> On 6 Jul 2026, at 09:44, Gary Guo <[email protected]> wrote:
>
> `Io` trait is now very easy to implement. Thus, implement it on `Bar` and
> `IoMem` directly and remove the `MmioOwned` struct.
>
> Reviewed-by: Alexandre Courbot <[email protected]>
> Signed-off-by: Gary Guo <[email protected]>
> ---
> rust/kernel/devres.rs | 12 +++---
> rust/kernel/io.rs | 103 +-------------------------------------------------
> rust/kernel/io/mem.rs | 26 +++++++------
> rust/kernel/pci/io.rs | 16 ++++----
> 4 files changed, 32 insertions(+), 125 deletions(-)
>
> diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
> index aed0c994fd30..3545ffc5345d 100644
> --- a/rust/kernel/devres.rs
> +++ b/rust/kernel/devres.rs
> @@ -68,8 +68,9 @@ struct Inner<T> {
> /// devres::Devres,
> /// io::{
> /// Io,
> -/// MmioOwned,
> +/// Mmio,
> /// MmioRaw,
> +/// MmioBackend,
> /// PhysAddr,
> /// Region, //
> /// },
> @@ -104,12 +105,13 @@ struct Inner<T> {
> /// }
> /// }
> ///
> -/// impl<const SIZE: usize> Deref for IoMem<SIZE> {
> -/// type Target = MmioOwned<SIZE>;
> +/// impl<'a, const SIZE: usize> Io<'a> for &'a IoMem<SIZE> {
> +/// type Backend = MmioBackend;
> +/// type Target = Region<SIZE>;
> ///
> -/// fn deref(&self) -> &Self::Target {
> +/// fn as_view(self) -> Mmio<'a, Region<SIZE>> {
> /// // SAFETY: The memory range stored in `self` has been properly
> mapped in `Self::new`.
> -/// unsafe { MmioOwned::from_raw(&self.0) }
> +/// unsafe { Mmio::from_raw(self.0) }
> /// }
> /// }
> /// # fn no_run(dev: &Device<Bound>) -> Result<(), Error> {
> diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
> index 89039b3defd5..c7533d605678 100644
> --- a/rust/kernel/io.rs
> +++ b/rust/kernel/io.rs
> @@ -98,8 +98,8 @@ fn size(p: *const Self) -> usize {
> /// the represented MMIO region does exist or is properly mapped.
> ///
> /// Instead, the bus specific MMIO implementation must convert this raw
> representation into an
> -/// `MmioOwned` instance providing the actual memory accessors. Only by the
> conversion into an
> -/// `MmioOwned` structure any guarantees are given.
> +/// `Mmio` instance providing the actual memory accessors. Only by the
> conversion into an `Mmio`
> +/// structure any guarantees are given.
> pub struct MmioRaw<T: ?Sized> {
> /// Pointer is in I/O address space.
> ///
> @@ -156,80 +156,6 @@ pub fn size(&self) -> usize {
> }
> }
>
> -/// IO-mapped memory region.
> -///
> -/// The creator (usually a subsystem / bus such as PCI) is responsible for
> creating the
> -/// mapping, performing an additional region request etc.
> -///
> -/// # Invariant
> -///
> -/// `addr` is the start and `maxsize` the length of valid I/O mapped memory
> region of size
> -/// `maxsize`.
> -///
> -/// # Examples
> -///
> -/// ```no_run
> -/// use kernel::{
> -/// bindings,
> -/// ffi::c_void,
> -/// io::{
> -/// Io,
> -/// MmioOwned,
> -/// MmioRaw,
> -/// PhysAddr,
> -/// Region,
> -/// },
> -/// };
> -/// use core::ops::Deref;
> -///
> -/// // See also `pci::Bar` for a real example.
> -/// struct IoMem<const SIZE: usize>(MmioRaw<Region<SIZE>>);
> -///
> -/// impl<const SIZE: usize> IoMem<SIZE> {
> -/// /// # Safety
> -/// ///
> -/// /// [`paddr`, `paddr` + `SIZE`) must be a valid MMIO region that is
> mappable into the CPUs
> -/// /// virtual address space.
> -/// unsafe fn new(paddr: usize) -> Result<Self>{
> -/// // SAFETY: By the safety requirements of this function [`paddr`,
> `paddr` + `SIZE`) is
> -/// // valid for `ioremap`.
> -/// let addr = unsafe { bindings::ioremap(paddr as PhysAddr, SIZE) };
> -/// if addr.is_null() {
> -/// return Err(ENOMEM);
> -/// }
> -///
> -/// Ok(IoMem(MmioRaw::new_region(addr as usize, SIZE)?))
> -/// }
> -/// }
> -///
> -/// impl<const SIZE: usize> Drop for IoMem<SIZE> {
> -/// fn drop(&mut self) {
> -/// // SAFETY: `self.0.addr()` is guaranteed to be properly mapped
> by `Self::new`.
> -/// unsafe { bindings::iounmap(self.0.addr() as *mut c_void); };
> -/// }
> -/// }
> -///
> -/// impl<const SIZE: usize> Deref for IoMem<SIZE> {
> -/// type Target = MmioOwned<SIZE>;
> -///
> -/// fn deref(&self) -> &Self::Target {
> -/// // SAFETY: The memory range stored in `self` has been properly
> mapped in `Self::new`.
> -/// unsafe { MmioOwned::from_raw(&self.0) }
> -/// }
> -/// }
> -///
> -///# fn no_run() -> Result<(), Error> {
> -/// // SAFETY: Invalid usage for example purposes.
> -/// let iomem = unsafe { IoMem::<{ core::mem::size_of::<u32>()
> }>::new(0xBAAAAAAD)? };
> -/// iomem.write32(0x42, 0x0);
> -/// assert!(iomem.try_write32(0x42, 0x0).is_ok());
> -/// assert!(iomem.try_write32(0x42, 0x4).is_err());
> -/// # Ok(())
> -/// # }
> -/// ```
> -#[repr(transparent)]
> -pub struct MmioOwned<const SIZE: usize = 0>(MmioRaw<Region<SIZE>>);
> -
> /// Checks whether an access of type `U` at the given `base` and the given
> `offset`
> /// is valid within this region.
> ///
> @@ -957,31 +883,6 @@ fn io_write(view: <$backend as IoBackend>::View<'_,
> $ty>, value: $ty) {
> #[cfg(CONFIG_64BIT)]
> impl_mmio_io_capable!(MmioBackend, u64, readq, writeq);
>
> -impl<'a, const SIZE: usize> Io<'a> for &'a MmioOwned<SIZE> {
> - type Backend = MmioBackend;
> - type Target = Region<SIZE>;
> -
> - #[inline]
> - fn as_view(self) -> Mmio<'a, Self::Target> {
> - // SAFETY: `Mmio` has same invariant as `MmioOwned`
> - unsafe { Mmio::from_raw(self.0) }
> - }
> -}
> -
> -impl<const SIZE: usize> MmioOwned<SIZE> {
> - /// Converts an `MmioRaw` into an `MmioOwned` 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<Region<SIZE>>) -> &Self {
> - // SAFETY: `MmioOwned` is a transparent wrapper around `MmioRaw`.
> - unsafe { &*core::ptr::from_ref(raw).cast() }
> - }
> -}
> -
> /// [`Mmio`] but using relaxed accessors.
> ///
> /// This type provides an implementation of [`Io`] that uses relaxed I/O MMIO
> operands instead of
> diff --git a/rust/kernel/io/mem.rs b/rust/kernel/io/mem.rs
> index 8f6c257c5b8e..d9b3189d09b4 100644
> --- a/rust/kernel/io/mem.rs
> +++ b/rust/kernel/io/mem.rs
> @@ -2,8 +2,6 @@
>
> //! Generic memory-mapped IO.
>
> -use core::ops::Deref;
> -
> use crate::{
> device::{
> Bound,
> @@ -16,7 +14,9 @@
> Region,
> Resource, //
> },
> - MmioOwned,
> + Io,
> + Mmio,
> + MmioBackend,
> MmioRaw, //
> },
> prelude::*,
> @@ -210,11 +210,13 @@ pub fn into_devres(self) ->
> Result<Devres<ExclusiveIoMem<'static, SIZE>>> {
> }
> }
>
> -impl<const SIZE: usize> Deref for ExclusiveIoMem<'_, SIZE> {
> - type Target = MmioOwned<SIZE>;
> +impl<'a, const SIZE: usize> Io<'a> for &'a ExclusiveIoMem<'_, SIZE> {
> + type Backend = MmioBackend;
> + type Target = super::Region<SIZE>;
>
> - fn deref(&self) -> &Self::Target {
> - &self.iomem
> + #[inline]
> + fn as_view(self) -> Mmio<'a, Self::Target> {
> + self.iomem.as_view()
> }
> }
>
> @@ -290,11 +292,13 @@ fn drop(&mut self) {
> }
> }
>
> -impl<const SIZE: usize> Deref for IoMem<'_, SIZE> {
> - type Target = MmioOwned<SIZE>;
> +impl<'a, const SIZE: usize> Io<'a> for &'a IoMem<'_, SIZE> {
> + type Backend = MmioBackend;
> + type Target = super::Region<SIZE>;
>
> - fn deref(&self) -> &Self::Target {
> + #[inline]
> + fn as_view(self) -> Mmio<'a, Self::Target> {
> // SAFETY: Safe as by the invariant of `IoMem`.
> - unsafe { MmioOwned::from_raw(&self.io) }
> + unsafe { Mmio::from_raw(self.io) }
> }
> }
> diff --git a/rust/kernel/pci/io.rs b/rust/kernel/pci/io.rs
> index e67c1e3694fb..4be33ecb4192 100644
> --- a/rust/kernel/pci/io.rs
> +++ b/rust/kernel/pci/io.rs
> @@ -11,16 +11,14 @@
> Io,
> IoBackend,
> IoCapable,
> - MmioOwned,
> + Mmio,
> + MmioBackend,
> MmioRaw,
> Region, //
> },
> prelude::*,
> ptr::KnownSize, //
> };
> -use core::{
> - ops::Deref, //
> -};
>
> /// Represents the size of a PCI configuration space.
> ///
> @@ -269,12 +267,14 @@ fn drop(&mut self) {
> }
> }
>
> -impl<const SIZE: usize> Deref for Bar<'_, SIZE> {
> - type Target = MmioOwned<SIZE>;
> +impl<'a, const SIZE: usize> Io<'a> for &'a Bar<'_, SIZE> {
> + type Backend = MmioBackend;
> + type Target = crate::io::Region<SIZE>;
>
> - fn deref(&self) -> &Self::Target {
> + #[inline]
> + fn as_view(self) -> Mmio<'a, Self::Target> {
> // SAFETY: By the type invariant of `Self`, the MMIO range in
> `self.io` is properly mapped.
> - unsafe { MmioOwned::from_raw(&self.io) }
> + unsafe { Mmio::from_raw(self.io) }
> }
> }
>
>
> --
> 2.54.0
>
>
Reviewed-by: Daniel Almeida <[email protected]>
