either
at compile-time, if the size of the region is known at that point, or at
runtime otherwise.

Non-exclusive access to the underlying memory region is made possible to
cater to cases where overlapped regions are unavoidable.

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
---
 rust/helpers/io.c     |   5 ++
 rust/kernel/io.rs     |   1 +
 rust/kernel/io/mem.rs | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 148 insertions(+)

diff --git a/rust/helpers/io.c b/rust/helpers/io.c
index 404776cf6717c8570c7600a24712ce6e4623d3c6..c475913c69e647b1042e8e7d66b9148d892947a1 100644
--- a/rust/helpers/io.c
+++ b/rust/helpers/io.c
@@ -8,6 +8,11 @@ void __iomem *rust_helper_ioremap(phys_addr_t offset, size_t size)
 	return ioremap(offset, size);
 }
 
+void __iomem *rust_helper_ioremap_np(phys_addr_t offset, size_t size)
+{
+	return ioremap_np(offset, size);
+}
+
 void rust_helper_iounmap(void __iomem *addr)
 {
 	iounmap(addr);
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 7b70d5b5477e57d6d0f24bcd26bd8b0071721bc0..b7fc759f8b5d3c3ac6f33f5a66e9f619c58b7405 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -7,6 +7,7 @@
 use crate::error::{code::EINVAL, Result};
 use crate::{bindings, build_assert};
 
+pub mod mem;
 pub mod resource;
 
 pub use resource::Resource;
diff --git a/rust/kernel/io/mem.rs b/rust/kernel/io/mem.rs
new file mode 100644
index 0000000000000000000000000000000000000000..2bd9cf4c4f1a59f027999a6e9a203dc99ad6c003
--- /dev/null
+++ b/rust/kernel/io/mem.rs
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic memory-mapped IO.
+
+use core::ops::Deref;
+
+use crate::device::Bound;
+use crate::device::Device;
+use crate::devres::Devres;
+use crate::io;
+use crate::io::resource::Region;
+use crate::io::resource::Resource;
+use crate::io::Io;
+use crate::io::IoRaw;
+use crate::prelude::*;
+
+/// An exclusive memory-mapped IO region.
+///
+/// # Invariants
+///
+/// - [`ExclusiveIoMem`] has exclusive access to the underlying [`IoMem`].
+pub struct ExclusiveIoMem<const SIZE: usize> {
+    /// The region abstraction. This represents exclusive access to the
+    /// range represented by the underlying `iomem`.
+    ///
+    /// It's placed first to ensure that the region is released before it is
+    /// unmapped as a result of the drop order.
+    ///
+    /// This field is needed for ownership of the region.
+    _region: Region,
+    /// The underlying `IoMem` instance.
+    iomem: IoMem<SIZE>,
+}
+
+impl<const SIZE: usize> ExclusiveIoMem<SIZE> {
+    /// Creates a new `ExclusiveIoMem` instance.
+    pub(crate) fn ioremap(resource: &Resource) -> Result<Self> {
+        let iomem = IoMem::ioremap(resource)?;
+
+        let start = resource.start();
+        let size = resource.size();
+        let name = resource.name();
+
+        let region = resource
+            .request_region(start, size, name, io::resource::flags::IORESOURCE_MEM)
+            .ok_or(EBUSY)?;
+
+        let iomem = ExclusiveIoMem {
+            iomem,
+            _region: region,
+        };
+
+        Ok(iomem)
+    }
+
+    pub(crate) fn new(resource: &Resource, device: &Device<Bound>) -> Result<Devres<Self>> {
+        let iomem = Self::ioremap(resource)?;
+        let devres = Devres::new(device, iomem, GFP_KERNEL)?;
+
+        Ok(devres)
+    }
+}
+
+impl<const SIZE: usize> Deref for ExclusiveIoMem<SIZE> {
+    type Target = Io<SIZE>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.iomem
+    }
+}
+
+/// A generic memory-mapped IO region.
+///
+/// Accesses to the underlying region is checked either at compile time, if the
+/// region's size is known at that point, or at runtime otherwise.
+///
+/// # Invariants
+///
+/// [`IoMem`] always holds an [`IoRaw`] instance that holds a valid pointer to the
+/// start of the I/O memory mapped region.
+pub struct IoMem<const SIZE: usize = 0> {
+    io: IoRaw<SIZE>,
+}
+
+impl<const SIZE: usize> IoMem<SIZE> {
+    fn ioremap(resource: &Resource) -> Result<Self> {
+        let size = resource.size();
+        if size == 0 {
+            return Err(EINVAL);
+        }
+
+        let res_start = resource.start();
+
+        let addr = if resource
+            .flags()
+            .contains(io::resource::flags::IORESOURCE_MEM_NONPOSTED)
+        {
+            // SAFETY:
+            // - `res_start` and `size` are read from a presumably valid `struct resource`.
+            // - `size` is known not to be zero at this point.
+            unsafe { bindings::ioremap_np(res_start, size as usize) }
+        } else {
+            // SAFETY:
+            // - `res_start` and `size` are read from a presumably valid `struct resource`.
+            // - `size` is known not to be zero at this point.
+            unsafe { bindings::ioremap(res_start, size as usize) }
+        };
+
+        if addr.is_null() {
+            return Err(ENOMEM);
+        }
+
+        let io = IoRaw::new(addr as usize, size as usize)?;
+        let io = IoMem { io };
+
+        Ok(io)
+    }
+
+    /// Creates a new `IoMem` instance.
+    pub(crate) fn new(resource: &Resource, device: &Device<Bound>) -> Result<Devres<Self>> {
+        let io = Self::ioremap(resource)?;
+        let devres = Devres::new(device, io, GFP_KERNEL)?;
+
+        Ok(devres)
+    }
+}
+
+impl<const SIZE: usize> Drop for IoMem<SIZE> {
+    fn drop(&mut self) {
+        // SAFETY: Safe as by the invariant of `Io`.
+        unsafe { bindings::iounmap(self.io.addr() as *mut core::ffi::c_void) }
+    }
+}
+
+impl<const SIZE: usize> Deref for IoMem<SIZE> {
+    type Target = Io<SIZE>;
+
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: Safe as by the invariant of `IoMem`.
+        unsafe { Io::from_raw(&self.io) }
+    }
+}

-- 
2.50.0

[PATCH v10 3/4] rust: platform: add resource accessors

[Daniel Almeida]

A previous patch has exposed the abstractions struct resource.

Now make it possible to retrieve resources from platform devices in Rust
using either a name or an index.

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
---
 rust/kernel/platform.rs | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 5b21fa517e55348582622ec10471918919502959..0eedb8239fec31df7ab64dc68d220c9d965f1f21 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -7,6 +7,7 @@
 use crate::{
     bindings, container_of, device, driver,
     error::{to_result, Result},
+    io::Resource,
     of,
     prelude::*,
     str::CStr,
@@ -188,6 +189,43 @@ impl<Ctx: device::DeviceContext> Device<Ctx> {
     fn as_raw(&self) -> *mut bindings::platform_device {
         self.0.get()
     }
+
+    /// Returns the resource at `index`, if any.
+    pub fn resource_by_index(&self, index: u32) -> Option<&Resource> {
+        // SAFETY: `self.as_raw()` returns a valid pointer to a `struct platform_device`.
+        let resource = unsafe {
+            bindings::platform_get_resource(self.as_raw(), bindings::IORESOURCE_MEM, index)
+        };
+
+        if resource.is_null() {
+            return None;
+        }
+
+        // SAFETY: `resource` is a valid pointer to a `struct resource` as
+        // returned by `platform_get_resource`.
+        Some(unsafe { Resource::as_ref(resource) })
+    }
+
+    /// Returns the resource with a given `name`, if any.
+    pub fn resource_by_name(&self, name: &CStr) -> Option<&Resource> {
+        // SAFETY: `self.as_raw()` returns a valid pointer to a `struct
+        // platform_device` and `name` points to a valid C string.
+        let resource = unsafe {
+            bindings::platform_get_resource_byname(
+                self.as_raw(),
+                bindings::IORESOURCE_MEM,
+                name.as_char_ptr(),
+            )
+        };
+
+        if resource.is_null() {
+            return None;
+        }
+
+        // SAFETY: `resource` is a valid pointer to a `struct resource` as
+        // returned by `platform_get_resource`.
+        Some(unsafe { Resource::as_ref(resource) })
+    }
 }
 
 // SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic

-- 
2.50.0

[PATCH v10 4/4] rust: platform: allow ioremap of platform resources

[Daniel Almeida]

The preceding patches added support for resources, and for a general
IoMem abstraction, but thus far there is no way to access said IoMem
from drivers, as its creation is unsafe and depends on a resource that
must be acquired from some device first.

Now, allow the ioremap of platform resources themselves, thereby making
the IoMem available to platform drivers.

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
---
 rust/kernel/platform.rs | 120 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 118 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 0eedb8239fec31df7ab64dc68d220c9d965f1f21..5e787cf85f41722837bb34a6620c92d13d55625b 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -5,9 +5,14 @@
 //! C header: [`include/linux/platform_device.h`](srctree/include/linux/platform_device.h)
 
 use crate::{
-    bindings, container_of, device, driver,
+    bindings, container_of, device,
+    devres::Devres,
+    driver,
     error::{to_result, Result},
-    io::Resource,
+    io::{
+        mem::{ExclusiveIoMem, IoMem},
+        Resource,
+    },
     of,
     prelude::*,
     str::CStr,
@@ -228,6 +233,117 @@ pub fn resource_by_name(&self, name: &CStr) -> Option<&Resource> {
     }
 }
 
+impl Device<device::Bound> {
+    /// Maps a platform resource where the size is known at compile time.
+    ///
+    /// This uses the
+    /// [`ioremap()`](https://docs.kernel.org/driver-api/device-io.html#getting-access-to-the-device)
+    /// C API.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # use kernel::{bindings, c_str, platform, of, device::Core};
+    /// # struct SampleDriver;
+    ///
+    /// impl platform::Driver for SampleDriver {
+    ///    # type IdInfo = ();
+    ///    # const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = None;
+    ///
+    ///    fn probe(
+    ///       pdev: &platform::Device<Core>,
+    ///       info: Option<&Self::IdInfo>,
+    ///    ) -> Result<Pin<KBox<Self>>> {
+    ///       let offset = 0; // Some offset.
+    ///
+    ///       // If the size is known at compile time, use [`Self::iomap_resource_sized`].
+    ///       //
+    ///       // No runtime checks will apply when reading and writing.
+    ///       let resource = pdev.resource_by_index(0).ok_or(ENODEV)?;
+    ///       let iomem = pdev.iomap_resource_sized::<42>(&resource)?;
+    ///       let io = iomem.access(pdev.as_ref())?;
+    ///
+    ///       // Read and write a 32-bit value at `offset`.
+    ///       let data = io.read32_relaxed(offset);
+    ///
+    ///       io.write32_relaxed(data, offset);
+    ///
+    ///       # Ok(KBox::new(SampleDriver, GFP_KERNEL)?.into())
+    ///     }
+    /// }
+    /// ```
+    pub fn iomap_resource_sized<const SIZE: usize>(
+        &self,
+        resource: &Resource,
+    ) -> Result<Devres<IoMem<SIZE>>> {
+        IoMem::new(resource, self.as_ref())
+    }
+
+    /// Same as [`Self::iomap_resource_sized`] but with exclusive access to the
+    /// underlying region.
+    ///
+    /// This uses the
+    /// [`ioremap()`](https://docs.kernel.org/driver-api/device-io.html#getting-access-to-the-device)
+    /// C API.
+    pub fn iomap_resource_exclusive_sized<const SIZE: usize>(
+        &self,
+        resource: &Resource,
+    ) -> Result<Devres<ExclusiveIoMem<SIZE>>> {
+        ExclusiveIoMem::new(resource, self.as_ref())
+    }
+
+    /// Maps a platform resource through `iomap()`.
+    ///
+    /// This uses the
+    /// [`ioremap()`](https://docs.kernel.org/driver-api/device-io.html#getting-access-to-the-device)
+    /// C API.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # use kernel::{bindings, c_str, platform, of, device::Core};
+    /// # struct SampleDriver;
+    ///
+    /// impl platform::Driver for SampleDriver {
+    ///    # type IdInfo = ();
+    ///    # const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = None;
+    ///
+    ///    fn probe(
+    ///       pdev: &platform::Device<Core>,
+    ///       info: Option<&Self::IdInfo>,
+    ///    ) -> Result<Pin<KBox<Self>>> {
+    ///       let offset = 0; // Some offset.
+    ///
+    ///       // Unlike [`Self::iomap_resource_sized`], here the size of the memory region
+    ///       // is not known at compile time, so only the `try_read*` and `try_write*`
+    ///       // family of functions should be used, leading to runtime checks on every
+    ///       // access.
+    ///       let resource = pdev.resource_by_index(0).ok_or(ENODEV)?;
+    ///       let iomem = pdev.iomap_resource(&resource)?;
+    ///       let io = iomem.access(pdev.as_ref())?;
+    ///
+    ///       let data = io.try_read32_relaxed(offset)?;
+    ///
+    ///       io.try_write32_relaxed(data, offset)?;
+    ///
+    ///       # Ok(KBox::new(SampleDriver, GFP_KERNEL)?.into())
+    ///     }
+    /// }
+    /// ```
+    pub fn iomap_resource(&self, resource: &Resource) -> Result<Devres<IoMem<0>>> {
+        self.iomap_resource_sized::<0>(resource)
+    }
+
+    /// Same as [`Self::iomap_resource`] but with exclusive access to the underlying
+    /// region.
+    pub fn iomap_resource_exclusive(
+        &self,
+        resource: &Resource,
+    ) -> Result<Devres<ExclusiveIoMem<0>>> {
+        self.iomap_resource_exclusive_sized::<0>(resource)
+    }
+}
+
 // SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
 // argument.
 kernel::impl_device_context_deref!(unsafe { Device });

-- 
2.50.0

Re: [PATCH v10 2/4] rust: io: mem: add a generic iomem abstraction

[Danilo Krummrich]

On Mon, Jun 23, 2025 at 03:00:59PM -0300, Daniel Almeida wrote:
> Add a generic iomem abstraction to safely read and write ioremapped
> regions.
> 
> The reads and writes are done through IoRaw, and are thus checked either
> at compile-time, if the size of the region is known at that point, or at
> runtime otherwise.
> 
> Non-exclusive access to the underlying memory region is made possible to
> cater to cases where overlapped regions are unavoidable.
> 
> Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
> ---
>  rust/helpers/io.c     |   5 ++
>  rust/kernel/io.rs     |   1 +
>  rust/kernel/io/mem.rs | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 148 insertions(+)
> 
> diff --git a/rust/helpers/io.c b/rust/helpers/io.c
> index 404776cf6717c8570c7600a24712ce6e4623d3c6..c475913c69e647b1042e8e7d66b9148d892947a1 100644
> --- a/rust/helpers/io.c
> +++ b/rust/helpers/io.c
> @@ -8,6 +8,11 @@ void __iomem *rust_helper_ioremap(phys_addr_t offset, size_t size)
>  	return ioremap(offset, size);
>  }
>  
> +void __iomem *rust_helper_ioremap_np(phys_addr_t offset, size_t size)
> +{
> +	return ioremap_np(offset, size);
> +}
> +
>  void rust_helper_iounmap(void __iomem *addr)
>  {
>  	iounmap(addr);
> diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
> index 7b70d5b5477e57d6d0f24bcd26bd8b0071721bc0..b7fc759f8b5d3c3ac6f33f5a66e9f619c58b7405 100644
> --- a/rust/kernel/io.rs
> +++ b/rust/kernel/io.rs
> @@ -7,6 +7,7 @@
>  use crate::error::{code::EINVAL, Result};
>  use crate::{bindings, build_assert};
>  
> +pub mod mem;
>  pub mod resource;
>  
>  pub use resource::Resource;
> diff --git a/rust/kernel/io/mem.rs b/rust/kernel/io/mem.rs
> new file mode 100644
> index 0000000000000000000000000000000000000000..2bd9cf4c4f1a59f027999a6e9a203dc99ad6c003
> --- /dev/null
> +++ b/rust/kernel/io/mem.rs
> @@ -0,0 +1,142 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Generic memory-mapped IO.
> +
> +use core::ops::Deref;
> +
> +use crate::device::Bound;
> +use crate::device::Device;
> +use crate::devres::Devres;
> +use crate::io;
> +use crate::io::resource::Region;
> +use crate::io::resource::Resource;
> +use crate::io::Io;
> +use crate::io::IoRaw;
> +use crate::prelude::*;
> +
> +/// An exclusive memory-mapped IO region.
> +///
> +/// # Invariants
> +///
> +/// - [`ExclusiveIoMem`] has exclusive access to the underlying [`IoMem`].
> +pub struct ExclusiveIoMem<const SIZE: usize> {
> +    /// The region abstraction. This represents exclusive access to the
> +    /// range represented by the underlying `iomem`.
> +    ///
> +    /// It's placed first to ensure that the region is released before it is
> +    /// unmapped as a result of the drop order.

Isn't it more logical the other way around, i.e. first free the resource and
then release the resource guard?

Anyways, I don't think it matters too much, since drop() owns the object and
Devres guarantees that we can't race with another device trying to access the
resource.

Otherwise, I guess you could drop() the object and create a new one right away,
but that doesn't seem to be a problem either for any order?

> +    /// This field is needed for ownership of the region.
> +    _region: Region,
> +    /// The underlying `IoMem` instance.
> +    iomem: IoMem<SIZE>,
> +}
> +
> +impl<const SIZE: usize> ExclusiveIoMem<SIZE> {
> +    /// Creates a new `ExclusiveIoMem` instance.
> +    pub(crate) fn ioremap(resource: &Resource) -> Result<Self> {
> +        let iomem = IoMem::ioremap(resource)?;
> +
> +        let start = resource.start();
> +        let size = resource.size();
> +        let name = resource.name();
> +
> +        let region = resource
> +            .request_region(start, size, name, io::resource::flags::IORESOURCE_MEM)
> +            .ok_or(EBUSY)?;

Same here, why do the ioremap() first? I think it logically makes more sense to
first try and get the region.