[PATCH v3 0/5] rust: pci: add config space read/write support

[PATCH v3 0/5] rust: pci: add config space read/write support

[Zhi Wang]

In the NVIDIA vGPU RFC [1], the PCI configuration space access is
required in nova-core for preparing gspVFInfo when vGPU support is
enabled. This series is the following up of the discussion with Danilo
for how to introduce support of PCI configuration space access in Rust
PCI abstrations.

v3:

- Turn offset_valid() into a private function of kernel::io:Io. (Alex)
- Separate try and non-try variants. (Danilo)
- Move all the {try_}{read,write}{8,16,32,64} accessors to the I/O trait.
  (Danilo)
- Replace the hardcoded MMIO type constraint with a generic trait bound
  so that register! macro can be used in other places. (Danilo)
- Fix doctest. (John)
- Add an enum for PCI configuration space size. (Danilo)
- Refine the patch comments. (Bjorn)

This ideas of this series are:

- Factor out a common trait IoRegion for other accessors to share the
  same compiling/runtime check like before.

- Factor the MMIO read/write macros from the define_read! and
  define_write! macros. Thus, define_{read, write}! can be used in other
  backend.

  In detail:

  * Introduce `call_mmio_read!` and `call_mmio_write!` helper macros
    to encapsulate the unsafe FFI calls.
  * Update `define_read!` and `define_write!` macros to delegate to
    the call macros.
  * Export `define_read` and `define_write` so they can be reused
    for other I/O backends (e.g. PCI config space).

- Add a helper to query configuration space size. This is mostly for
  runtime check.

- Implement the PCI configuration space access backend in PCI
  Abstractions.

- Add tests for config space routines in rust PCI sample driver.

Zhi Wang (5):
  rust: io: factor common I/O helpers into Io trait and specialize
    Mmio<SIZE>
  rust: io: factor out MMIO read/write macros
  rust: pci: add a helper to query configuration space size
  rust: pci: add config space read/write support
  sample: rust: pci: add tests for config space routines

 drivers/gpu/nova-core/regs/macros.rs |  90 +++++---
 drivers/gpu/nova-core/vbios.rs       |   1 +
 rust/kernel/devres.rs                |  12 +-
 rust/kernel/io.rs                    | 333 +++++++++++++++++++++------
 rust/kernel/io/mem.rs                |  16 +-
 rust/kernel/io/poll.rs               |   4 +-
 rust/kernel/pci.rs                   |  94 +++++++-
 samples/rust/rust_driver_pci.rs      |  28 ++-
 8 files changed, 444 insertions(+), 134 deletions(-)

-- 
2.47.3

[PATCH v3 1/5] rust: io: factor common I/O helpers into Io trait

[Zhi Wang]

The previous Io<SIZE> type combined both the generic I/O access helpers
and MMIO implementation details in a single struct.

To establish a cleaner layering between the I/O interface and its concrete
backends, paving the way for supporting additional I/O mechanisms in the
future, Io<SIZE> need to be factored.

Factor the common helpers into a new Io trait, and move the MMIO-specific
logic into a dedicated Mmio<SIZE> type implementing that trait. Rename the
IoRaw to MmioRaw and update the bus MMIO implementations to use MmioRaw.

No functional change intended.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Bjorn Helgaas <helgaas@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 drivers/gpu/nova-core/regs/macros.rs |  90 +++++----
 drivers/gpu/nova-core/vbios.rs       |   1 +
 rust/kernel/devres.rs                |  12 +-
 rust/kernel/io.rs                    | 279 ++++++++++++++++++++-------
 rust/kernel/io/mem.rs                |  16 +-
 rust/kernel/io/poll.rs               |   4 +-
 rust/kernel/pci.rs                   |  10 +-
 samples/rust/rust_driver_pci.rs      |   2 +-
 8 files changed, 289 insertions(+), 125 deletions(-)

diff --git a/drivers/gpu/nova-core/regs/macros.rs b/drivers/gpu/nova-core/regs/macros.rs
index fd1a815fa57d..80daaa486bc1 100644
--- a/drivers/gpu/nova-core/regs/macros.rs
+++ b/drivers/gpu/nova-core/regs/macros.rs
@@ -369,16 +369,18 @@ impl $name {
 
             /// Read the register from its address in `io`.
             #[inline(always)]
-            pub(crate) fn read<const SIZE: usize, T>(io: &T) -> Self where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+            pub(crate) fn read<const SIZE: usize, T, I>(io: &T) -> Self where
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
             {
                 Self(io.read32($offset))
             }
 
             /// Write the value contained in `self` to the register address in `io`.
             #[inline(always)]
-            pub(crate) fn write<const SIZE: usize, T>(self, io: &T) where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+            pub(crate) fn write<const SIZE: usize, T, I>(self, io: &T) where
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
             {
                 io.write32(self.0, $offset)
             }
@@ -386,11 +388,12 @@ pub(crate) fn write<const SIZE: usize, T>(self, io: &T) where
             /// Read the register from its address in `io` and run `f` on its value to obtain a new
             /// value to write back.
             #[inline(always)]
-            pub(crate) fn update<const SIZE: usize, T, F>(
+            pub(crate) fn update<const SIZE: usize, T, I, F>(
                 io: &T,
                 f: F,
             ) where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 F: ::core::ops::FnOnce(Self) -> Self,
             {
                 let reg = f(Self::read(io));
@@ -408,12 +411,13 @@ impl $name {
             /// Read the register from `io`, using the base address provided by `base` and adding
             /// the register's offset to it.
             #[inline(always)]
-            pub(crate) fn read<const SIZE: usize, T, B>(
+            pub(crate) fn read<const SIZE: usize, T, I, B>(
                 io: &T,
                 #[allow(unused_variables)]
                 base: &B,
             ) -> Self where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
             {
                 const OFFSET: usize = $name::OFFSET;
@@ -428,13 +432,14 @@ pub(crate) fn read<const SIZE: usize, T, B>(
             /// Write the value contained in `self` to `io`, using the base address provided by
             /// `base` and adding the register's offset to it.
             #[inline(always)]
-            pub(crate) fn write<const SIZE: usize, T, B>(
+            pub(crate) fn write<const SIZE: usize, T, I, B>(
                 self,
                 io: &T,
                 #[allow(unused_variables)]
                 base: &B,
             ) where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
             {
                 const OFFSET: usize = $name::OFFSET;
@@ -449,12 +454,13 @@ pub(crate) fn write<const SIZE: usize, T, B>(
             /// the register's offset to it, then run `f` on its value to obtain a new value to
             /// write back.
             #[inline(always)]
-            pub(crate) fn update<const SIZE: usize, T, B, F>(
+            pub(crate) fn update<const SIZE: usize, T, I, B, F>(
                 io: &T,
                 base: &B,
                 f: F,
             ) where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
                 F: ::core::ops::FnOnce(Self) -> Self,
             {
@@ -474,11 +480,12 @@ impl $name {
 
             /// Read the array register at index `idx` from its address in `io`.
             #[inline(always)]
-            pub(crate) fn read<const SIZE: usize, T>(
+            pub(crate) fn read<const SIZE: usize, T, I>(
                 io: &T,
                 idx: usize,
             ) -> Self where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
             {
                 build_assert!(idx < Self::SIZE);
 
@@ -490,12 +497,13 @@ pub(crate) fn read<const SIZE: usize, T>(
 
             /// Write the value contained in `self` to the array register with index `idx` in `io`.
             #[inline(always)]
-            pub(crate) fn write<const SIZE: usize, T>(
+            pub(crate) fn write<const SIZE: usize, T, I>(
                 self,
                 io: &T,
                 idx: usize
             ) where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
             {
                 build_assert!(idx < Self::SIZE);
 
@@ -507,12 +515,13 @@ pub(crate) fn write<const SIZE: usize, T>(
             /// Read the array register at index `idx` in `io` and run `f` on its value to obtain a
             /// new value to write back.
             #[inline(always)]
-            pub(crate) fn update<const SIZE: usize, T, F>(
+            pub(crate) fn update<const SIZE: usize, T, I, F>(
                 io: &T,
                 idx: usize,
                 f: F,
             ) where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 F: ::core::ops::FnOnce(Self) -> Self,
             {
                 let reg = f(Self::read(io, idx));
@@ -524,11 +533,12 @@ pub(crate) fn update<const SIZE: usize, T, F>(
             /// The validity of `idx` is checked at run-time, and `EINVAL` is returned is the
             /// access was out-of-bounds.
             #[inline(always)]
-            pub(crate) fn try_read<const SIZE: usize, T>(
+            pub(crate) fn try_read<const SIZE: usize, T, I>(
                 io: &T,
                 idx: usize,
             ) -> ::kernel::error::Result<Self> where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
             {
                 if idx < Self::SIZE {
                     Ok(Self::read(io, idx))
@@ -542,12 +552,13 @@ pub(crate) fn try_read<const SIZE: usize, T>(
             /// The validity of `idx` is checked at run-time, and `EINVAL` is returned is the
             /// access was out-of-bounds.
             #[inline(always)]
-            pub(crate) fn try_write<const SIZE: usize, T>(
+            pub(crate) fn try_write<const SIZE: usize, T, I>(
                 self,
                 io: &T,
                 idx: usize,
             ) -> ::kernel::error::Result where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
             {
                 if idx < Self::SIZE {
                     Ok(self.write(io, idx))
@@ -562,12 +573,13 @@ pub(crate) fn try_write<const SIZE: usize, T>(
             /// The validity of `idx` is checked at run-time, and `EINVAL` is returned is the
             /// access was out-of-bounds.
             #[inline(always)]
-            pub(crate) fn try_update<const SIZE: usize, T, F>(
+            pub(crate) fn try_update<const SIZE: usize, T, I, F>(
                 io: &T,
                 idx: usize,
                 f: F,
             ) -> ::kernel::error::Result where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 F: ::core::ops::FnOnce(Self) -> Self,
             {
                 if idx < Self::SIZE {
@@ -593,13 +605,14 @@ impl $name {
             /// Read the array register at index `idx` from `io`, using the base address provided
             /// by `base` and adding the register's offset to it.
             #[inline(always)]
-            pub(crate) fn read<const SIZE: usize, T, B>(
+            pub(crate) fn read<const SIZE: usize, T, I, B>(
                 io: &T,
                 #[allow(unused_variables)]
                 base: &B,
                 idx: usize,
             ) -> Self where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
             {
                 build_assert!(idx < Self::SIZE);
@@ -614,14 +627,15 @@ pub(crate) fn read<const SIZE: usize, T, B>(
             /// Write the value contained in `self` to `io`, using the base address provided by
             /// `base` and adding the offset of array register `idx` to it.
             #[inline(always)]
-            pub(crate) fn write<const SIZE: usize, T, B>(
+            pub(crate) fn write<const SIZE: usize, T, I, B>(
                 self,
                 io: &T,
                 #[allow(unused_variables)]
                 base: &B,
                 idx: usize
             ) where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
             {
                 build_assert!(idx < Self::SIZE);
@@ -636,13 +650,14 @@ pub(crate) fn write<const SIZE: usize, T, B>(
             /// by `base` and adding the register's offset to it, then run `f` on its value to
             /// obtain a new value to write back.
             #[inline(always)]
-            pub(crate) fn update<const SIZE: usize, T, B, F>(
+            pub(crate) fn update<const SIZE: usize, T, I, B, F>(
                 io: &T,
                 base: &B,
                 idx: usize,
                 f: F,
             ) where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
                 F: ::core::ops::FnOnce(Self) -> Self,
             {
@@ -656,12 +671,13 @@ pub(crate) fn update<const SIZE: usize, T, B, F>(
             /// The validity of `idx` is checked at run-time, and `EINVAL` is returned is the
             /// access was out-of-bounds.
             #[inline(always)]
-            pub(crate) fn try_read<const SIZE: usize, T, B>(
+            pub(crate) fn try_read<const SIZE: usize, T, I, B>(
                 io: &T,
                 base: &B,
                 idx: usize,
             ) -> ::kernel::error::Result<Self> where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
             {
                 if idx < Self::SIZE {
@@ -677,13 +693,14 @@ pub(crate) fn try_read<const SIZE: usize, T, B>(
             /// The validity of `idx` is checked at run-time, and `EINVAL` is returned is the
             /// access was out-of-bounds.
             #[inline(always)]
-            pub(crate) fn try_write<const SIZE: usize, T, B>(
+            pub(crate) fn try_write<const SIZE: usize, T, I, B>(
                 self,
                 io: &T,
                 base: &B,
                 idx: usize,
             ) -> ::kernel::error::Result where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
             {
                 if idx < Self::SIZE {
@@ -700,13 +717,14 @@ pub(crate) fn try_write<const SIZE: usize, T, B>(
             /// The validity of `idx` is checked at run-time, and `EINVAL` is returned is the
             /// access was out-of-bounds.
             #[inline(always)]
-            pub(crate) fn try_update<const SIZE: usize, T, B, F>(
+            pub(crate) fn try_update<const SIZE: usize, T, I, B, F>(
                 io: &T,
                 base: &B,
                 idx: usize,
                 f: F,
             ) -> ::kernel::error::Result where
-                T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
+                T: ::core::ops::Deref<Target = I>,
+                I: ::kernel::io::Io<SIZE>,
                 B: crate::regs::macros::RegisterBase<$base>,
                 F: ::core::ops::FnOnce(Self) -> Self,
             {
diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
index 74ed6d61e6cc..cafb2d99c82b 100644
--- a/drivers/gpu/nova-core/vbios.rs
+++ b/drivers/gpu/nova-core/vbios.rs
@@ -10,6 +10,7 @@
 use kernel::error::Result;
 use kernel::prelude::*;
 use kernel::ptr::{Alignable, Alignment};
+use kernel::io::Io;
 use kernel::types::ARef;
 
 /// The offset of the VBIOS ROM in the BAR0 space.
diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
index 10a6a1789854..12a4474df3c3 100644
--- a/rust/kernel/devres.rs
+++ b/rust/kernel/devres.rs
@@ -52,11 +52,11 @@ struct Inner<T: Send> {
 /// # Examples
 ///
 /// ```no_run
-/// # use kernel::{bindings, device::{Bound, Device}, devres::Devres, io::{Io, IoRaw}};
+/// # use kernel::{bindings, device::{Bound, Device}, devres::Devres, io::{Io, Mmio, MmioRaw}};
 /// # use core::ops::Deref;
 ///
 /// // See also [`pci::Bar`] for a real example.
-/// struct IoMem<const SIZE: usize>(IoRaw<SIZE>);
+/// struct IoMem<const SIZE: usize>(MmioRaw<SIZE>);
 ///
 /// impl<const SIZE: usize> IoMem<SIZE> {
 ///     /// # Safety
@@ -71,7 +71,7 @@ struct Inner<T: Send> {
 ///             return Err(ENOMEM);
 ///         }
 ///
-///         Ok(IoMem(IoRaw::new(addr as usize, SIZE)?))
+///         Ok(IoMem(MmioRaw::new(addr as usize, SIZE)?))
 ///     }
 /// }
 ///
@@ -83,11 +83,11 @@ struct Inner<T: Send> {
 /// }
 ///
 /// impl<const SIZE: usize> Deref for IoMem<SIZE> {
-///    type Target = Io<SIZE>;
+///    type Target = Mmio<SIZE>;
 ///
 ///    fn deref(&self) -> &Self::Target {
 ///         // SAFETY: The memory range stored in `self` has been properly mapped in `Self::new`.
-///         unsafe { Io::from_raw(&self.0) }
+///         unsafe { Mmio::from_raw(&self.0) }
 ///    }
 /// }
 /// # fn no_run(dev: &Device<Bound>) -> Result<(), Error> {
@@ -230,7 +230,7 @@ pub fn device(&self) -> &Device {
     ///
     /// ```no_run
     /// # #![cfg(CONFIG_PCI)]
-    /// # use kernel::{device::Core, devres::Devres, pci};
+    /// # use kernel::{device::Core, devres::Devres, io::Io, pci};
     ///
     /// fn from_core(dev: &pci::Device<Core>, devres: Devres<pci::Bar<0x4>>) -> Result {
     ///     let bar = devres.access(dev.as_ref())?;
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index ee182b0b5452..0b48edabf39a 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -4,7 +4,7 @@
 //!
 //! C header: [`include/asm-generic/io.h`](srctree/include/asm-generic/io.h)
 
-use crate::error::{code::EINVAL, Result};
+use crate::error::{code::EINVAL, code::ENOTSUPP, Result};
 use crate::{bindings, build_assert, ffi::c_void};
 
 pub mod mem;
@@ -18,16 +18,16 @@
 /// By itself, the existence of an instance of this structure does not provide any guarantees that
 /// the represented MMIO region does exist or is properly mapped.
 ///
-/// Instead, the bus specific MMIO implementation must convert this raw representation into an `Io`
-/// instance providing the actual memory accessors. Only by the conversion into an `Io` structure
-/// any guarantees are given.
-pub struct IoRaw<const SIZE: usize = 0> {
+/// Instead, the bus specific MMIO implementation must convert this raw representation into an
+/// `Mmio` instance providing the actual memory accessors. Only by the conversion into an `Mmio`
+/// structure any guarantees are given.
+pub struct MmioRaw<const SIZE: usize = 0> {
     addr: usize,
     maxsize: usize,
 }
 
-impl<const SIZE: usize> IoRaw<SIZE> {
-    /// Returns a new `IoRaw` instance on success, an error otherwise.
+impl<const SIZE: usize> MmioRaw<SIZE> {
+    /// Returns a new `MmioRaw` instance on success, an error otherwise.
     pub fn new(addr: usize, maxsize: usize) -> Result<Self> {
         if maxsize < SIZE {
             return Err(EINVAL);
@@ -62,11 +62,11 @@ pub fn maxsize(&self) -> usize {
 /// # Examples
 ///
 /// ```no_run
-/// # use kernel::{bindings, ffi::c_void, io::{Io, IoRaw}};
+/// # use kernel::{bindings, ffi::c_void, io::{Io, Mmio, MmioRaw}};
 /// # use core::ops::Deref;
 ///
 /// // See also [`pci::Bar`] for a real example.
-/// struct IoMem<const SIZE: usize>(IoRaw<SIZE>);
+/// struct IoMem<const SIZE: usize>(MmioRaw<SIZE>);
 ///
 /// impl<const SIZE: usize> IoMem<SIZE> {
 ///     /// # Safety
@@ -81,7 +81,7 @@ pub fn maxsize(&self) -> usize {
 ///             return Err(ENOMEM);
 ///         }
 ///
-///         Ok(IoMem(IoRaw::new(addr as usize, SIZE)?))
+///         Ok(IoMem(MmioRaw::new(addr as usize, SIZE)?))
 ///     }
 /// }
 ///
@@ -93,11 +93,11 @@ pub fn maxsize(&self) -> usize {
 /// }
 ///
 /// impl<const SIZE: usize> Deref for IoMem<SIZE> {
-///    type Target = Io<SIZE>;
+///    type Target = Mmio<SIZE>;
 ///
 ///    fn deref(&self) -> &Self::Target {
 ///         // SAFETY: The memory range stored in `self` has been properly mapped in `Self::new`.
-///         unsafe { Io::from_raw(&self.0) }
+///         unsafe { Mmio::from_raw(&self.0) }
 ///    }
 /// }
 ///
@@ -111,29 +111,31 @@ pub fn maxsize(&self) -> usize {
 /// # }
 /// ```
 #[repr(transparent)]
-pub struct Io<const SIZE: usize = 0>(IoRaw<SIZE>);
+pub struct Mmio<const SIZE: usize = 0>(MmioRaw<SIZE>);
 
 macro_rules! define_read {
-    ($(#[$attr:meta])* $name:ident, $try_name:ident, $c_fn:ident -> $type_name:ty) => {
+    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $c_fn:ident -> $type_name:ty) => {
         /// Read IO data from a given offset known at compile time.
         ///
         /// Bound checks are performed on compile time, hence if the offset is not known at compile
         /// time, the build will fail.
         $(#[$attr])*
         #[inline]
-        pub fn $name(&self, offset: usize) -> $type_name {
+        $vis fn $name(&self, offset: usize) -> $type_name {
             let addr = self.io_addr_assert::<$type_name>(offset);
 
             // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
             unsafe { bindings::$c_fn(addr as *const c_void) }
         }
+    };
 
+    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $c_fn:ident -> $type_name:ty) => {
         /// Read IO data from a given offset.
         ///
         /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
         /// out of bounds.
         $(#[$attr])*
-        pub fn $try_name(&self, offset: usize) -> Result<$type_name> {
+        $vis fn $try_name(&self, offset: usize) -> Result<$type_name> {
             let addr = self.io_addr::<$type_name>(offset)?;
 
             // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
@@ -143,26 +145,28 @@ pub fn $try_name(&self, offset: usize) -> Result<$type_name> {
 }
 
 macro_rules! define_write {
-    ($(#[$attr:meta])* $name:ident, $try_name:ident, $c_fn:ident <- $type_name:ty) => {
+    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $c_fn:ident <- $type_name:ty) => {
         /// Write IO data from a given offset known at compile time.
         ///
         /// Bound checks are performed on compile time, hence if the offset is not known at compile
         /// time, the build will fail.
         $(#[$attr])*
         #[inline]
-        pub fn $name(&self, value: $type_name, offset: usize) {
+        $vis fn $name(&self, value: $type_name, offset: usize) {
             let addr = self.io_addr_assert::<$type_name>(offset);
 
             // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
             unsafe { bindings::$c_fn(value, addr as *mut c_void) }
         }
+    };
 
+    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $c_fn:ident <- $type_name:ty) => {
         /// Write IO data from a given offset.
         ///
         /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
         /// out of bounds.
         $(#[$attr])*
-        pub fn $try_name(&self, value: $type_name, offset: usize) -> Result {
+        $vis fn $try_name(&self, value: $type_name, offset: usize) -> Result {
             let addr = self.io_addr::<$type_name>(offset)?;
 
             // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
@@ -172,43 +176,37 @@ pub fn $try_name(&self, value: $type_name, offset: usize) -> Result {
     };
 }
 
-impl<const SIZE: usize> Io<SIZE> {
-    /// Converts an `IoRaw` into an `Io` instance, providing the accessors to the MMIO mapping.
-    ///
-    /// # Safety
-    ///
-    /// Callers must ensure that `addr` is the start of a valid I/O mapped memory region of size
-    /// `maxsize`.
-    pub unsafe fn from_raw(raw: &IoRaw<SIZE>) -> &Self {
-        // SAFETY: `Io` is a transparent wrapper around `IoRaw`.
-        unsafe { &*core::ptr::from_ref(raw).cast() }
+/// Checks whether an access of type `U` at the given `offset`
+/// is valid within this region.
+#[inline]
+const fn offset_valid<U>(offset: usize, size: usize) -> bool {
+    let type_size = core::mem::size_of::<U>();
+    if let Some(end) = offset.checked_add(type_size) {
+        end <= size && offset % type_size == 0
+    } else {
+        false
     }
+}
 
+/// Represents a region of I/O space of a fixed size.
+///
+/// Provides common helpers for offset validation and address
+/// calculation on top of a base address and maximum size.
+///
+/// Types implementing this trait (e.g. MMIO BARs or PCI config
+/// regions) can share the same accessors.
+pub trait Io<const SIZE: usize> {
     /// Returns the base address of this mapping.
-    #[inline]
-    pub fn addr(&self) -> usize {
-        self.0.addr()
-    }
+    fn addr(&self) -> usize;
 
     /// Returns the maximum size of this mapping.
-    #[inline]
-    pub fn maxsize(&self) -> usize {
-        self.0.maxsize()
-    }
-
-    #[inline]
-    const fn offset_valid<U>(offset: usize, size: usize) -> bool {
-        let type_size = core::mem::size_of::<U>();
-        if let Some(end) = offset.checked_add(type_size) {
-            end <= size && offset % type_size == 0
-        } else {
-            false
-        }
-    }
+    fn maxsize(&self) -> usize;
 
+    /// Returns the absolute I/O address for a given `offset`.
+    /// Performs runtime bounds checks using [`offset_valid`]
     #[inline]
     fn io_addr<U>(&self, offset: usize) -> Result<usize> {
-        if !Self::offset_valid::<U>(offset, self.maxsize()) {
+        if !offset_valid::<U>(offset, self.maxsize()) {
             return Err(EINVAL);
         }
 
@@ -217,50 +215,197 @@ fn io_addr<U>(&self, offset: usize) -> Result<usize> {
         self.addr().checked_add(offset).ok_or(EINVAL)
     }
 
+    /// Returns the absolute I/O address for a given `offset`,
+    /// performing compile-time bound checks.
     #[inline]
     fn io_addr_assert<U>(&self, offset: usize) -> usize {
-        build_assert!(Self::offset_valid::<U>(offset, SIZE));
+        build_assert!(offset_valid::<U>(offset, SIZE));
 
         self.addr() + offset
     }
 
-    define_read!(read8, try_read8, readb -> u8);
-    define_read!(read16, try_read16, readw -> u16);
-    define_read!(read32, try_read32, readl -> u32);
+    /// Infallible 8-bit read with compile-time bounds check.
+    fn read8(&self, _offset: usize) -> u8 {
+        !0
+    }
+
+    /// Infallible 16-bit read with compile-time bounds check.
+    fn read16(&self, _offset: usize) -> u16 {
+        !0
+    }
+
+    /// Infallible 32-bit read with compile-time bounds check.
+    fn read32(&self, _offset: usize) -> u32 {
+        !0
+    }
+
+    /// Infallible 64-bit read with compile-time bounds check (64-bit only).
+    #[cfg(CONFIG_64BIT)]
+    fn read64(&self, _offset: usize) -> u64 {
+        !0
+    }
+
+    /// Fallible 8-bit read with runtime bounds check.
+    fn try_read8(&self, _offset: usize) -> Result<u8> {
+        Err(ENOTSUPP)
+    }
+
+    /// Fallible 16-bit read with runtime bounds check.
+    fn try_read16(&self, _offset: usize) -> Result<u16> {
+        Err(ENOTSUPP)
+    }
+
+    /// Fallible 32-bit read with runtime bounds check.
+    fn try_read32(&self, _offset: usize) -> Result<u32> {
+        Err(ENOTSUPP)
+    }
+
+    /// Fallible 64-bit read with runtime bounds check (64-bit only).
+    #[cfg(CONFIG_64BIT)]
+    fn try_read64(&self, _offset: usize) -> Result<u64> {
+        Err(ENOTSUPP)
+    }
+
+    /// Infallible 8-bit write with compile-time bounds check.
+    fn write8(&self, _value: u8, _offset: usize) {
+        ()
+    }
+
+    /// Infallible 16-bit write with compile-time bounds check.
+    fn write16(&self, _value: u16, _offset: usize) {
+        ()
+    }
+
+    /// Infallible 32-bit write with compile-time bounds check.
+    fn write32(&self, _value: u32, _offset: usize) {
+        ()
+    }
+
+    /// Infallible 64-bit write with compile-time bounds check (64-bit only).
+    #[cfg(CONFIG_64BIT)]
+    fn write64(&self, _value: u64, _offset: usize) {
+        ()
+    }
+
+    /// Fallible 8-bit write with runtime bounds check.
+    fn try_write8(&self, value: u8, offset: usize) -> Result;
+
+    /// Fallible 16-bit write with runtime bounds check.
+    fn try_write16(&self, value: u16, offset: usize) -> Result;
+
+    /// Fallible 32-bit write with runtime bounds check.
+    fn try_write32(&self, value: u32, offset: usize) -> Result;
+
+    /// Fallible 64-bit write with runtime bounds check (64-bit only).
+    #[cfg(CONFIG_64BIT)]
+    fn try_write64(&self, _value: u64, _offset: usize) -> Result {
+        Err(ENOTSUPP)
+    }
+}
+
+impl<const SIZE: usize> Io<SIZE> for Mmio<SIZE> {
+    /// Returns the base address of this mapping.
+    #[inline]
+    fn addr(&self) -> usize {
+        self.0.addr()
+    }
+
+    /// Returns the maximum size of this mapping.
+    #[inline]
+    fn maxsize(&self) -> usize {
+        self.0.maxsize()
+    }
+
+    define_read!(infallible, read8, readb -> u8);
+    define_read!(infallible, read16, readw -> u16);
+    define_read!(infallible, read32, readl -> u32);
     define_read!(
+        infallible,
         #[cfg(CONFIG_64BIT)]
         read64,
-        try_read64,
         readq -> u64
     );
 
-    define_read!(read8_relaxed, try_read8_relaxed, readb_relaxed -> u8);
-    define_read!(read16_relaxed, try_read16_relaxed, readw_relaxed -> u16);
-    define_read!(read32_relaxed, try_read32_relaxed, readl_relaxed -> u32);
+    define_read!(fallible, try_read8, readb -> u8);
+    define_read!(fallible, try_read16, readw -> u16);
+    define_read!(fallible, try_read32, readl -> u32);
     define_read!(
+        fallible,
         #[cfg(CONFIG_64BIT)]
-        read64_relaxed,
-        try_read64_relaxed,
-        readq_relaxed -> u64
+        try_read64,
+        readq -> u64
     );
 
-    define_write!(write8, try_write8, writeb <- u8);
-    define_write!(write16, try_write16, writew <- u16);
-    define_write!(write32, try_write32, writel <- u32);
+    define_write!(infallible, write8, writeb <- u8);
+    define_write!(infallible, write16, writew <- u16);
+    define_write!(infallible, write32, writel <- u32);
     define_write!(
+        infallible,
         #[cfg(CONFIG_64BIT)]
         write64,
+        writeq <- u64
+    );
+
+    define_write!(fallible, try_write8, writeb <- u8);
+    define_write!(fallible, try_write16, writew <- u16);
+    define_write!(fallible, try_write32, writel <- u32);
+    define_write!(
+        fallible,
+        #[cfg(CONFIG_64BIT)]
         try_write64,
         writeq <- u64
     );
+}
+
+impl<const SIZE: usize> Mmio<SIZE> {
+    /// Converts an `MmioRaw` into an `Mmio` instance, providing the accessors to the MMIO mapping.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `addr` is the start of a valid I/O mapped memory region of size
+    /// `maxsize`.
+    pub unsafe fn from_raw(raw: &MmioRaw<SIZE>) -> &Self {
+        // SAFETY: `Mmio` is a transparent wrapper around `MmioRaw`.
+        unsafe { &*core::ptr::from_ref(raw).cast() }
+    }
+
+    define_read!(infallible, pub read8_relaxed, readb_relaxed -> u8);
+    define_read!(infallible, pub read16_relaxed, readw_relaxed -> u16);
+    define_read!(infallible, pub read32_relaxed, readl_relaxed -> u32);
+    define_read!(
+        infallible,
+        #[cfg(CONFIG_64BIT)]
+        pub read64_relaxed,
+        readq_relaxed -> u64
+    );
+
+    define_read!(fallible, pub try_read8_relaxed, readb_relaxed -> u8);
+    define_read!(fallible, pub try_read16_relaxed, readw_relaxed -> u16);
+    define_read!(fallible, pub try_read32_relaxed, readl_relaxed -> u32);
+    define_read!(
+        fallible,
+        #[cfg(CONFIG_64BIT)]
+        pub try_read64_relaxed,
+        readq_relaxed -> u64
+    );
+
+    define_write!(infallible, pub write8_relaxed, writeb_relaxed <- u8);
+    define_write!(infallible, pub write16_relaxed, writew_relaxed <- u16);
+    define_write!(infallible, pub write32_relaxed, writel_relaxed <- u32);
+    define_write!(
+        infallible,
+        #[cfg(CONFIG_64BIT)]
+        pub write64_relaxed,
+        writeq_relaxed <- u64
+    );
 
-    define_write!(write8_relaxed, try_write8_relaxed, writeb_relaxed <- u8);
-    define_write!(write16_relaxed, try_write16_relaxed, writew_relaxed <- u16);
-    define_write!(write32_relaxed, try_write32_relaxed, writel_relaxed <- u32);
+    define_write!(fallible, pub try_write8_relaxed, writeb_relaxed <- u8);
+    define_write!(fallible, pub try_write16_relaxed, writew_relaxed <- u16);
+    define_write!(fallible, pub try_write32_relaxed, writel_relaxed <- u32);
     define_write!(
+        fallible,
         #[cfg(CONFIG_64BIT)]
-        write64_relaxed,
-        try_write64_relaxed,
+        pub try_write64_relaxed,
         writeq_relaxed <- u64
     );
 }
diff --git a/rust/kernel/io/mem.rs b/rust/kernel/io/mem.rs
index 6f99510bfc3a..93cad8539b18 100644
--- a/rust/kernel/io/mem.rs
+++ b/rust/kernel/io/mem.rs
@@ -11,8 +11,8 @@
 use crate::io;
 use crate::io::resource::Region;
 use crate::io::resource::Resource;
-use crate::io::Io;
-use crate::io::IoRaw;
+use crate::io::Mmio;
+use crate::io::MmioRaw;
 use crate::prelude::*;
 
 /// An IO request for a specific device and resource.
@@ -195,7 +195,7 @@ pub fn new<'a>(io_request: IoRequest<'a>) -> impl PinInit<Devres<Self>, Error> +
 }
 
 impl<const SIZE: usize> Deref for ExclusiveIoMem<SIZE> {
-    type Target = Io<SIZE>;
+    type Target = Mmio<SIZE>;
 
     fn deref(&self) -> &Self::Target {
         &self.iomem
@@ -209,10 +209,10 @@ fn deref(&self) -> &Self::Target {
 ///
 /// # Invariants
 ///
-/// [`IoMem`] always holds an [`IoRaw`] instance that holds a valid pointer to the
+/// [`IoMem`] always holds an [`MmioRaw`] 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>,
+    io: MmioRaw<SIZE>,
 }
 
 impl<const SIZE: usize> IoMem<SIZE> {
@@ -247,7 +247,7 @@ fn ioremap(resource: &Resource) -> Result<Self> {
             return Err(ENOMEM);
         }
 
-        let io = IoRaw::new(addr as usize, size)?;
+        let io = MmioRaw::new(addr as usize, size)?;
         let io = IoMem { io };
 
         Ok(io)
@@ -270,10 +270,10 @@ fn drop(&mut self) {
 }
 
 impl<const SIZE: usize> Deref for IoMem<SIZE> {
-    type Target = Io<SIZE>;
+    type Target = Mmio<SIZE>;
 
     fn deref(&self) -> &Self::Target {
         // SAFETY: Safe as by the invariant of `IoMem`.
-        unsafe { Io::from_raw(&self.io) }
+        unsafe { Mmio::from_raw(&self.io) }
     }
 }
diff --git a/rust/kernel/io/poll.rs b/rust/kernel/io/poll.rs
index 613eb25047ef..a9fea091303b 100644
--- a/rust/kernel/io/poll.rs
+++ b/rust/kernel/io/poll.rs
@@ -37,12 +37,12 @@
 /// # Examples
 ///
 /// ```no_run
-/// use kernel::io::{Io, poll::read_poll_timeout};
+/// use kernel::io::{Io, Mmio, poll::read_poll_timeout};
 /// use kernel::time::Delta;
 ///
 /// const HW_READY: u16 = 0x01;
 ///
-/// fn wait_for_hardware<const SIZE: usize>(io: &Io<SIZE>) -> Result<()> {
+/// fn wait_for_hardware<const SIZE: usize>(io: &Mmio<SIZE>) -> Result<()> {
 ///     match read_poll_timeout(
 ///         // The `op` closure reads the value of a specific status register.
 ///         || io.try_read16(0x1000),
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 7fcc5f6022c1..77a8eb39ad32 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -10,7 +10,7 @@
     devres::Devres,
     driver,
     error::{from_result, to_result, Result},
-    io::{Io, IoRaw},
+    io::{Mmio, MmioRaw},
     irq::{self, IrqRequest},
     str::CStr,
     sync::aref::ARef,
@@ -313,7 +313,7 @@ pub struct Device<Ctx: device::DeviceContext = device::Normal>(
 /// memory mapped PCI bar and its size.
 pub struct Bar<const SIZE: usize = 0> {
     pdev: ARef<Device>,
-    io: IoRaw<SIZE>,
+    io: MmioRaw<SIZE>,
     num: i32,
 }
 
@@ -349,7 +349,7 @@ fn new(pdev: &Device, num: u32, name: &CStr) -> Result<Self> {
             return Err(ENOMEM);
         }
 
-        let io = match IoRaw::new(ioptr, len as usize) {
+        let io = match MmioRaw::new(ioptr, len as usize) {
             Ok(io) => io,
             Err(err) => {
                 // SAFETY:
@@ -403,11 +403,11 @@ fn drop(&mut self) {
 }
 
 impl<const SIZE: usize> Deref for Bar<SIZE> {
-    type Target = Io<SIZE>;
+    type Target = Mmio<SIZE>;
 
     fn deref(&self) -> &Self::Target {
         // SAFETY: By the type invariant of `Self`, the MMIO range in `self.io` is properly mapped.
-        unsafe { Io::from_raw(&self.io) }
+        unsafe { Mmio::from_raw(&self.io) }
     }
 }
 
diff --git a/samples/rust/rust_driver_pci.rs b/samples/rust/rust_driver_pci.rs
index 55a683c39ed9..528e672b6b89 100644
--- a/samples/rust/rust_driver_pci.rs
+++ b/samples/rust/rust_driver_pci.rs
@@ -4,7 +4,7 @@
 //!
 //! To make this driver probe, QEMU must be run with `-device pci-testdev`.
 
-use kernel::{c_str, device::Core, devres::Devres, pci, prelude::*, sync::aref::ARef};
+use kernel::{c_str, device::Core, devres::Devres, io::Io, pci, prelude::*, sync::aref::ARef};
 
 struct Regs;
 
-- 
2.47.3

Re: [PATCH v3 1/5] rust: io: factor common I/O helpers into Io trait

[Alice Ryhl]

On Thu, Oct 30, 2025 at 03:48:38PM +0000, Zhi Wang wrote:
> The previous Io<SIZE> type combined both the generic I/O access helpers
> and MMIO implementation details in a single struct.
> 
> To establish a cleaner layering between the I/O interface and its concrete
> backends, paving the way for supporting additional I/O mechanisms in the
> future, Io<SIZE> need to be factored.
> 
> Factor the common helpers into a new Io trait, and move the MMIO-specific
> logic into a dedicated Mmio<SIZE> type implementing that trait. Rename the
> IoRaw to MmioRaw and update the bus MMIO implementations to use MmioRaw.
> 
> No functional change intended.
> 
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Bjorn Helgaas <helgaas@kernel.org>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Zhi Wang <zhiw@nvidia.com>

> +/// Represents a region of I/O space of a fixed size.
> +///
> +/// Provides common helpers for offset validation and address
> +/// calculation on top of a base address and maximum size.
> +///
> +/// Types implementing this trait (e.g. MMIO BARs or PCI config
> +/// regions) can share the same accessors.
> +pub trait Io<const SIZE: usize> {

I would consider moving SIZE to an associated constant.

	pub trait Io {
	    const MIN_SIZE: usize;
	
	    ...
	}

If it's a generic parameter, then the same type can implement both Io<5>
and Io<7> at the same time, but I don't think it makes sense for a
single type to implement Io with different minimum sizes.

>      /// Returns the base address of this mapping.
> -    #[inline]
> -    pub fn addr(&self) -> usize {
> -        self.0.addr()
> -    }
> +    fn addr(&self) -> usize;
>  
>      /// Returns the maximum size of this mapping.
> -    #[inline]
> -    pub fn maxsize(&self) -> usize {
> -        self.0.maxsize()
> -    }
> -
> -    #[inline]
> -    const fn offset_valid<U>(offset: usize, size: usize) -> bool {
> -        let type_size = core::mem::size_of::<U>();
> -        if let Some(end) = offset.checked_add(type_size) {
> -            end <= size && offset % type_size == 0
> -        } else {
> -            false
> -        }
> -    }
> +    fn maxsize(&self) -> usize;
>  
> +    /// Returns the absolute I/O address for a given `offset`.
> +    /// Performs runtime bounds checks using [`offset_valid`]
>      #[inline]
>      fn io_addr<U>(&self, offset: usize) -> Result<usize> {
> -        if !Self::offset_valid::<U>(offset, self.maxsize()) {
> +        if !offset_valid::<U>(offset, self.maxsize()) {
>              return Err(EINVAL);
>          }
>  
> @@ -217,50 +215,197 @@ fn io_addr<U>(&self, offset: usize) -> Result<usize> {
>          self.addr().checked_add(offset).ok_or(EINVAL)
>      }
>  
> +    /// Returns the absolute I/O address for a given `offset`,
> +    /// performing compile-time bound checks.
>      #[inline]
>      fn io_addr_assert<U>(&self, offset: usize) -> usize {
> -        build_assert!(Self::offset_valid::<U>(offset, SIZE));
> +        build_assert!(offset_valid::<U>(offset, SIZE));
>  
>          self.addr() + offset
>      }
>  
> -    define_read!(read8, try_read8, readb -> u8);
> -    define_read!(read16, try_read16, readw -> u16);
> -    define_read!(read32, try_read32, readl -> u32);
> +    /// Infallible 8-bit read with compile-time bounds check.
> +    fn read8(&self, _offset: usize) -> u8 {
> +        !0
> +    }
> +
> +    /// Infallible 16-bit read with compile-time bounds check.
> +    fn read16(&self, _offset: usize) -> u16 {
> +        !0
> +    }
> +
> +    /// Infallible 32-bit read with compile-time bounds check.
> +    fn read32(&self, _offset: usize) -> u32 {
> +        !0
> +    }
> +
> +    /// Infallible 64-bit read with compile-time bounds check (64-bit only).
> +    #[cfg(CONFIG_64BIT)]
> +    fn read64(&self, _offset: usize) -> u64 {
> +        !0
> +    }
> +
> +    /// Fallible 8-bit read with runtime bounds check.
> +    fn try_read8(&self, _offset: usize) -> Result<u8> {
> +        Err(ENOTSUPP)
> +    }
> +
> +    /// Fallible 16-bit read with runtime bounds check.
> +    fn try_read16(&self, _offset: usize) -> Result<u16> {
> +        Err(ENOTSUPP)
> +    }
> +
> +    /// Fallible 32-bit read with runtime bounds check.
> +    fn try_read32(&self, _offset: usize) -> Result<u32> {
> +        Err(ENOTSUPP)
> +    }
> +
> +    /// Fallible 64-bit read with runtime bounds check (64-bit only).
> +    #[cfg(CONFIG_64BIT)]
> +    fn try_read64(&self, _offset: usize) -> Result<u64> {
> +        Err(ENOTSUPP)
> +    }
> +
> +    /// Infallible 8-bit write with compile-time bounds check.
> +    fn write8(&self, _value: u8, _offset: usize) {
> +        ()
> +    }
> +
> +    /// Infallible 16-bit write with compile-time bounds check.
> +    fn write16(&self, _value: u16, _offset: usize) {
> +        ()
> +    }
> +
> +    /// Infallible 32-bit write with compile-time bounds check.
> +    fn write32(&self, _value: u32, _offset: usize) {
> +        ()
> +    }
> +
> +    /// Infallible 64-bit write with compile-time bounds check (64-bit only).
> +    #[cfg(CONFIG_64BIT)]
> +    fn write64(&self, _value: u64, _offset: usize) {
> +        ()
> +    }
> +
> +    /// Fallible 8-bit write with runtime bounds check.
> +    fn try_write8(&self, value: u8, offset: usize) -> Result;
> +
> +    /// Fallible 16-bit write with runtime bounds check.
> +    fn try_write16(&self, value: u16, offset: usize) -> Result;
> +
> +    /// Fallible 32-bit write with runtime bounds check.
> +    fn try_write32(&self, value: u32, offset: usize) -> Result;
> +
> +    /// Fallible 64-bit write with runtime bounds check (64-bit only).
> +    #[cfg(CONFIG_64BIT)]
> +    fn try_write64(&self, _value: u64, _offset: usize) -> Result {
> +        Err(ENOTSUPP)
> +    }

Why are there default implementations for all of these trait methods? I
would suggest not providing any default implementations at all.

Alice

Re: [PATCH v3 1/5] rust: io: factor common I/O helpers into Io trait

[Zhi Wang]

On Fri, 31 Oct 2025 09:07:04 +0000
Alice Ryhl <aliceryhl@google.com> wrote:

> On Thu, Oct 30, 2025 at 03:48:38PM +0000, Zhi Wang wrote:
> > The previous Io<SIZE> type combined both the generic I/O access
> > helpers and MMIO implementation details in a single struct.
> > 
> > To establish a cleaner layering between the I/O interface and its
> > concrete backends, paving the way for supporting additional I/O
> > mechanisms in the future, Io<SIZE> need to be factored.
> > 
> > Factor the common helpers into a new Io trait, and move the
> > MMIO-specific logic into a dedicated Mmio<SIZE> type implementing
> > that trait. Rename the IoRaw to MmioRaw and update the bus MMIO
> > implementations to use MmioRaw.
> > 
> > No functional change intended.
> > 
> > Cc: Alexandre Courbot <acourbot@nvidia.com>
> > Cc: Bjorn Helgaas <helgaas@kernel.org>
> > Cc: Danilo Krummrich <dakr@kernel.org>
> > Cc: John Hubbard <jhubbard@nvidia.com>
> > Signed-off-by: Zhi Wang <zhiw@nvidia.com>
> 
> > +/// Represents a region of I/O space of a fixed size.
> > +///
> > +/// Provides common helpers for offset validation and address
> > +/// calculation on top of a base address and maximum size.
> > +///
> > +/// Types implementing this trait (e.g. MMIO BARs or PCI config
> > +/// regions) can share the same accessors.
> > +pub trait Io<const SIZE: usize> {
> 
> I would consider moving SIZE to an associated constant.
> 
> 	pub trait Io {
> 	    const MIN_SIZE: usize;
> 	
> 	    ...
> 	}
> 
> If it's a generic parameter, then the same type can implement both
> Io<5> and Io<7> at the same time, but I don't think it makes sense
> for a single type to implement Io with different minimum sizes.
> 

I see your point. It also makes the code look cleaner.
From my understanding, this is essentially a choice between performing
static boundary checks through the type system using const generics, or
using build_assert!() with a trait or struct-associated constant.

Let me take a closer look and experiment a bit with it. :)

> >      /// Returns the base address of this mapping.
> > -    #[inline]
...ditto
> > +    /// Infallible 64-bit write with compile-time bounds check
> > (64-bit only).
> > +    #[cfg(CONFIG_64BIT)]
> > +    fn write64(&self, _value: u64, _offset: usize) {
> > +        ()
> > +    }
> > +
> > +    /// Fallible 8-bit write with runtime bounds check.
> > +    fn try_write8(&self, value: u8, offset: usize) -> Result;
> > +
> > +    /// Fallible 16-bit write with runtime bounds check.
> > +    fn try_write16(&self, value: u16, offset: usize) -> Result;
> > +
> > +    /// Fallible 32-bit write with runtime bounds check.
> > +    fn try_write32(&self, value: u32, offset: usize) -> Result;
> > +
> > +    /// Fallible 64-bit write with runtime bounds check (64-bit
> > only).
> > +    #[cfg(CONFIG_64BIT)]
> > +    fn try_write64(&self, _value: u64, _offset: usize) -> Result {
> > +        Err(ENOTSUPP)
> > +    }
> 
> Why are there default implementations for all of these trait methods?
> I would suggest not providing any default implementations at all.
> 

Yeah, I actually tried that in an earlier version.
I noticed that each backend is a bit different — for example, the PCI
config space routines don’t have read64()/write64() either. By
design, we don’t provide infallible versions for the PCI config space
backend (unlike the MMIO one). Other backends might have similar cases
as well.

So I ended up keeping the trait’s default implementation "minimal", only
including the methods every backend really has to implement. The default
impls are mainly there to catch situations where a driver calls something
it shouldn’t.

I should probably make the compiler complain when an infallible op isn’t
supported by a given backend. And if you have any ideas on making this
more elegant, I’m all ears. :)

Z.

> Alice

Re: [PATCH v3 1/5] rust: io: factor common I/O helpers into Io trait

[Danilo Krummrich]

On Fri Oct 31, 2025 at 1:48 PM CET, Zhi Wang wrote:
> Yeah, I actually tried that in an earlier version.
> I noticed that each backend is a bit different — for example, the PCI
> config space routines don’t have read64()/write64() either.

We can split it up in multiple traits if necessary, e.g. have a separate trait
for 64 bit operations.

> By
> design, we don’t provide infallible versions for the PCI config space
> backend (unlike the MMIO one). Other backends might have similar cases
> as well.

That seems wrong: For the PCI configuration space we can almost always do
infallibe range checks, i.e. the normal range is always guaranteed and extended
can be asserted as described in [1].

[1] https://lore.kernel.org/lkml/DDWINZJUGVQ8.POKS7A6ZSRFK@kernel.org/

[PATCH v3 2/5] rust: io: factor out MMIO read/write macros

[Zhi Wang]

Refactor the existing MMIO accessors to use common call macros
instead of inlining the bindings calls in each `define_{read,write}!`
expansion.

This factoring separates the common offset/bounds checks from the
low-level call pattern, making it easier to add additional I/O accessor
families.

No functional change intended.

Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 rust/kernel/io.rs | 110 ++++++++++++++++++++++++++++++----------------
 1 file changed, 73 insertions(+), 37 deletions(-)

diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 0b48edabf39a..ded0f4ecf2ad 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -113,8 +113,34 @@ pub fn maxsize(&self) -> usize {
 #[repr(transparent)]
 pub struct Mmio<const SIZE: usize = 0>(MmioRaw<SIZE>);
 
+macro_rules! call_mmio_read {
+    (infallible, $c_fn:ident, $self:ident, $type:ty, $addr:expr) => {
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        unsafe { bindings::$c_fn($addr as *const c_void) as $type }
+    };
+
+    (fallible, $c_fn:ident, $self:ident, $type:ty, $addr:expr) => {{
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        Ok(unsafe { bindings::$c_fn($addr as *const c_void) as $type })
+    }};
+}
+
+macro_rules! call_mmio_write {
+    (infallible, $c_fn:ident, $self:ident, $ty:ty, $addr:expr, $value:expr) => {
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        unsafe { bindings::$c_fn($value, $addr as *mut c_void) }
+    };
+
+    (fallible, $c_fn:ident, $self:ident, $ty:ty, $addr:expr, $value:expr) => {{
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        unsafe { bindings::$c_fn($value, $addr as *mut c_void) };
+        Ok(())
+    }};
+}
+
 macro_rules! define_read {
-    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $c_fn:ident -> $type_name:ty) => {
+    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $call_macro:ident, $c_fn:ident ->
+     $type_name:ty) => {
         /// Read IO data from a given offset known at compile time.
         ///
         /// Bound checks are performed on compile time, hence if the offset is not known at compile
@@ -124,12 +150,13 @@ macro_rules! define_read {
         $vis fn $name(&self, offset: usize) -> $type_name {
             let addr = self.io_addr_assert::<$type_name>(offset);
 
-            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            unsafe { bindings::$c_fn(addr as *const c_void) }
+            // SAFETY: By the type invariant `addr` is a valid address for IO operations.
+            $call_macro!(infallible, $c_fn, self, $type_name, addr)
         }
     };
 
-    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $c_fn:ident -> $type_name:ty) => {
+    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $call_macro:ident, $c_fn:ident ->
+     $type_name:ty) => {
         /// Read IO data from a given offset.
         ///
         /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
@@ -138,14 +165,16 @@ macro_rules! define_read {
         $vis fn $try_name(&self, offset: usize) -> Result<$type_name> {
             let addr = self.io_addr::<$type_name>(offset)?;
 
-            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            Ok(unsafe { bindings::$c_fn(addr as *const c_void) })
+            // SAFETY: By the type invariant `addr` is a valid address for IO operations.
+            $call_macro!(fallible, $c_fn, self, $type_name, addr)
         }
     };
 }
+pub(crate) use define_read;
 
 macro_rules! define_write {
-    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $c_fn:ident <- $type_name:ty) => {
+    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $call_macro:ident, $c_fn:ident <-
+     $type_name:ty) => {
         /// Write IO data from a given offset known at compile time.
         ///
         /// Bound checks are performed on compile time, hence if the offset is not known at compile
@@ -155,12 +184,12 @@ macro_rules! define_write {
         $vis fn $name(&self, value: $type_name, offset: usize) {
             let addr = self.io_addr_assert::<$type_name>(offset);
 
-            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            unsafe { bindings::$c_fn(value, addr as *mut c_void) }
+            $call_macro!(infallible, $c_fn, self, $type_name, addr, value);
         }
     };
 
-    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $c_fn:ident <- $type_name:ty) => {
+    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $call_macro:ident, $c_fn:ident <-
+     $type_name:ty) => {
         /// Write IO data from a given offset.
         ///
         /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
@@ -169,12 +198,11 @@ macro_rules! define_write {
         $vis fn $try_name(&self, value: $type_name, offset: usize) -> Result {
             let addr = self.io_addr::<$type_name>(offset)?;
 
-            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            unsafe { bindings::$c_fn(value, addr as *mut c_void) }
-            Ok(())
+            $call_macro!(fallible, $c_fn, self, $type_name, addr, value)
         }
     };
 }
+pub(crate) use define_write;
 
 /// Checks whether an access of type `U` at the given `offset`
 /// is valid within this region.
@@ -316,43 +344,47 @@ fn maxsize(&self) -> usize {
         self.0.maxsize()
     }
 
-    define_read!(infallible, read8, readb -> u8);
-    define_read!(infallible, read16, readw -> u16);
-    define_read!(infallible, read32, readl -> u32);
+    define_read!(infallible, read8, call_mmio_read, readb -> u8);
+    define_read!(infallible, read16, call_mmio_read, readw -> u16);
+    define_read!(infallible, read32, call_mmio_read, readl -> u32);
     define_read!(
         infallible,
         #[cfg(CONFIG_64BIT)]
         read64,
+        call_mmio_read,
         readq -> u64
     );
 
-    define_read!(fallible, try_read8, readb -> u8);
-    define_read!(fallible, try_read16, readw -> u16);
-    define_read!(fallible, try_read32, readl -> u32);
+    define_read!(fallible, try_read8, call_mmio_read, readb -> u8);
+    define_read!(fallible, try_read16, call_mmio_read, readw -> u16);
+    define_read!(fallible, try_read32, call_mmio_read, readl -> u32);
     define_read!(
         fallible,
         #[cfg(CONFIG_64BIT)]
         try_read64,
+        call_mmio_read,
         readq -> u64
     );
 
-    define_write!(infallible, write8, writeb <- u8);
-    define_write!(infallible, write16, writew <- u16);
-    define_write!(infallible, write32, writel <- u32);
+    define_write!(infallible, write8, call_mmio_write, writeb <- u8);
+    define_write!(infallible, write16, call_mmio_write, writew <- u16);
+    define_write!(infallible, write32, call_mmio_write, writel <- u32);
     define_write!(
         infallible,
         #[cfg(CONFIG_64BIT)]
         write64,
+        call_mmio_write,
         writeq <- u64
     );
 
-    define_write!(fallible, try_write8, writeb <- u8);
-    define_write!(fallible, try_write16, writew <- u16);
-    define_write!(fallible, try_write32, writel <- u32);
+    define_write!(fallible, try_write8, call_mmio_write, writeb <- u8);
+    define_write!(fallible, try_write16, call_mmio_write, writew <- u16);
+    define_write!(fallible, try_write32, call_mmio_write, writel <- u32);
     define_write!(
         fallible,
         #[cfg(CONFIG_64BIT)]
         try_write64,
+        call_mmio_write,
         writeq <- u64
     );
 }
@@ -369,43 +401,47 @@ pub unsafe fn from_raw(raw: &MmioRaw<SIZE>) -> &Self {
         unsafe { &*core::ptr::from_ref(raw).cast() }
     }
 
-    define_read!(infallible, pub read8_relaxed, readb_relaxed -> u8);
-    define_read!(infallible, pub read16_relaxed, readw_relaxed -> u16);
-    define_read!(infallible, pub read32_relaxed, readl_relaxed -> u32);
+    define_read!(infallible, pub read8_relaxed, call_mmio_read, readb_relaxed -> u8);
+    define_read!(infallible, pub read16_relaxed, call_mmio_read, readw_relaxed -> u16);
+    define_read!(infallible, pub read32_relaxed, call_mmio_read, readl_relaxed -> u32);
     define_read!(
         infallible,
         #[cfg(CONFIG_64BIT)]
         pub read64_relaxed,
+        call_mmio_read,
         readq_relaxed -> u64
     );
 
-    define_read!(fallible, pub try_read8_relaxed, readb_relaxed -> u8);
-    define_read!(fallible, pub try_read16_relaxed, readw_relaxed -> u16);
-    define_read!(fallible, pub try_read32_relaxed, readl_relaxed -> u32);
+    define_read!(fallible, pub try_read8_relaxed, call_mmio_read, readb_relaxed -> u8);
+    define_read!(fallible, pub try_read16_relaxed, call_mmio_read, readw_relaxed -> u16);
+    define_read!(fallible, pub try_read32_relaxed, call_mmio_read, readl_relaxed -> u32);
     define_read!(
         fallible,
         #[cfg(CONFIG_64BIT)]
         pub try_read64_relaxed,
+        call_mmio_read,
         readq_relaxed -> u64
     );
 
-    define_write!(infallible, pub write8_relaxed, writeb_relaxed <- u8);
-    define_write!(infallible, pub write16_relaxed, writew_relaxed <- u16);
-    define_write!(infallible, pub write32_relaxed, writel_relaxed <- u32);
+    define_write!(infallible, pub write8_relaxed, call_mmio_write, writeb_relaxed <- u8);
+    define_write!(infallible, pub write16_relaxed, call_mmio_write, writew_relaxed <- u16);
+    define_write!(infallible, pub write32_relaxed, call_mmio_write, writel_relaxed <- u32);
     define_write!(
         infallible,
         #[cfg(CONFIG_64BIT)]
         pub write64_relaxed,
+        call_mmio_write,
         writeq_relaxed <- u64
     );
 
-    define_write!(fallible, pub try_write8_relaxed, writeb_relaxed <- u8);
-    define_write!(fallible, pub try_write16_relaxed, writew_relaxed <- u16);
-    define_write!(fallible, pub try_write32_relaxed, writel_relaxed <- u32);
+    define_write!(fallible, pub try_write8_relaxed, call_mmio_write, writeb_relaxed <- u8);
+    define_write!(fallible, pub try_write16_relaxed, call_mmio_write, writew_relaxed <- u16);
+    define_write!(fallible, pub try_write32_relaxed, call_mmio_write, writel_relaxed <- u32);
     define_write!(
         fallible,
         #[cfg(CONFIG_64BIT)]
         pub try_write64_relaxed,
+        call_mmio_write,
         writeq_relaxed <- u64
     );
 }
-- 
2.47.3

[PATCH v3 3/5] rust: pci: add a helper to query configuration space size

[Zhi Wang]

Expose a safe Rust wrapper for the `cfg_size` field of `struct pci_dev`,
allowing drivers to query the size of a device's configuration space.

This is useful for code that needs to know whether the device supports
extended configuration space (e.g. 256 vs 4096 bytes) when accessing PCI
configuration registers and apply runtime checks.

Cc: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 rust/kernel/pci.rs | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 77a8eb39ad32..9ebba8e08d2e 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -418,6 +418,19 @@ fn as_raw(&self) -> *mut bindings::pci_dev {
     }
 }
 
+/// Represents the size of a PCI configuration space.
+///
+/// PCI devices can have either a *normal* (legacy) configuration space of 256 bytes,
+/// or an *extended* configuration space of 4096 bytes as defined in the PCI Express
+/// specification.
+pub enum ConfigSpaceSize {
+    /// 256-byte legacy PCI configuration space.
+    Normal = 256,
+
+    /// 4096-byte PCIe extended configuration space.
+    Extended = 4096,
+}
+
 impl Device {
     /// Returns the PCI vendor ID as [`Vendor`].
     ///
@@ -514,6 +527,17 @@ pub fn pci_class(&self) -> Class {
         // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
         Class::from_raw(unsafe { (*self.as_raw()).class })
     }
+
+    /// Returns the size of configuration space.
+    pub fn cfg_size(&self) -> Result<ConfigSpaceSize> {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
+        let size = unsafe { (*self.as_raw()).cfg_size };
+        match size {
+            256 => Ok(ConfigSpaceSize::Normal),
+            4096 => Ok(ConfigSpaceSize::Extended),
+            _ => Err(EINVAL),
+        }
+    }
 }
 
 impl Device<device::Bound> {
-- 
2.47.3

Re: [PATCH v3 3/5] rust: pci: add a helper to query configuration space size

[Bjorn Helgaas]

On Thu, Oct 30, 2025 at 03:48:40PM +0000, Zhi Wang wrote:
> Expose a safe Rust wrapper for the `cfg_size` field of `struct pci_dev`,
> allowing drivers to query the size of a device's configuration space.
> 
> This is useful for code that needs to know whether the device supports
> extended configuration space (e.g. 256 vs 4096 bytes) when accessing PCI
> configuration registers and apply runtime checks.

What is the value of knowing the config space size, as opposed to just
having config space accessors return PCIBIOS_BAD_REGISTER_NUMBER or
similar when trying to read past the implemented size?

Apart from pci-sysfs and vfio, I don't really see any drivers that use
pdev->cfg_size today.

Re: [PATCH v3 3/5] rust: pci: add a helper to query configuration space size

[Zhi Wang]

On Thu, 30 Oct 2025 11:51:15 -0500
Bjorn Helgaas <helgaas@kernel.org> wrote:

> On Thu, Oct 30, 2025 at 03:48:40PM +0000, Zhi Wang wrote:
> > Expose a safe Rust wrapper for the `cfg_size` field of `struct
> > pci_dev`, allowing drivers to query the size of a device's
> > configuration space.
> > 
> > This is useful for code that needs to know whether the device
> > supports extended configuration space (e.g. 256 vs 4096 bytes) when
> > accessing PCI configuration registers and apply runtime checks.
> 
> What is the value of knowing the config space size, as opposed to just
> having config space accessors return PCIBIOS_BAD_REGISTER_NUMBER or
> similar when trying to read past the implemented size?
> 

Per my understading, the Io trait aims to provide a generic I/O
validation that can be reused across different transports -
MMIO, PCI, SPI, and others - with each backend implementing its own
region boundaries while sharing the same pre-access validation logic.

By design, the framework needs to know the valid address range
before performing the actual access. Without exposing
cfg_size(), we would have to add PCI configuration-specific
handling inside the framework.

> Apart from pci-sysfs and vfio, I don't really see any drivers that use
> pdev->cfg_size today.

It is for the framework so far. If we believe that driver doesn't need
this in the near term, I can make it private in the next re-spin.

Z.

Re: [PATCH v3 3/5] rust: pci: add a helper to query configuration space size

[Danilo Krummrich]

On Fri Oct 31, 2025 at 1:16 PM CET, Zhi Wang wrote:
> On Thu, 30 Oct 2025 11:51:15 -0500
> Bjorn Helgaas <helgaas@kernel.org> wrote:
>> Apart from pci-sysfs and vfio, I don't really see any drivers that use
>> pdev->cfg_size today.
>
> It is for the framework so far. If we believe that driver doesn't need
> this in the near term, I can make it private in the next re-spin.

Device::cfg_size() should indeed be private, I don't see a reason for drivers to
call this directly.

However, enum ConfigSpaceSize has to be public, such that we can implement a
method:

	pub fn config_space<'a, const SIZE: usize>(&'a self) -> Result<ConfigSpace<'a, SIZE>>

so the driver can assert whether it requires the normal or extended
configuration space size with e.g.:

	// Fails if the configuration space does not have an extended size.
	let cfg = pdev.config_space::<ConfigSpaceSize::Extended>()?;

Subsequently, we can do infallible accesses within the corresponding guaranteed
range.

Given that there are only two options, normal or extended, we can also drop the
const generic and just provide two separate methods:

	pub fn config_space<'a>(&'a self) -> Result<ConfigSpace<'a, ConfigSpaceSize::Normal>>

and

	pub fn config_space_extended<'a>(&'a self) -> Result<ConfigSpace<'a, ConfigSpaceSize::Extended>>

Allowing drivers to request a ConfigSpace<'a, 0> with only runtime checks makes
no sense, ConfigSpaceSize::Normal is always the minimum.

- Danilo

[PATCH v3 4/5] rust: pci: add config space read/write support

[Zhi Wang]

Introduce a `ConfigSpace` wrapper in Rust PCI abstraction to provide safe
accessors for PCI configuration space. The new type implements the
`Io` trait to share offset validation and bound-checking logic with
others.

Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 rust/kernel/pci.rs | 62 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 9ebba8e08d2e..80bf0d2420f3 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -10,7 +10,8 @@
     devres::Devres,
     driver,
     error::{from_result, to_result, Result},
-    io::{Mmio, MmioRaw},
+    io::{define_read, define_write},
+    io::{Io, Mmio, MmioRaw},
     irq::{self, IrqRequest},
     str::CStr,
     sync::aref::ARef,
@@ -305,6 +306,60 @@ pub struct Device<Ctx: device::DeviceContext = device::Normal>(
     PhantomData<Ctx>,
 );
 
+/// Represents the PCI configuration space of a device.
+///
+/// Provides typed read and write accessors for configuration registers
+/// using the standard `pci_read_config_*` and `pci_write_config_*` helpers.
+///
+/// The generic const parameter `SIZE` can be used to indicate the
+/// maximum size of the configuration space (e.g. 256 bytes for legacy,
+/// 4096 bytes for extended config space). The actual size is obtained
+/// from the underlying `struct pci_dev` via [`Device::cfg_size`].
+pub struct ConfigSpace<'a, const SIZE: usize = { ConfigSpaceSize::Extended as usize }> {
+    pdev: &'a Device<device::Core>,
+}
+
+macro_rules! call_config_read {
+    (fallible, $c_fn:ident, $self:ident, $ty:ty, $addr:expr) => {{
+        let mut val: $ty = 0;
+        let ret = unsafe { bindings::$c_fn($self.pdev.as_raw(), $addr as i32, &mut val) };
+        (ret == 0)
+            .then_some(Ok(val))
+            .unwrap_or_else(|| Err(Error::from_errno(ret)))
+    }};
+}
+
+macro_rules! call_config_write {
+    (fallible, $c_fn:ident, $self:ident, $ty:ty, $addr:expr, $value:expr) => {{
+        let ret = unsafe { bindings::$c_fn($self.pdev.as_raw(), $addr as i32, $value) };
+        (ret == 0)
+            .then_some(Ok(()))
+            .unwrap_or_else(|| Err(Error::from_errno(ret)))
+    }};
+}
+
+impl<'a, const SIZE: usize> Io<SIZE> for ConfigSpace<'a, SIZE> {
+    /// Returns the base address of this mapping.
+    #[inline]
+    fn addr(&self) -> usize {
+        0
+    }
+
+    /// Returns the maximum size of this mapping.
+    #[inline]
+    fn maxsize(&self) -> usize {
+        self.pdev.cfg_size().map_or(0, |v| v as usize)
+    }
+
+    define_read!(fallible, try_read8, call_config_read, pci_read_config_byte -> u8);
+    define_read!(fallible, try_read16, call_config_read, pci_read_config_word -> u16);
+    define_read!(fallible, try_read32, call_config_read, pci_read_config_dword -> u32);
+
+    define_write!(fallible, try_write8, call_config_write, pci_write_config_byte <- u8);
+    define_write!(fallible, try_write16, call_config_write, pci_write_config_word <- u16);
+    define_write!(fallible, try_write32, call_config_write, pci_write_config_dword <- u32);
+}
+
 /// A PCI BAR to perform I/O-Operations on.
 ///
 /// # Invariants
@@ -615,6 +670,11 @@ pub fn set_master(&self) {
         // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
         unsafe { bindings::pci_set_master(self.as_raw()) };
     }
+
+    /// Return an initialized config space object.
+    pub fn config_space<'a>(&'a self) -> Result<ConfigSpace<'a>> {
+        Ok(ConfigSpace { pdev: self })
+    }
 }
 
 // SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
-- 
2.47.3

Re: [PATCH v3 4/5] rust: pci: add config space read/write support

[Danilo Krummrich]

On Thu Oct 30, 2025 at 4:48 PM CET, Zhi Wang wrote:
> +impl<'a, const SIZE: usize> Io<SIZE> for ConfigSpace<'a, SIZE> {
> +    /// Returns the base address of this mapping.
> +    #[inline]
> +    fn addr(&self) -> usize {
> +        0
> +    }
> +
> +    /// Returns the maximum size of this mapping.
> +    #[inline]
> +    fn maxsize(&self) -> usize {
> +        self.pdev.cfg_size().map_or(0, |v| v as usize)
> +    }
> +
> +    define_read!(fallible, try_read8, call_config_read, pci_read_config_byte -> u8);
> +    define_read!(fallible, try_read16, call_config_read, pci_read_config_word -> u16);
> +    define_read!(fallible, try_read32, call_config_read, pci_read_config_dword -> u32);
> +
> +    define_write!(fallible, try_write8, call_config_write, pci_write_config_byte <- u8);
> +    define_write!(fallible, try_write16, call_config_write, pci_write_config_word <- u16);
> +    define_write!(fallible, try_write32, call_config_write, pci_write_config_dword <- u32);
> +}

Please also implement the infallible ones.

> +
>  /// A PCI BAR to perform I/O-Operations on.
>  ///
>  /// # Invariants
> @@ -615,6 +670,11 @@ pub fn set_master(&self) {
>          // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
>          unsafe { bindings::pci_set_master(self.as_raw()) };
>      }
> +
> +    /// Return an initialized config space object.
> +    pub fn config_space<'a>(&'a self) -> Result<ConfigSpace<'a>> {
> +        Ok(ConfigSpace { pdev: self })
> +    }

Please see [1].

[1] https://lore.kernel.org/lkml/DDWINZJUGVQ8.POKS7A6ZSRFK@kernel.org/

Re: [PATCH v3 4/5] rust: pci: add config space read/write support

[Zhi Wang]

On Fri, 31 Oct 2025 13:48:41 +0100
"Danilo Krummrich" <dakr@kernel.org> wrote:

> On Thu Oct 30, 2025 at 4:48 PM CET, Zhi Wang wrote:
> > +impl<'a, const SIZE: usize> Io<SIZE> for ConfigSpace<'a, SIZE> {
> > +    /// Returns the base address of this mapping.
> > +    #[inline]
> > +    fn addr(&self) -> usize {
> > +        0
> > +    }
> > +
> > +    /// Returns the maximum size of this mapping.
> > +    #[inline]
> > +    fn maxsize(&self) -> usize {
> > +        self.pdev.cfg_size().map_or(0, |v| v as usize)
> > +    }
> > +
> > +    define_read!(fallible, try_read8, call_config_read,
> > pci_read_config_byte -> u8);
> > +    define_read!(fallible, try_read16, call_config_read,
> > pci_read_config_word -> u16);
> > +    define_read!(fallible, try_read32, call_config_read,
> > pci_read_config_dword -> u32); +
> > +    define_write!(fallible, try_write8, call_config_write,
> > pci_write_config_byte <- u8);
> > +    define_write!(fallible, try_write16, call_config_write,
> > pci_write_config_word <- u16);
> > +    define_write!(fallible, try_write32, call_config_write,
> > pci_write_config_dword <- u32); +}
> 
> Please also implement the infallible ones.
> 

Thanks. Will do this in the next spin.

> > +
> >  /// A PCI BAR to perform I/O-Operations on.
> >  ///
> >  /// # Invariants
> > @@ -615,6 +670,11 @@ pub fn set_master(&self) {
> >          // SAFETY: `self.as_raw` is guaranteed to be a pointer to
> > a valid `struct pci_dev`. unsafe {
> > bindings::pci_set_master(self.as_raw()) }; }
> > +
> > +    /// Return an initialized config space object.
> > +    pub fn config_space<'a>(&'a self) -> Result<ConfigSpace<'a>> {
> > +        Ok(ConfigSpace { pdev: self })
> > +    }
> 
> Please see [1].
> 
> [1] https://lore.kernel.org/lkml/DDWINZJUGVQ8.POKS7A6ZSRFK@kernel.org/

[PATCH v3 5/5] sample: rust: pci: add tests for config space routines

[Zhi Wang]

Add tests exercising the PCI configuration space helpers.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 samples/rust/rust_driver_pci.rs | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/samples/rust/rust_driver_pci.rs b/samples/rust/rust_driver_pci.rs
index 528e672b6b89..f02ae6d089d0 100644
--- a/samples/rust/rust_driver_pci.rs
+++ b/samples/rust/rust_driver_pci.rs
@@ -58,6 +58,30 @@ fn testdev(index: &TestIndex, bar: &Bar0) -> Result<u32> {
 
         Ok(bar.read32(Regs::COUNT))
     }
+
+    fn config_space(pdev: &pci::Device<Core>) -> Result {
+        let config = pdev.config_space()?;
+
+        dev_info!(
+            pdev.as_ref(),
+            "pci-testdev config space try_read8 rev ID: {:x}\n",
+            config.try_read8(0x8)?
+        );
+
+        dev_info!(
+            pdev.as_ref(),
+            "pci-testdev config space try_read16 vendor ID: {:x}\n",
+            config.try_read16(0)?
+        );
+
+        dev_info!(
+            pdev.as_ref(),
+            "pci-testdev config space try_read32 BAR 0: {:x}\n",
+            config.try_read32(0x10)?
+        );
+
+        Ok(())
+    }
 }
 
 impl pci::Driver for SampleDriver {
@@ -93,6 +117,8 @@ fn probe(pdev: &pci::Device<Core>, info: &Self::IdInfo) -> Result<Pin<KBox<Self>
             Self::testdev(info, bar)?
         );
 
+        Self::config_space(pdev)?;
+
         Ok(drvdata)
     }
 
-- 
2.47.3

Re: [PATCH v3 5/5] sample: rust: pci: add tests for config space routines

[Danilo Krummrich]

On Thu Oct 30, 2025 at 4:48 PM CET, Zhi Wang wrote:
> +    fn config_space(pdev: &pci::Device<Core>) -> Result {
> +        let config = pdev.config_space()?;
> +
> +        dev_info!(
> +            pdev.as_ref(),
> +            "pci-testdev config space try_read8 rev ID: {:x}\n",
> +            config.try_read8(0x8)?
> +        );
> +
> +        dev_info!(
> +            pdev.as_ref(),
> +            "pci-testdev config space try_read16 vendor ID: {:x}\n",
> +            config.try_read16(0)?
> +        );
> +
> +        dev_info!(
> +            pdev.as_ref(),
> +            "pci-testdev config space try_read32 BAR 0: {:x}\n",
> +            config.try_read32(0x10)?
> +        );
> +
> +        Ok(())
> +    }
>  }

Please use the infallible accessors and add a TODO to use the register!() macro
for defining PCI configuration space registers once it has been move out of
nova-core.