[PATCH RESEND v5 0/3] rust: platform: add Io support

[PATCH RESEND v5 0/3] rust: platform: add Io support

[Daniel Almeida]

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               |  17 ++++++
 rust/kernel/io.rs               |   3 +
 rust/kernel/io/mem.rs           |  98 +++++++++++++++++++++++++++++
 rust/kernel/io/resource.rs      |  53 ++++++++++++++++
 rust/kernel/platform.rs         | 105 +++++++++++++++++++++++++++++++-
 6 files changed, 276 insertions(+), 1 deletion(-)
 create mode 100644 rust/kernel/io/mem.rs
 create mode 100644 rust/kernel/io/resource.rs

-- 
2.48.0

[PATCH RESEND v5 1/3] 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.

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 {
+        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) }
+    }
+}
-- 
2.48.0

[PATCH RESEND v5 2/3] 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     | 10 +++++
 rust/kernel/io.rs     |  1 +
 rust/kernel/io/mem.rs | 98 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 109 insertions(+)
 create mode 100644 rust/kernel/io/mem.rs

diff --git a/rust/helpers/io.c b/rust/helpers/io.c
index 3cb47bd01942..cb10060c08ae 100644
--- a/rust/helpers/io.c
+++ b/rust/helpers/io.c
@@ -106,3 +106,13 @@ 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);
+}
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 566d8b177e01..9ce3482b5ecd 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;
 
 /// Raw representation of an MMIO region.
diff --git a/rust/kernel/io/mem.rs b/rust/kernel/io/mem.rs
new file mode 100644
index 000000000000..a287dc0898e0
--- /dev/null
+++ b/rust/kernel/io/mem.rs
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic memory-mapped IO.
+
+use core::ops::Deref;
+
+use crate::device::Device;
+use crate::devres::Devres;
+use crate::io::resource::Resource;
+use crate::io::Io;
+use crate::io::IoRaw;
+use crate::prelude::*;
+
+/// 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.
+///
+/// Whether `IoMem` represents an exclusive access to the underlying memory
+/// region is determined by the caller at creation time, as overlapping access
+/// may be needed in some cases.
+///
+/// # Invariants
+///
+/// `IoMem` always holds an `IoRaw` inststance that holds a valid pointer to the
+/// start of the I/O memory mapped region.
+pub struct IoMem<const SIZE: usize = 0, const EXCLUSIVE: bool = true> {
+    io: IoRaw<SIZE>,
+    res_start: u64,
+}
+
+impl<const SIZE: usize, const EXCLUSIVE: bool> IoMem<SIZE, EXCLUSIVE> {
+    /// Creates a new `IoMem` instance.
+    pub(crate) fn new(resource: &Resource, device: &Device) -> Result<Devres<Self>> {
+        let size = resource.size();
+        if size == 0 {
+            return Err(EINVAL);
+        }
+
+        let res_start = resource.start();
+
+        if EXCLUSIVE {
+            // SAFETY:
+            // - `res_start` and `size` are read from a presumably valid `struct resource`.
+            // - `size` is known not to be zero at this point.
+            // - `resource.name()` returns a valid C string.
+            let mem_region = unsafe {
+                bindings::request_mem_region(res_start, size, resource.name().as_char_ptr())
+            };
+
+            if mem_region.is_null() {
+                return Err(EBUSY);
+            }
+        }
+
+        // SAFETY:
+        // - `res_start` and `size` are read from a presumably valid `struct resource`.
+        // - `size` is known not to be zero at this point.
+        let addr = unsafe { bindings::ioremap(res_start, size as kernel::ffi::c_ulong) };
+        if addr.is_null() {
+            if EXCLUSIVE {
+                // SAFETY:
+                // - `res_start` and `size` are read from a presumably valid `struct resource`.
+                // - `size` is the same as the one passed to `request_mem_region`.
+                unsafe { bindings::release_mem_region(res_start, size) };
+            }
+            return Err(ENOMEM);
+        }
+
+        let io = IoRaw::new(addr as usize, size as usize)?;
+        let io = IoMem { io, res_start };
+        let devres = Devres::new(device, io, GFP_KERNEL)?;
+
+        Ok(devres)
+    }
+}
+
+impl<const SIZE: usize, const EXCLUSIVE: bool> Drop for IoMem<SIZE, EXCLUSIVE> {
+    fn drop(&mut self) {
+        if EXCLUSIVE {
+            // SAFETY: `res_start` and `io.maxsize()` were the values passed to
+            // `request_mem_region`.
+            unsafe { bindings::release_mem_region(self.res_start, self.io.maxsize() as u64) }
+        }
+
+        // SAFETY: Safe as by the invariant of `Io`.
+        unsafe { bindings::iounmap(self.io.addr() as *mut core::ffi::c_void) }
+    }
+}
+
+impl<const SIZE: usize, const EXCLUSIVE: bool> Deref for IoMem<SIZE, EXCLUSIVE> {
+    type Target = Io<SIZE>;
+
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: Safe as by the invariant of `IoMem`.
+        unsafe { Io::from_raw(&self.io) }
+    }
+}
-- 
2.48.0

[PATCH RESEND v5 3/3] 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 | 105 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 104 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 50e6b0421813..55c2e0ffd4d1 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -5,8 +5,11 @@
 //! 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::{mem::IoMem, resource::Resource},
     of,
     prelude::*,
     str::CStr,
@@ -191,6 +194,106 @@ fn as_raw(&self) -> *mut bindings::platform_device {
         // embedded in `struct platform_device`.
         unsafe { container_of!(self.0.as_raw(), bindings::platform_device, dev) }.cast_mut()
     }
+
+    /// Maps a platform resource through ioremap() where the size is known at
+    /// compile time.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use kernel::{bindings, c_str, platform};
+    ///
+    /// fn probe(pdev: &mut platform::Device, /* ... */) -> Result<()> {
+    ///     let offset = 0; // Some offset.
+    ///
+    ///     // If the size is known at compile time, use `ioremap_resource_sized`.
+    ///     // No runtime checks will apply when reading and writing.
+    ///     let resource = pdev.resource(0).ok_or(ENODEV)?;
+    ///     let iomem = pdev.ioremap_resource_sized::<42, true>(&resource)?;
+    ///
+    ///     // Read and write a 32-bit value at `offset`. Calling `try_access()` on
+    ///     // the `Devres` makes sure that the resource is still valid.
+    ///     let data = iomem.try_access().ok_or(ENODEV)?.readl(offset);
+    ///
+    ///     iomem.try_access().ok_or(ENODEV)?.writel(data, offset);
+    ///
+    ///     # Ok::<(), Error>(())
+    /// }
+    /// ```
+    pub fn ioremap_resource_sized<const SIZE: usize, const EXCLUSIVE: bool>(
+        &self,
+        resource: &Resource,
+    ) -> Result<Devres<IoMem<SIZE, EXCLUSIVE>>> {
+        IoMem::new(resource, self.as_ref())
+    }
+
+    /// Maps a platform resource through ioremap().
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # use kernel::{bindings, c_str, platform};
+    ///
+    /// fn probe(pdev: &mut platform::Device, /* ... */) -> Result<()> {
+    ///     let offset = 0; // Some offset.
+    ///
+    ///     // Unlike `ioremap_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 are exposed, leading to runtime checks on every
+    ///     // access.
+    ///     let resource = pdev.resource(0).ok_or(ENODEV)?;
+    ///     let iomem = pdev.ioremap_resource::<true>(&resource)?;
+    ///
+    ///     let data = iomem.try_access().ok_or(ENODEV)?.try_readl(offset)?;
+    ///
+    ///     iomem.try_access().ok_or(ENODEV)?.try_writel(data, offset)?;
+    ///
+    ///     # Ok::<(), Error>(())
+    /// }
+    /// ```
+    pub fn ioremap_resource<const EXCLUSIVE: bool>(
+        &self,
+        resource: &Resource,
+    ) -> Result<Devres<IoMem<0, EXCLUSIVE>>> {
+        self.ioremap_resource_sized::<0, EXCLUSIVE>(resource)
+    }
+
+    /// Returns the resource at `index`, if any.
+    pub fn resource(&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::from_ptr(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::from_ptr(resource) })
+    }
 }
 
 impl AsRef<device::Device> for Device {
-- 
2.48.0

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

[Christian Schrefl]

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

Re: [PATCH RESEND v5 2/3] rust: io: mem: add a generic iomem abstraction

[Christian Schrefl]

Hi Daniel

On 16.01.25 1:56 PM, 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     | 10 +++++
>  rust/kernel/io.rs     |  1 +
>  rust/kernel/io/mem.rs | 98 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 109 insertions(+)
>  create mode 100644 rust/kernel/io/mem.rs
> 
> diff --git a/rust/helpers/io.c b/rust/helpers/io.c
> index 3cb47bd01942..cb10060c08ae 100644
> --- a/rust/helpers/io.c
> +++ b/rust/helpers/io.c
> @@ -106,3 +106,13 @@ 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);
> +}
> diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
> index 566d8b177e01..9ce3482b5ecd 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;
>  
>  /// Raw representation of an MMIO region.
> diff --git a/rust/kernel/io/mem.rs b/rust/kernel/io/mem.rs
> new file mode 100644
> index 000000000000..a287dc0898e0
> --- /dev/null
> +++ b/rust/kernel/io/mem.rs
> @@ -0,0 +1,98 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Generic memory-mapped IO.
> +
> +use core::ops::Deref;
> +
> +use crate::device::Device;
> +use crate::devres::Devres;
> +use crate::io::resource::Resource;
> +use crate::io::Io;
> +use crate::io::IoRaw;
> +use crate::prelude::*;
> +
> +/// 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.
> +///
> +/// Whether `IoMem` represents an exclusive access to the underlying memory
> +/// region is determined by the caller at creation time, as overlapping access
> +/// may be needed in some cases.
> +///
> +/// # Invariants
> +///
> +/// `IoMem` always holds an `IoRaw` inststance that holds a valid pointer to the
> +/// start of the I/O memory mapped region.
> +pub struct IoMem<const SIZE: usize = 0, const EXCLUSIVE: bool = true> {
> +    io: IoRaw<SIZE>,
> +    res_start: u64,

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

> +}
> +
> +impl<const SIZE: usize, const EXCLUSIVE: bool> IoMem<SIZE, EXCLUSIVE> {
> +    /// Creates a new `IoMem` instance.
> +    pub(crate) fn new(resource: &Resource, device: &Device) -> Result<Devres<Self>> {
> +        let size = resource.size();
> +        if size == 0 {
> +            return Err(EINVAL);
> +        }
> +
> +        let res_start = resource.start();
> +
> +        if EXCLUSIVE {
> +            // SAFETY:
> +            // - `res_start` and `size` are read from a presumably valid `struct resource`.
> +            // - `size` is known not to be zero at this point.
> +            // - `resource.name()` returns a valid C string.
> +            let mem_region = unsafe {
> +                bindings::request_mem_region(res_start, size, resource.name().as_char_ptr())
> +            };
> +
> +            if mem_region.is_null() {
> +                return Err(EBUSY);
> +            }
> +        }
> +
> +        // SAFETY:
> +        // - `res_start` and `size` are read from a presumably valid `struct resource`.
> +        // - `size` is known not to be zero at this point.
> +        let addr = unsafe { bindings::ioremap(res_start, size as kernel::ffi::c_ulong) };
> +        if addr.is_null() {
> +            if EXCLUSIVE {
> +                // SAFETY:
> +                // - `res_start` and `size` are read from a presumably valid `struct resource`.
> +                // - `size` is the same as the one passed to `request_mem_region`.
> +                unsafe { bindings::release_mem_region(res_start, size) };
> +            }
> +            return Err(ENOMEM);
> +        }
> +
> +        let io = IoRaw::new(addr as usize, size as usize)?;
> +        let io = IoMem { io, res_start };
> +        let devres = Devres::new(device, io, GFP_KERNEL)?;
> +
> +        Ok(devres)
> +    }
> +}
> +
> +impl<const SIZE: usize, const EXCLUSIVE: bool> Drop for IoMem<SIZE, EXCLUSIVE> {
> +    fn drop(&mut self) {
> +        if EXCLUSIVE {
> +            // SAFETY: `res_start` and `io.maxsize()` were the values passed to
> +            // `request_mem_region`.
> +            unsafe { bindings::release_mem_region(self.res_start, self.io.maxsize() as u64) }

Please use bindings::resource_size_t here as well.

> +        }
> +
> +        // SAFETY: Safe as by the invariant of `Io`.
> +        unsafe { bindings::iounmap(self.io.addr() as *mut core::ffi::c_void) }
> +    }
> +}
> +
> +impl<const SIZE: usize, const EXCLUSIVE: bool> Deref for IoMem<SIZE, EXCLUSIVE> {
> +    type Target = Io<SIZE>;
> +
> +    fn deref(&self) -> &Self::Target {
> +        // SAFETY: Safe as by the invariant of `IoMem`.
> +        unsafe { Io::from_raw(&self.io) }
> +    }
> +}

Cheers
Christian

Re: [PATCH RESEND v5 0/3] rust: platform: add Io support

[Christian Schrefl]

Hi Daniel

On 16.01.25 1:56 PM, Daniel Almeida wrote:
> 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               |  17 ++++++
>  rust/kernel/io.rs               |   3 +
>  rust/kernel/io/mem.rs           |  98 +++++++++++++++++++++++++++++
>  rust/kernel/io/resource.rs      |  53 ++++++++++++++++
>  rust/kernel/platform.rs         | 105 +++++++++++++++++++++++++++++++-
>  6 files changed, 276 insertions(+), 1 deletion(-)
>  create mode 100644 rust/kernel/io/mem.rs
>  create mode 100644 rust/kernel/io/resource.rs
> 


I've tested this patch-set with my ARM 32-bit arm patches[0] on a De1Soc (Fpga + Arm Cortex A9).

I've got it to work by changing the three instances of u64 (mentioned on the individual patches) to bindings::resource_size_t.
I used a small Fpga configuration that allows me to change a led from the kernel driver.

So with these fixed:

Tested-by: Christian Schrefl <chrisi.schrefl@gmail.com>

[0]: https://github.com/onestacked/linux/commit/f84be45f7311ea5b5a76123028f9fb8fda9f9e7f

Cheers
Christian