> On 6 Jul 2026, at 09:44, Gary Guo <[email protected]> wrote:
>
> Currently, `Io` is implemented on owned I/O objects (e.g. `Bar`). This is
> going to change with I/O projections, as then `Io` needs to work both for
> owned objects and views of them. Views are themselves reference-like
> (however they obviously cannot be references, because they belong to a
> different address space).
>
> To facilitate the change, change `Io` to be implemented on reference types
> for the owned I/O objects, and make methods take `self` instead of `&self`.
> When I/O views are implemented, we can then naturally implement `Io` for
> these objects.
>
> Reviewed-by: Alexandre Courbot <[email protected]>
> Signed-off-by: Gary Guo <[email protected]>
> ---
> rust/kernel/io.rs | 82 ++++++++++++++++++++++++++-------------------------
> rust/kernel/pci/io.rs | 12 ++++----
> 2 files changed, 48 insertions(+), 46 deletions(-)
>
> diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
> index 87141eb07056..9f060dd29182 100644
> --- a/rust/kernel/io.rs
> +++ b/rust/kernel/io.rs
> @@ -223,7 +223,7 @@ pub trait IoCapable<T> {
> ///
> /// - The range `[address..address + size_of::<T>()]` must be within the
> bounds of `Self`.
> /// - `address` must be aligned.
> - unsafe fn io_read(&self, address: usize) -> T;
> + unsafe fn io_read(self, address: usize) -> T;
>
> /// Performs an I/O write of `value` at `address`.
> ///
> @@ -231,7 +231,7 @@ pub trait IoCapable<T> {
> ///
> /// - The range `[address..address + size_of::<T>()]` must be within the
> bounds of `Self`.
> /// - `address` must be aligned.
> - unsafe fn io_write(&self, value: T, address: usize);
> + unsafe fn io_write(self, value: T, address: usize);
> }
>
> /// Describes a given I/O location: its offset, width, and type to convert
> the raw value from and
> @@ -294,25 +294,27 @@ fn offset(self) -> usize {
> /// Which I/O methods are available depends on which [`IoCapable<T>`] traits
> /// are implemented for the type.
> ///
> +/// This should be implemented on cheaply copyable handles, such as
> references or view types.
> +///
> /// # 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 {
> +pub trait Io: Copy {
> /// Type of this I/O region. For untyped regions, [`Region`] can be used.
> type Target: ?Sized + KnownSize;
>
> /// Returns the base address of this mapping.
> - fn addr(&self) -> usize;
> + fn addr(self) -> usize;
>
> /// Returns the maximum size of this mapping.
> - fn maxsize(&self) -> usize;
> + fn maxsize(self) -> usize;
>
> /// Returns the absolute I/O address for a given `offset`,
> /// performing compile-time bound checks.
> // Always inline to optimize out error path of `build_assert`.
> #[inline(always)]
> - fn io_addr_assert<U>(&self, offset: usize) -> usize {
> + fn io_addr_assert<U>(self, offset: usize) -> usize {
> // We cannot check alignment with `offset_valid` using `self.addr()`.
> So set 0 for it and
> // ensure alignment by checking that the alignment of `U` is smaller
> or equal to the
> // alignment of `Self::Target`.
> @@ -325,7 +327,7 @@ fn io_addr_assert<U>(&self, offset: usize) -> 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> {
> + fn io_addr<U>(self, offset: usize) -> Result<usize> {
> if !offset_valid::<U>(self.addr(), offset, self.maxsize()) {
> return Err(EINVAL);
> }
> @@ -337,7 +339,7 @@ fn io_addr<U>(&self, offset: usize) -> Result<usize> {
>
> /// Fallible 8-bit read with runtime bounds check.
> #[inline(always)]
> - fn try_read8(&self, offset: usize) -> Result<u8>
> + fn try_read8(self, offset: usize) -> Result<u8>
> where
> usize: IoLoc<Self::Target, u8, IoType = u8>,
> Self: IoCapable<u8>,
> @@ -347,7 +349,7 @@ fn try_read8(&self, offset: usize) -> Result<u8>
>
> /// Fallible 16-bit read with runtime bounds check.
> #[inline(always)]
> - fn try_read16(&self, offset: usize) -> Result<u16>
> + fn try_read16(self, offset: usize) -> Result<u16>
> where
> usize: IoLoc<Self::Target, u16, IoType = u16>,
> Self: IoCapable<u16>,
> @@ -357,7 +359,7 @@ fn try_read16(&self, offset: usize) -> Result<u16>
>
> /// Fallible 32-bit read with runtime bounds check.
> #[inline(always)]
> - fn try_read32(&self, offset: usize) -> Result<u32>
> + fn try_read32(self, offset: usize) -> Result<u32>
> where
> usize: IoLoc<Self::Target, u32, IoType = u32>,
> Self: IoCapable<u32>,
> @@ -367,7 +369,7 @@ fn try_read32(&self, offset: usize) -> Result<u32>
>
> /// Fallible 64-bit read with runtime bounds check.
> #[inline(always)]
> - fn try_read64(&self, offset: usize) -> Result<u64>
> + fn try_read64(self, offset: usize) -> Result<u64>
> where
> usize: IoLoc<Self::Target, u64, IoType = u64>,
> Self: IoCapable<u64>,
> @@ -377,7 +379,7 @@ fn try_read64(&self, offset: usize) -> Result<u64>
>
> /// Fallible 8-bit write with runtime bounds check.
> #[inline(always)]
> - fn try_write8(&self, value: u8, offset: usize) -> Result
> + fn try_write8(self, value: u8, offset: usize) -> Result
> where
> usize: IoLoc<Self::Target, u8, IoType = u8>,
> Self: IoCapable<u8>,
> @@ -387,7 +389,7 @@ fn try_write8(&self, value: u8, offset: usize) -> Result
>
> /// Fallible 16-bit write with runtime bounds check.
> #[inline(always)]
> - fn try_write16(&self, value: u16, offset: usize) -> Result
> + fn try_write16(self, value: u16, offset: usize) -> Result
> where
> usize: IoLoc<Self::Target, u16, IoType = u16>,
> Self: IoCapable<u16>,
> @@ -397,7 +399,7 @@ fn try_write16(&self, value: u16, offset: usize) -> Result
>
> /// Fallible 32-bit write with runtime bounds check.
> #[inline(always)]
> - fn try_write32(&self, value: u32, offset: usize) -> Result
> + fn try_write32(self, value: u32, offset: usize) -> Result
> where
> usize: IoLoc<Self::Target, u32, IoType = u32>,
> Self: IoCapable<u32>,
> @@ -407,7 +409,7 @@ fn try_write32(&self, value: u32, offset: usize) -> Result
>
> /// Fallible 64-bit write with runtime bounds check.
> #[inline(always)]
> - fn try_write64(&self, value: u64, offset: usize) -> Result
> + fn try_write64(self, value: u64, offset: usize) -> Result
> where
> usize: IoLoc<Self::Target, u64, IoType = u64>,
> Self: IoCapable<u64>,
> @@ -417,7 +419,7 @@ fn try_write64(&self, value: u64, offset: usize) -> Result
>
> /// Infallible 8-bit read with compile-time bounds check.
> #[inline(always)]
> - fn read8(&self, offset: usize) -> u8
> + fn read8(self, offset: usize) -> u8
> where
> usize: IoLoc<Self::Target, u8, IoType = u8>,
> Self: IoCapable<u8>,
> @@ -427,7 +429,7 @@ fn read8(&self, offset: usize) -> u8
>
> /// Infallible 16-bit read with compile-time bounds check.
> #[inline(always)]
> - fn read16(&self, offset: usize) -> u16
> + fn read16(self, offset: usize) -> u16
> where
> usize: IoLoc<Self::Target, u16, IoType = u16>,
> Self: IoCapable<u16>,
> @@ -437,7 +439,7 @@ fn read16(&self, offset: usize) -> u16
>
> /// Infallible 32-bit read with compile-time bounds check.
> #[inline(always)]
> - fn read32(&self, offset: usize) -> u32
> + fn read32(self, offset: usize) -> u32
> where
> usize: IoLoc<Self::Target, u32, IoType = u32>,
> Self: IoCapable<u32>,
> @@ -447,7 +449,7 @@ fn read32(&self, offset: usize) -> u32
>
> /// Infallible 64-bit read with compile-time bounds check.
> #[inline(always)]
> - fn read64(&self, offset: usize) -> u64
> + fn read64(self, offset: usize) -> u64
> where
> usize: IoLoc<Self::Target, u64, IoType = u64>,
> Self: IoCapable<u64>,
> @@ -457,7 +459,7 @@ fn read64(&self, offset: usize) -> u64
>
> /// Infallible 8-bit write with compile-time bounds check.
> #[inline(always)]
> - fn write8(&self, value: u8, offset: usize)
> + fn write8(self, value: u8, offset: usize)
> where
> usize: IoLoc<Self::Target, u8, IoType = u8>,
> Self: IoCapable<u8>,
> @@ -467,7 +469,7 @@ fn write8(&self, value: u8, offset: usize)
>
> /// Infallible 16-bit write with compile-time bounds check.
> #[inline(always)]
> - fn write16(&self, value: u16, offset: usize)
> + fn write16(self, value: u16, offset: usize)
> where
> usize: IoLoc<Self::Target, u16, IoType = u16>,
> Self: IoCapable<u16>,
> @@ -477,7 +479,7 @@ fn write16(&self, value: u16, offset: usize)
>
> /// Infallible 32-bit write with compile-time bounds check.
> #[inline(always)]
> - fn write32(&self, value: u32, offset: usize)
> + fn write32(self, value: u32, offset: usize)
> where
> usize: IoLoc<Self::Target, u32, IoType = u32>,
> Self: IoCapable<u32>,
> @@ -487,7 +489,7 @@ fn write32(&self, value: u32, offset: usize)
>
> /// Infallible 64-bit write with compile-time bounds check.
> #[inline(always)]
> - fn write64(&self, value: u64, offset: usize)
> + fn write64(self, value: u64, offset: usize)
> where
> usize: IoLoc<Self::Target, u64, IoType = u64>,
> Self: IoCapable<u64>,
> @@ -518,7 +520,7 @@ fn write64(&self, value: u64, offset: usize)
> /// }
> /// ```
> #[inline(always)]
> - fn try_read<T, L>(&self, location: L) -> Result<T>
> + fn try_read<T, L>(self, location: L) -> Result<T>
> where
> L: IoLoc<Self::Target, T>,
> Self: IoCapable<L::IoType>,
> @@ -552,7 +554,7 @@ fn try_read<T, L>(&self, location: L) -> Result<T>
> /// }
> /// ```
> #[inline(always)]
> - fn try_write<T, L>(&self, location: L, value: T) -> Result
> + fn try_write<T, L>(self, location: L, value: T) -> Result
> where
> L: IoLoc<Self::Target, T>,
> Self: IoCapable<L::IoType>,
> @@ -598,7 +600,7 @@ fn try_write<T, L>(&self, location: L, value: T) -> Result
> /// }
> /// ```
> #[inline(always)]
> - fn try_write_reg<T, L, V>(&self, value: V) -> Result
> + fn try_write_reg<T, L, V>(self, value: V) -> Result
> where
> L: IoLoc<Self::Target, T>,
> V: LocatedRegister<Self::Target, Location = L, Value = T>,
> @@ -631,7 +633,7 @@ fn try_write_reg<T, L, V>(&self, value: V) -> Result
> /// }
> /// ```
> #[inline(always)]
> - fn try_update<T, L, F>(&self, location: L, f: F) -> Result
> + fn try_update<T, L, F>(self, location: L, f: F) -> Result
> where
> L: IoLoc<Self::Target, T>,
> Self: IoCapable<L::IoType>,
> @@ -670,7 +672,7 @@ fn try_update<T, L, F>(&self, location: L, f: F) -> Result
> /// }
> /// ```
> #[inline(always)]
> - fn read<T, L>(&self, location: L) -> T
> + fn read<T, L>(self, location: L) -> T
> where
> L: IoLoc<Self::Target, T>,
> Self: IoCapable<L::IoType>,
> @@ -702,7 +704,7 @@ fn read<T, L>(&self, location: L) -> T
> /// }
> /// ```
> #[inline(always)]
> - fn write<T, L>(&self, location: L, value: T)
> + fn write<T, L>(self, location: L, value: T)
> where
> L: IoLoc<Self::Target, T>,
> Self: IoCapable<L::IoType>,
> @@ -745,7 +747,7 @@ fn write<T, L>(&self, location: L, value: T)
> /// }
> /// ```
> #[inline(always)]
> - fn write_reg<T, L, V>(&self, value: V)
> + fn write_reg<T, L, V>(self, value: V)
> where
> L: IoLoc<Self::Target, T>,
> V: LocatedRegister<Self::Target, Location = L, Value = T>,
> @@ -778,7 +780,7 @@ fn write_reg<T, L, V>(&self, value: V)
> /// }
> /// ```
> #[inline(always)]
> - fn update<T, L, F>(&self, location: L, f: F)
> + fn update<T, L, F>(self, location: L, f: F)
> where
> L: IoLoc<Self::Target, T>,
> Self: IoCapable<L::IoType>,
> @@ -799,13 +801,13 @@ fn update<T, L, F>(&self, location: L, f: F)
> macro_rules! impl_mmio_io_capable {
> ($mmio:ident, $(#[$attr:meta])* $ty:ty, $read_fn:ident, $write_fn:ident)
> => {
> $(#[$attr])*
> - impl<const SIZE: usize> IoCapable<$ty> for $mmio<SIZE> {
> - unsafe fn io_read(&self, address: usize) -> $ty {
> + impl<const SIZE: usize> IoCapable<$ty> for &$mmio<SIZE> {
> + unsafe fn io_read(self, address: usize) -> $ty {
> // SAFETY: By the trait invariant `address` is a valid
> address for MMIO operations.
> unsafe { bindings::$read_fn(address as *const c_void) }
> }
>
> - unsafe fn io_write(&self, value: $ty, address: usize) {
> + unsafe fn io_write(self, value: $ty, address: usize) {
> // SAFETY: By the trait invariant `address` is a valid
> address for MMIO operations.
> unsafe { bindings::$write_fn(value, address as *mut c_void) }
> }
> @@ -826,18 +828,18 @@ unsafe fn io_write(&self, value: $ty, address: usize) {
> writeq
> );
>
> -impl<const SIZE: usize> Io for Mmio<SIZE> {
> +impl<'a, const SIZE: usize> Io for &'a Mmio<SIZE> {
> type Target = Region<SIZE>;
>
> /// Returns the base address of this mapping.
> #[inline]
> - fn addr(&self) -> usize {
> + fn addr(self) -> usize {
> self.0.addr()
> }
>
> /// Returns the maximum size of this mapping.
> #[inline]
> - fn maxsize(&self) -> usize {
> + fn maxsize(self) -> usize {
> self.0.maxsize()
> }
> }
> @@ -864,16 +866,16 @@ pub unsafe fn from_raw(raw: &MmioRaw<SIZE>) -> &Self {
> #[repr(transparent)]
> pub struct RelaxedMmio<const SIZE: usize = 0>(Mmio<SIZE>);
>
> -impl<const SIZE: usize> Io for RelaxedMmio<SIZE> {
> +impl<'a, const SIZE: usize> Io for &'a RelaxedMmio<SIZE> {
> type Target = Region<SIZE>;
>
> #[inline]
> - fn addr(&self) -> usize {
> + fn addr(self) -> usize {
> self.0.addr()
> }
>
> #[inline]
> - fn maxsize(&self) -> usize {
> + fn maxsize(self) -> usize {
> self.0.maxsize()
> }
> }
> diff --git a/rust/kernel/pci/io.rs b/rust/kernel/pci/io.rs
> index b4996aa059d8..505305cd9b86 100644
> --- a/rust/kernel/pci/io.rs
> +++ b/rust/kernel/pci/io.rs
> @@ -79,8 +79,8 @@ pub struct ConfigSpace<'a, S: ?Sized + ConfigSpaceKind =
> Extended> {
> /// Implements [`IoCapable`] on [`ConfigSpace`] for `$ty` using `$read_fn`
> and `$write_fn`.
> macro_rules! impl_config_space_io_capable {
> ($ty:ty, $read_fn:ident, $write_fn:ident) => {
> - impl<'a, S: ?Sized + ConfigSpaceKind> IoCapable<$ty> for
> ConfigSpace<'a, S> {
> - unsafe fn io_read(&self, address: usize) -> $ty {
> + impl<'a, S: ?Sized + ConfigSpaceKind> IoCapable<$ty> for
> &ConfigSpace<'a, S> {
> + unsafe fn io_read(self, address: usize) -> $ty {
> let mut val: $ty = 0;
>
> // Return value from C function is ignored in infallible
> accessors.
> @@ -94,7 +94,7 @@ unsafe fn io_read(&self, address: usize) -> $ty {
> val
> }
>
> - unsafe fn io_write(&self, value: $ty, address: usize) {
> + unsafe fn io_write(self, value: $ty, address: usize) {
> // Return value from C function is ignored in infallible
> accessors.
> let _ret =
> // SAFETY: By the type invariant `self.pdev` is a valid
> address.
> @@ -112,18 +112,18 @@ unsafe fn io_write(&self, value: $ty, address: usize) {
> impl_config_space_io_capable!(u16, pci_read_config_word,
> pci_write_config_word);
> impl_config_space_io_capable!(u32, pci_read_config_dword,
> pci_write_config_dword);
>
> -impl<'a, S: ?Sized + ConfigSpaceKind> Io for ConfigSpace<'a, S> {
> +impl<'a, S: ?Sized + ConfigSpaceKind> Io for &ConfigSpace<'a, S> {
> type Target = S;
>
> /// Returns the base address of the I/O region. It is always 0 for
> configuration space.
> #[inline]
> - fn addr(&self) -> usize {
> + fn addr(self) -> usize {
> 0
> }
>
> /// Returns the maximum size of the configuration space.
> #[inline]
> - fn maxsize(&self) -> usize {
> + fn maxsize(self) -> usize {
> self.pdev.cfg_size().into_raw()
> }
> }
>
> --
> 2.54.0
>
>
Reviewed-by: Daniel Almeida <[email protected]>
