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Message-ID: <20260121205406.2e0c7e44.zhiw@nvidia.com>
Date: Wed, 21 Jan 2026 20:54:06 +0200
From: Zhi Wang <zhiw@...dia.com>
To: Gary Guo <gary@...yguo.net>
CC: <rust-for-linux@...r.kernel.org>, <linux-pci@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <dakr@...nel.org>, <aliceryhl@...gle.com>,
<bhelgaas@...gle.com>, <kwilczynski@...nel.org>, <ojeda@...nel.org>,
<alex.gaynor@...il.com>, <boqun.feng@...il.com>, <bjorn3_gh@...tonmail.com>,
<lossin@...nel.org>, <a.hindborg@...nel.org>, <tmgross@...ch.edu>,
<markus.probst@...teo.de>, <helgaas@...nel.org>, <cjia@...dia.com>,
<smitra@...dia.com>, <ankita@...dia.com>, <aniketa@...dia.com>,
<kwankhede@...dia.com>, <targupta@...dia.com>, <acourbot@...dia.com>,
<joelagnelf@...dia.com>, <jhubbard@...dia.com>, <zhiwang@...nel.org>,
<daniel.almeida@...labora.com>
Subject: Re: [PATCH v11 2/5] rust: io: separate generic I/O helpers from
MMIO implementation
On Wed, 21 Jan 2026 15:10:25 +0000
"Gary Guo" <gary@...yguo.net> wrote:
> On Wed Jan 21, 2026 at 2:23 PM GMT, Zhi Wang wrote:
> > The previous Io<SIZE> type combined both the generic I/O access helpers
> > and MMIO implementation details in a single struct. This coupling
> > prevented reusing the I/O helpers for other backends, such as PCI
> > configuration space.
> >
> > Establish a clean separation between the I/O interface and concrete
> > backends by separating generic I/O helpers from MMIO implementation.
> >
> > Introduce a new trait hierarchy to handle different access
> > capabilities:
> >
> > - IoCapable<T>: A marker trait indicating that a backend supports I/O
> > operations of a certain type (u8, u16, u32, or u64).
> >
> > - Io trait: Defines fallible I/O methods (try_read8, try_write8, etc.)
> > with runtime bounds checking.
> >
> > - IoKnownSize trait: Extends Io to define infallible I/O methods
> > (read8, write8, etc.) with compile-time bounds checking for regions
> > where the size is known at compile time.
> >
> > Move the MMIO-specific logic into a dedicated Mmio<SIZE> type that
> > implements the Io and IoKnownSize traits. Rename IoRaw to MmioRaw and
> > update consumers to use the new types.
> >
>
> Hi Zhi, thanks for doing the work. It looks much nicer now :)
>
Hey Gary. Glad to see that. :) Will address them in the next re-spin.
> Still, some comments below.
>
> Best,
> Gary
>
> > Cc: Alexandre Courbot <acourbot@...dia.com>
> > Cc: Alice Ryhl <aliceryhl@...gle.com>
> > Cc: Bjorn Helgaas <helgaas@...nel.org>
> > Cc: Gary Guo <gary@...yguo.net>
> > Cc: Danilo Krummrich <dakr@...nel.org>
> > Cc: John Hubbard <jhubbard@...dia.com>
> > Signed-off-by: Zhi Wang <zhiw@...dia.com>
> > ---
> > drivers/gpu/drm/tyr/regs.rs | 1 +
> > drivers/gpu/nova-core/gsp/sequencer.rs | 5 +-
> > drivers/gpu/nova-core/regs/macros.rs | 90 +++---
> > drivers/gpu/nova-core/vbios.rs | 1 +
> > drivers/pwm/pwm_th1520.rs | 5 +-
> > rust/kernel/devres.rs | 19 +-
> > rust/kernel/io.rs | 415 +++++++++++++++++++++----
> > rust/kernel/io/mem.rs | 16 +-
> > rust/kernel/io/poll.rs | 16 +-
> > rust/kernel/pci/io.rs | 12 +-
> > samples/rust/rust_driver_pci.rs | 4 +
> > 11 files changed, 453 insertions(+), 131 deletions(-)
> >
> > diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
> > index a97eb44a9a87..152afdcbaf78 100644
> > --- a/rust/kernel/io.rs
> > +++ b/rust/kernel/io.rs
> > @@ -32,16 +32,16 @@
> > /// 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);
> > @@ -81,14 +81,16 @@ pub fn maxsize(&self) -> usize {
> > /// ffi::c_void,
> > /// io::{
> > /// Io,
> > -/// IoRaw,
> > +/// IoKnownSize,
> > +/// Mmio,
> > +/// MmioRaw,
> > /// PhysAddr,
> > /// },
> > /// };
> > /// 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
> > @@ -103,7 +105,7 @@ pub fn maxsize(&self) -> usize {
> > /// return Err(ENOMEM);
> > /// }
> > ///
> > -/// Ok(IoMem(IoRaw::new(addr as usize, SIZE)?))
> > +/// Ok(IoMem(MmioRaw::new(addr as usize, SIZE)?))
> > /// }
> > /// }
> > ///
> > @@ -115,11 +117,11 @@ 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) }
> > /// }
> > /// }
> > ///
> > @@ -133,29 +135,31 @@ 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. @@ -163,74 +167,95 @@ pub fn
> > $try_name(&self, offset: usize) -> Result<$type_name> { }
> > };
> > }
> > +pub(crate) use define_read;
> >
> > 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.
> > - unsafe { bindings::$c_fn(value, addr as *mut c_void) }
> > + unsafe { bindings::$c_fn(value, addr as *mut c_void) };
> > Ok(())
> > }
> > };
> > }
> > -
> > -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() }
> > +pub(crate) use define_write;
> > +
> > +/// 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
> > }
> > +}
> > +
> > +/// Marker trait indicating that an I/O backend supports operations
> > of a certain type. +///
> > +/// Different I/O backends can implement this trait to expose only
> > the operations they support. +///
> > +/// For example, a PCI configuration space may implement
> > `IoCapable<u8>`, `IoCapable<u16>`, +/// and `IoCapable<u32>`, but not
> > `IoCapable<u64>`, while an MMIO region on a 64-bit +/// system might
> > implement all four. +pub trait IoCapable<T> {}
> > +
> > +/// Types implementing this trait (e.g. MMIO BARs or PCI config
> > regions) +/// can perform I/O operations on regions of memory.
> > +///
> > +/// This is an abstract representation to be implemented by arbitrary
> > I/O +/// backends (e.g. MMIO, PCI config space, etc.).
> > +///
> > +/// The [`Io`] trait provides:
> > +/// - Base address and size information
> > +/// - Helper methods for offset validation and address calculation
> > +/// - Fallible (runtime checked) accessors for different data widths
> > +///
> > +/// Which I/O methods are available depends on which [`IoCapable<T>`]
> > traits +/// are implemented for the type.
> > +///
> > +/// # Examples
> > +///
> > +/// For MMIO regions, all widths (u8, u16, u32, and u64 on 64-bit
> > systems) are typically +/// supported. For PCI configuration space,
> > u8, u16, and u32 are supported but u64 is not. +pub trait Io {
> > + /// Minimum usable size of this region.
> > + const MIN_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`,
> > + /// performing runtime bound checks.
> > #[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);
> > }
> >
> > @@ -239,50 +264,302 @@ 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, Self::MIN_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);
> > + /// Fallible 8-bit read with runtime bounds check.
> > + #[inline(always)]
> > + fn try_read8(&self, _offset: usize) -> Result<u8>
> > + where
> > + Self: IoCapable<u8>,
> > + {
> > + const { assert!(false, "Backend does not support fallible
> > 8-bit read") };
> > + unreachable!()
>
> I think this is actually where `build_error!()` make sense. Similar to
> how we use it for vtable methods that are not defined (and hence will be
> `None`).
>
> This would eliminate `unreachable!()`.
>
> > + }
> > +
> > + /// Fallible 16-bit read with runtime bounds check.
> > + #[inline(always)]
> > + fn try_read16(&self, _offset: usize) -> Result<u16>
> > + where
> > + Self: IoCapable<u16>,
> > + {
> > + const { assert!(false, "Backend does not support fallible
> > 16-bit read") };
> > + unreachable!()
> > + }
> > +
> > + /// Fallible 32-bit read with runtime bounds check.
> > + #[inline(always)]
> > + fn try_read32(&self, _offset: usize) -> Result<u32>
> > + where
> > + Self: IoCapable<u32>,
> > + {
> > + const { assert!(false, "Backend does not support fallible
> > 32-bit read") };
> > + unreachable!()
> > + }
> > +
> > + /// Fallible 64-bit read with runtime bounds check.
> > + #[cfg(CONFIG_64BIT)]
> > + #[inline(always)]
> > + fn try_read64(&self, _offset: usize) -> Result<u64>
> > + where
> > + Self: IoCapable<u64>,
> > + {
> > + const { assert!(false, "Backend does not support fallible
> > 64-bit read") };
> > + unreachable!()
> > + }
> > +
> > + /// Fallible 8-bit write with runtime bounds check.
> > + #[inline(always)]
> > + fn try_write8(&self, _value: u8, _offset: usize) -> Result
> > + where
> > + Self: IoCapable<u8>,
> > + {
> > + const { assert!(false, "Backend does not support fallible
> > 8-bit write") };
> > + unreachable!()
> > + }
> > +
> > + /// Fallible 16-bit write with runtime bounds check.
> > + #[inline(always)]
> > + fn try_write16(&self, _value: u16, _offset: usize) -> Result
> > + where
> > + Self: IoCapable<u16>,
> > + {
> > + const { assert!(false, "Backend does not support fallible
> > 16-bit write") };
> > + unreachable!()
> > + }
> > +
> > + /// Fallible 32-bit write with runtime bounds check.
> > + #[inline(always)]
> > + fn try_write32(&self, _value: u32, _offset: usize) -> Result
> > + where
> > + Self: IoCapable<u32>,
> > + {
> > + const { assert!(false, "Backend does not support fallible
> > 32-bit write") };
> > + unreachable!()
> > + }
> > +
> > + /// Fallible 64-bit write with runtime bounds check.
> > + #[cfg(CONFIG_64BIT)]
>
> As Alice mentioned previously, the CONFIG_64BIT shouldn't need to exist
> on the trait.
>
> The cfg on the impl is sufficient (there might be `Io` that provides
> 64-bit access on 32-bit systems anyway).
>
> > + #[inline(always)]
> > + fn try_write64(&self, _value: u64, _offset: usize) -> Result
> > + where
> > + Self: IoCapable<u64>,
> > + {
> > + const { assert!(false, "Backend does not support fallible
> > 64-bit write") };
> > + unreachable!()
> > + }
> > +}
> > +
> > +/// Types with a known size at compile time can provide infallible
> > I/O accessors. +///
> > +/// This trait extends [`Io`] to provide compile-time bounds-checked
> > I/O operations +/// for regions where the size is known at compile
> > time (e.g., `Mmio<SIZE>`). +pub trait IoKnownSize: Io {
> > + /// Infallible 8-bit read with compile-time bounds check.
> > + #[inline(always)]
> > + fn read8(&self, _offset: usize) -> u8
> > + where
> > + Self: IoCapable<u8>,
>
> I think these *can* be also on `Io` with `Self: IoKnownSize` bound,
> although in practice I don't think it would matter.
>
> > + {
> > + const { assert!(false, "Backend does not support infallible
> > 8-bit read") };
> > + unreachable!()
> > + }
> > +
> > + /// Infallible 16-bit read with compile-time bounds check.
> > + #[inline(always)]
> > + fn read16(&self, _offset: usize) -> u16
> > + where
> > + Self: IoCapable<u16>,
> > + {
> > + const { assert!(false, "Backend does not support infallible
> > 16-bit read") };
> > + unreachable!()
> > + }
> > +
> > + /// Infallible 32-bit read with compile-time bounds check.
> > + #[inline(always)]
> > + fn read32(&self, _offset: usize) -> u32
> > + where
> > + Self: IoCapable<u32>,
> > + {
> > + const { assert!(false, "Backend does not support infallible
> > 32-bit read") };
> > + unreachable!()
> > + }
> > +
> > + /// Infallible 64-bit read with compile-time bounds check.
> > + #[cfg(CONFIG_64BIT)]
> > + #[inline(always)]
> > + fn read64(&self, _offset: usize) -> u64
> > + where
> > + Self: IoCapable<u64>,
> > + {
> > + const { assert!(false, "Backend does not support infallible
> > 64-bit read") };
> > + unreachable!()
> > + }
> > +
> > + /// Infallible 8-bit write with compile-time bounds check.
> > + #[inline(always)]
> > + fn write8(&self, _value: u8, _offset: usize)
> > + where
> > + Self: IoCapable<u8>,
> > + {
> > + const { assert!(false, "Backend does not support infallible
> > 8-bit write") };
> > + unreachable!()
> > + }
> > +
> > + /// Infallible 16-bit write with compile-time bounds check.
> > + #[inline(always)]
> > + fn write16(&self, _value: u16, _offset: usize)
> > + where
> > + Self: IoCapable<u16>,
> > + {
> > + const { assert!(false, "Backend does not support infallible
> > 16-bit write") };
> > + unreachable!()
> > + }
> > +
> > + /// Infallible 32-bit write with compile-time bounds check.
> > + #[inline(always)]
> > + fn write32(&self, _value: u32, _offset: usize)
> > + where
> > + Self: IoCapable<u32>,
> > + {
> > + const { assert!(false, "Backend does not support infallible
> > 32-bit write") };
> > + unreachable!()
> > + }
> > +
> > + /// Infallible 64-bit write with compile-time bounds check.
> > + #[cfg(CONFIG_64BIT)]
> > + #[inline(always)]
> > + fn write64(&self, _value: u64, _offset: usize)
> > + where
> > + Self: IoCapable<u64>,
> > + {
> > + const { assert!(false, "Backend does not support infallible
> > 64-bit write") };
> > + unreachable!()
> > + }
> > +}
> > +
> > +// MMIO regions support 8, 16, and 32-bit accesses.
> > +impl<const SIZE: usize> IoCapable<u8> for Mmio<SIZE> {}
> > +impl<const SIZE: usize> IoCapable<u16> for Mmio<SIZE> {}
> > +impl<const SIZE: usize> IoCapable<u32> for Mmio<SIZE> {}
> > +
> > +// MMIO regions on 64-bit systems also support 64-bit accesses.
> > +#[cfg(CONFIG_64BIT)]
> > +impl<const SIZE: usize> IoCapable<u64> for Mmio<SIZE> {}
> > +
> > +impl<const SIZE: usize> Io for Mmio<SIZE> {
> > + const MIN_SIZE: usize = 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!(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,
> > 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_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> IoKnownSize for Mmio<SIZE> {
> > + 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_relaxed,
> > - try_read64_relaxed,
> > - readq_relaxed -> u64
> > + 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,
> > - 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 e4878c131c6d..620022cff401 100644
> > --- a/rust/kernel/io/mem.rs
> > +++ b/rust/kernel/io/mem.rs
> > @@ -16,8 +16,8 @@
> > Region,
> > Resource, //
> > },
> > - Io,
> > - IoRaw, //
> > + Mmio,
> > + MmioRaw, //
> > },
> > prelude::*,
> > };
> > @@ -212,7 +212,7 @@ 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
> > @@ -226,10 +226,10 @@ 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> {
> > @@ -264,7 +264,7 @@ 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)
> > @@ -287,10 +287,10 @@ 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 b1a2570364f4..75d1b3e8596c 100644
> > --- a/rust/kernel/io/poll.rs
> > +++ b/rust/kernel/io/poll.rs
> > @@ -45,12 +45,16 @@
> > /// # 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 { /// read_poll_timeout(
> > /// // The `op` closure reads the value of a specific status
> > register. /// || io.try_read16(0x1000),
> > @@ -128,12 +132,16 @@ pub fn read_poll_timeout<Op, Cond, T>(
> > /// # Examples
> > ///
> > /// ```no_run
> > -/// use kernel::io::{poll::read_poll_timeout_atomic, Io};
> > +/// use kernel::io::{
> > +/// Io,
> > +/// Mmio,
> > +/// poll::read_poll_timeout_atomic, //
> > +/// };
> > /// 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 { /// read_poll_timeout_atomic(
> > /// // The `op` closure reads the value of a specific status
> > register. /// || io.try_read16(0x1000),
> > diff --git a/rust/kernel/pci/io.rs b/rust/kernel/pci/io.rs
> > index 70e3854e7d8d..e3377397666e 100644
> > --- a/rust/kernel/pci/io.rs
> > +++ b/rust/kernel/pci/io.rs
> > @@ -8,8 +8,8 @@
> > device,
> > devres::Devres,
> > io::{
> > - Io,
> > - IoRaw, //
> > + Mmio,
> > + MmioRaw, //
> > },
> > prelude::*,
> > sync::aref::ARef, //
> > @@ -27,7 +27,7 @@
> > /// 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,
> > }
> >
> > @@ -63,7 +63,7 @@ pub(super) 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:
> > @@ -117,11 +117,11 @@ 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 ef04c6401e6a..bfb053059667
> > 100644 --- a/samples/rust/rust_driver_pci.rs
> > +++ b/samples/rust/rust_driver_pci.rs
> > @@ -7,6 +7,10 @@
> > use kernel::{
> > device::Core,
> > devres::Devres,
> > + io::{
> > + Io,
> > + IoKnownSize, //
> > + },
> > pci,
> > prelude::*,
> > sync::aref::ARef, //
>
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