[PATCH v3 09/19] rust: io: use view types instead of addresses for `Io`
From: Gary Guo
Date: Mon Jun 08 2026 - 16:02:43 EST
Currently, `io_read` and `io_write` methods require the exact type of `Io`
plus an address. This means that they need to be monomorphized for each
different `Io` instance. This also means that multiple I/O implementors for
the same I/O kind needs to duplicate implementation (e.g. `Mmio` and
`MmioOwned`).
Create a new `IoBackend` trait and define these operations on it instead.
The operations are just going to receive a view type and operate on them.
This has the additional advantage that the invariants can be moved from the
trait (and guaranteed via `unsafe`) to type invariants on the canonical
view types of the backends, so `io_read` and `io_write` can be safe.
Note that view type is needed; addresses are insufficient in this
designk, as they do not carry sufficient information. For example,
`ConfigSpace` needs `&pci::Device` in addition to the address.
Signed-off-by: Gary Guo <gary@xxxxxxxxxxx>
---
rust/kernel/io.rs | 345 ++++++++++++++++++++++++++------------------------
rust/kernel/pci/io.rs | 70 ++++++----
2 files changed, 224 insertions(+), 191 deletions(-)
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 771372a8aa36..d09d9864858d 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -246,6 +246,38 @@ const fn offset_valid<U>(base: usize, offset: usize, size: usize) -> bool {
}
}
+/// I/O backends.
+///
+/// This is an abstract representation to be implemented by arbitrary I/O
+/// backends (e.g. MMIO, PCI config space, etc.).
+///
+/// The base trait only defines the projection operations; which I/O methods are available depends
+/// on which [`IoCapable<T>`] traits are implemented for the type. For example, 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.
+///
+/// This trait is separate from the `Io` trait as multiple different I/O types may share the same
+/// operation.
+pub trait IoBackend {
+ /// View type for this I/O backend.
+ type View<'a, T: ?Sized + KnownSize>: Io<'a, Backend = Self, Target = T>;
+
+ /// Convert a `view` to a raw pointer for projection.
+ fn as_ptr<'a, T: ?Sized + KnownSize>(view: Self::View<'a, T>) -> *mut T;
+
+ /// Project `view` to its subregion indicated by `ptr`.
+ ///
+ /// If input `view` is valid, returned view must also be valid.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must be a projection of `Self::as_ptr(view)`.
+ unsafe fn project_view<'a, T: ?Sized + KnownSize, U: ?Sized + KnownSize>(
+ view: Self::View<'a, T>,
+ ptr: *mut U,
+ ) -> Self::View<'a, U>;
+}
+
/// Trait indicating that an I/O backend supports operations of a certain type and providing an
/// implementation for these operations.
///
@@ -254,22 +286,12 @@ const fn offset_valid<U>(base: usize, offset: usize, size: usize) -> bool {
/// 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> {
- /// Performs an I/O read of type `T` at `address` and returns the result.
- ///
- /// # Safety
- ///
- /// - 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;
+pub trait IoCapable<T>: IoBackend {
+ /// Performs an I/O read of type `T` at `view` and returns the result.
+ fn io_read<'a>(view: Self::View<'a, T>) -> T;
- /// Performs an I/O write of `value` at `address`.
- ///
- /// # Safety
- ///
- /// - 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);
+ /// Performs an I/O write of `value` at `view`.
+ fn io_write<'a>(view: Self::View<'a, T>, value: T);
}
/// Describes a given I/O location: its offset, width, and type to convert the raw value from and
@@ -321,56 +343,54 @@ fn offset(self) -> usize {
/// 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
+/// - Method to convert into [`IoBackend::View`].
/// - 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: Copy {
+/// Which I/O methods are available depends on the associated [`IoBackend`] implementation.
+pub trait Io<'a>: Copy {
+ /// Type that defines all I/O operations.
+ type Backend: IoBackend;
+
/// 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;
-
- /// Returns the maximum size of this mapping.
- fn maxsize(self) -> usize;
+ /// Return a view that covers the full region.
+ fn as_view(self) -> <Self::Backend as IoBackend>::View<'a, Self::Target>;
- /// Returns the absolute I/O address for a given `offset`,
- /// performing compile-time bound checks.
+ /// Returns a view 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 {
- // We cannot check alignment with `offset_valid` using `self.addr()`. So set 0 for it and
+ fn io_addr_assert<U>(self, offset: usize) -> <Self::Backend as IoBackend>::View<'a, U> {
+ // We cannot check alignment with `offset_valid` using `ptr.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`.
const_assert!(Alignment::of::<U>().as_usize() <= Self::Target::MIN_ALIGN.as_usize());
build_assert!(offset_valid::<U>(0, offset, Self::Target::MIN_SIZE));
- self.addr() + offset
+ let view = self.as_view();
+ let ptr = Self::Backend::as_ptr(view);
+ let projected_ptr = ptr.cast::<U>().wrapping_byte_add(offset);
+ // SAFETY: `offset_valid` checks for size and alignment and therefore `projected_ptr` is a
+ // valid projection.
+ unsafe { Self::Backend::project_view(view, projected_ptr) }
}
- /// Returns the absolute I/O address for a given `offset`,
- /// performing runtime bound checks.
+ /// Returns a view for a given `offset`, performing runtime bound checks.
#[inline]
- fn io_addr<U>(self, offset: usize) -> Result<usize> {
- if !offset_valid::<U>(self.addr(), offset, self.maxsize()) {
+ fn io_addr<U>(self, offset: usize) -> Result<<Self::Backend as IoBackend>::View<'a, U>> {
+ let view = self.as_view();
+ let ptr = Self::Backend::as_ptr(view);
+
+ if !offset_valid::<U>(ptr.addr(), offset, KnownSize::size(ptr)) {
return Err(EINVAL);
}
- // Probably no need to check, since the safety requirements of `Self::new` guarantee that
- // this can't overflow.
- self.addr().checked_add(offset).ok_or(EINVAL)
+ let projected_ptr = ptr.cast::<U>().wrapping_byte_add(offset);
+ // SAFETY: `offset_valid` checks for size and alignment and therefore `projected_ptr` is a
+ // valid projection.
+ Ok(unsafe { Self::Backend::project_view(view, projected_ptr) })
}
/// Fallible 8-bit read with runtime bounds check.
@@ -378,7 +398,7 @@ fn io_addr<U>(self, offset: usize) -> Result<usize> {
fn try_read8(self, offset: usize) -> Result<u8>
where
usize: IoLoc<Self::Target, u8, IoType = u8>,
- Self: IoCapable<u8>,
+ Self::Backend: IoCapable<u8>,
{
self.try_read(offset)
}
@@ -388,7 +408,7 @@ fn try_read8(self, offset: usize) -> Result<u8>
fn try_read16(self, offset: usize) -> Result<u16>
where
usize: IoLoc<Self::Target, u16, IoType = u16>,
- Self: IoCapable<u16>,
+ Self::Backend: IoCapable<u16>,
{
self.try_read(offset)
}
@@ -398,7 +418,7 @@ fn try_read16(self, offset: usize) -> Result<u16>
fn try_read32(self, offset: usize) -> Result<u32>
where
usize: IoLoc<Self::Target, u32, IoType = u32>,
- Self: IoCapable<u32>,
+ Self::Backend: IoCapable<u32>,
{
self.try_read(offset)
}
@@ -408,7 +428,7 @@ fn try_read32(self, offset: usize) -> Result<u32>
fn try_read64(self, offset: usize) -> Result<u64>
where
usize: IoLoc<Self::Target, u64, IoType = u64>,
- Self: IoCapable<u64>,
+ Self::Backend: IoCapable<u64>,
{
self.try_read(offset)
}
@@ -418,7 +438,7 @@ fn try_read64(self, offset: usize) -> Result<u64>
fn try_write8(self, value: u8, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u8, IoType = u8>,
- Self: IoCapable<u8>,
+ Self::Backend: IoCapable<u8>,
{
self.try_write(offset, value)
}
@@ -428,7 +448,7 @@ fn try_write8(self, value: u8, offset: usize) -> Result
fn try_write16(self, value: u16, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u16, IoType = u16>,
- Self: IoCapable<u16>,
+ Self::Backend: IoCapable<u16>,
{
self.try_write(offset, value)
}
@@ -438,7 +458,7 @@ fn try_write16(self, value: u16, offset: usize) -> Result
fn try_write32(self, value: u32, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u32, IoType = u32>,
- Self: IoCapable<u32>,
+ Self::Backend: IoCapable<u32>,
{
self.try_write(offset, value)
}
@@ -448,7 +468,7 @@ fn try_write32(self, value: u32, offset: usize) -> Result
fn try_write64(self, value: u64, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u64, IoType = u64>,
- Self: IoCapable<u64>,
+ Self::Backend: IoCapable<u64>,
{
self.try_write(offset, value)
}
@@ -458,7 +478,7 @@ fn try_write64(self, value: u64, offset: usize) -> Result
fn read8(self, offset: usize) -> u8
where
usize: IoLoc<Self::Target, u8, IoType = u8>,
- Self: IoCapable<u8>,
+ Self::Backend: IoCapable<u8>,
{
self.read(offset)
}
@@ -468,7 +488,7 @@ fn read8(self, offset: usize) -> u8
fn read16(self, offset: usize) -> u16
where
usize: IoLoc<Self::Target, u16, IoType = u16>,
- Self: IoCapable<u16>,
+ Self::Backend: IoCapable<u16>,
{
self.read(offset)
}
@@ -478,7 +498,7 @@ fn read16(self, offset: usize) -> u16
fn read32(self, offset: usize) -> u32
where
usize: IoLoc<Self::Target, u32, IoType = u32>,
- Self: IoCapable<u32>,
+ Self::Backend: IoCapable<u32>,
{
self.read(offset)
}
@@ -488,7 +508,7 @@ fn read32(self, offset: usize) -> u32
fn read64(self, offset: usize) -> u64
where
usize: IoLoc<Self::Target, u64, IoType = u64>,
- Self: IoCapable<u64>,
+ Self::Backend: IoCapable<u64>,
{
self.read(offset)
}
@@ -498,7 +518,7 @@ fn read64(self, offset: usize) -> u64
fn write8(self, value: u8, offset: usize)
where
usize: IoLoc<Self::Target, u8, IoType = u8>,
- Self: IoCapable<u8>,
+ Self::Backend: IoCapable<u8>,
{
self.write(offset, value)
}
@@ -508,7 +528,7 @@ fn write8(self, value: u8, offset: usize)
fn write16(self, value: u16, offset: usize)
where
usize: IoLoc<Self::Target, u16, IoType = u16>,
- Self: IoCapable<u16>,
+ Self::Backend: IoCapable<u16>,
{
self.write(offset, value)
}
@@ -518,7 +538,7 @@ fn write16(self, value: u16, offset: usize)
fn write32(self, value: u32, offset: usize)
where
usize: IoLoc<Self::Target, u32, IoType = u32>,
- Self: IoCapable<u32>,
+ Self::Backend: IoCapable<u32>,
{
self.write(offset, value)
}
@@ -528,7 +548,7 @@ fn write32(self, value: u32, offset: usize)
fn write64(self, value: u64, offset: usize)
where
usize: IoLoc<Self::Target, u64, IoType = u64>,
- Self: IoCapable<u64>,
+ Self::Backend: IoCapable<u64>,
{
self.write(offset, value)
}
@@ -560,12 +580,10 @@ fn write64(self, value: u64, offset: usize)
fn try_read<T, L>(self, location: L) -> Result<T>
where
L: IoLoc<Self::Target, T>,
- Self: IoCapable<L::IoType>,
+ Self::Backend: IoCapable<L::IoType>,
{
- let address = self.io_addr::<L::IoType>(location.offset())?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- Ok(unsafe { self.io_read(address) }.into())
+ let view = self.io_addr::<L::IoType>(location.offset())?;
+ Ok(Self::Backend::io_read(view).into())
}
/// Generic fallible write with runtime bounds check.
@@ -595,14 +613,11 @@ fn try_read<T, L>(self, location: L) -> Result<T>
fn try_write<T, L>(self, location: L, value: T) -> Result
where
L: IoLoc<Self::Target, T>,
- Self: IoCapable<L::IoType>,
+ Self::Backend: IoCapable<L::IoType>,
{
- let address = self.io_addr::<L::IoType>(location.offset())?;
+ let view = self.io_addr::<L::IoType>(location.offset())?;
let io_value = value.into();
-
- // SAFETY: `address` has been validated by `io_addr`.
- unsafe { self.io_write(io_value, address) }
-
+ Self::Backend::io_write(view, io_value);
Ok(())
}
@@ -643,7 +658,7 @@ 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>,
- Self: IoCapable<L::IoType>,
+ Self::Backend: IoCapable<L::IoType>,
{
let (location, value) = value.into_io_op();
@@ -676,17 +691,14 @@ fn try_write_reg<T, L, V>(self, value: V) -> Result
fn try_update<T, L, F>(self, location: L, f: F) -> Result
where
L: IoLoc<Self::Target, T>,
- Self: IoCapable<L::IoType>,
+ Self::Backend: IoCapable<L::IoType>,
F: FnOnce(T) -> T,
{
- let address = self.io_addr::<L::IoType>(location.offset())?;
+ let view = self.io_addr::<L::IoType>(location.offset())?;
- // SAFETY: `address` has been validated by `io_addr`.
- let value: T = unsafe { self.io_read(address) }.into();
+ let value: T = Self::Backend::io_read(view).into();
let io_value = f(value).into();
-
- // SAFETY: `address` has been validated by `io_addr`.
- unsafe { self.io_write(io_value, address) }
+ Self::Backend::io_write(view, io_value);
Ok(())
}
@@ -716,12 +728,10 @@ fn try_update<T, L, F>(self, location: L, f: F) -> Result
fn read<T, L>(self, location: L) -> T
where
L: IoLoc<Self::Target, T>,
- Self: IoCapable<L::IoType>,
+ Self::Backend: IoCapable<L::IoType>,
{
- let address = self.io_addr_assert::<L::IoType>(location.offset());
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_read(address) }.into()
+ let view = self.io_addr_assert::<L::IoType>(location.offset());
+ Self::Backend::io_read(view).into()
}
/// Generic infallible write with compile-time bounds check.
@@ -749,13 +759,11 @@ fn read<T, L>(self, location: L) -> T
fn write<T, L>(self, location: L, value: T)
where
L: IoLoc<Self::Target, T>,
- Self: IoCapable<L::IoType>,
+ Self::Backend: IoCapable<L::IoType>,
{
- let address = self.io_addr_assert::<L::IoType>(location.offset());
+ let view = self.io_addr_assert::<L::IoType>(location.offset());
let io_value = value.into();
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_write(io_value, address) }
+ Self::Backend::io_write(view, io_value);
}
/// Generic infallible write of a fully-located register value.
@@ -794,7 +802,7 @@ fn write_reg<T, L, V>(self, value: V)
where
L: IoLoc<Self::Target, T>,
V: LocatedRegister<Self::Target, Location = L, Value = T>,
- Self: IoCapable<L::IoType>,
+ Self::Backend: IoCapable<L::IoType>,
{
let (location, value) = value.into_io_op();
@@ -827,17 +835,13 @@ fn write_reg<T, L, V>(self, value: V)
fn update<T, L, F>(self, location: L, f: F)
where
L: IoLoc<Self::Target, T>,
- Self: IoCapable<L::IoType>,
+ Self::Backend: IoCapable<L::IoType>,
F: FnOnce(T) -> T,
{
- let address = self.io_addr_assert::<L::IoType>(location.offset());
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- let value: T = unsafe { self.io_read(address) }.into();
+ let view = self.io_addr_assert::<L::IoType>(location.offset());
+ let value: T = Self::Backend::io_read(view).into();
let io_value = f(value).into();
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_write(io_value, address) }
+ Self::Backend::io_write(view, io_value);
}
}
@@ -881,78 +885,76 @@ unsafe impl<T: ?Sized + Sync> Send for Mmio<'_, T> {}
// SAFETY: `Mmio<'_, T>` is conceptually `&T` but in I/O memory.
unsafe impl<T: ?Sized + Sync> Sync for Mmio<'_, T> {}
-impl<T: ?Sized + KnownSize> Io for Mmio<'_, T> {
+impl<'a, T: ?Sized + KnownSize> Io<'a> for Mmio<'a, T> {
+ type Backend = MmioBackend;
type Target = T;
#[inline]
- fn addr(self) -> usize {
- self.ptr.addr()
+ fn as_view(self) -> Mmio<'a, T> {
+ self
}
+}
+
+/// I/O Backend for memory-mapped I/O.
+pub struct MmioBackend;
+
+impl IoBackend for MmioBackend {
+ type View<'a, T: ?Sized + KnownSize> = Mmio<'a, T>;
#[inline]
- fn maxsize(self) -> usize {
- KnownSize::size(self.ptr)
+ fn as_ptr<'a, T: ?Sized + KnownSize>(view: Self::View<'a, T>) -> *mut T {
+ view.ptr
+ }
+
+ #[inline]
+ unsafe fn project_view<'a, T: ?Sized + KnownSize, U: ?Sized + KnownSize>(
+ _view: Self::View<'a, T>,
+ ptr: *mut U,
+ ) -> Self::View<'a, U> {
+ // INVARIANT: Per safety requirement, `ptr` is projection from `view`, so it is also a valid
+ // memory-mapped I/O region.
+ Mmio {
+ ptr,
+ phantom: PhantomData,
+ }
}
}
-/// Implements [`IoCapable`] on `$mmio` for `$ty` using `$read_fn` and `$write_fn`.
+/// Implements [`IoCapable`] on `$backend` for `$ty` using `$read_fn` and `$write_fn`.
macro_rules! impl_mmio_io_capable {
- ($mmio:ident, $(#[$attr:meta])* $ty:ty, $read_fn:ident, $write_fn:ident) => {
- $(#[$attr])*
- impl<T: ?Sized> IoCapable<$ty> for $mmio<'_, T> {
+ ($backend: ident, $ty:ty, $read_fn:ident, $write_fn:ident) => {
+ impl IoCapable<$ty> for $backend {
#[inline]
- 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) }
+ fn io_read(view: <$backend as IoBackend>::View<'_, $ty>) -> $ty {
+ // SAFETY: By the type invariant, `view.ptr` is a valid address for MMIO operations.
+ unsafe { bindings::$read_fn(view.ptr.cast_const().cast()) }
}
#[inline]
- 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) }
+ fn io_write(view: <$backend as IoBackend>::View<'_, $ty>, value: $ty) {
+ // SAFETY: By the type invariant, `view.ptr` is a valid address for MMIO operations.
+ unsafe { bindings::$write_fn(value, view.ptr.cast()) }
}
}
};
}
// MMIO regions support 8, 16, and 32-bit accesses.
-impl_mmio_io_capable!(Mmio, u8, readb, writeb);
-impl_mmio_io_capable!(Mmio, u16, readw, writew);
-impl_mmio_io_capable!(Mmio, u32, readl, writel);
+impl_mmio_io_capable!(MmioBackend, u8, readb, writeb);
+impl_mmio_io_capable!(MmioBackend, u16, readw, writew);
+impl_mmio_io_capable!(MmioBackend, u32, readl, writel);
// MMIO regions on 64-bit systems also support 64-bit accesses.
#[cfg(CONFIG_64BIT)]
-impl_mmio_io_capable!(Mmio, u64, readq, writeq);
+impl_mmio_io_capable!(MmioBackend, u64, readq, writeq);
-impl<'a, const SIZE: usize> Io for &'a MmioOwned<SIZE> {
+impl<'a, const SIZE: usize> Io<'a> for &'a MmioOwned<SIZE> {
+ type Backend = MmioBackend;
type Target = Region<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.size()
- }
-}
-
-impl<'a, const SIZE: usize, T> IoCapable<T> for &'a MmioOwned<SIZE>
-where
- Mmio<'a, Region<SIZE>>: IoCapable<T>,
-{
- #[inline]
- unsafe fn io_read(self, address: usize) -> T {
- // SAFETY: Per safety requirement.
- unsafe { self.as_view().io_read(address) }
- }
-
- #[inline]
- unsafe fn io_write(self, value: T, address: usize) {
- // SAFETY: Per safety requirement.
- unsafe { self.as_view().io_write(value, address) }
+ fn as_view(self) -> Mmio<'a, Self::Target> {
+ // SAFETY: `Mmio` has same invariant as `MmioOwned`
+ unsafe { Mmio::from_raw(self.0) }
}
}
@@ -968,13 +970,6 @@ 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() }
}
-
- /// Return a view that covers the full region.
- #[inline]
- pub fn as_view(&self) -> Mmio<'_, Region<SIZE>> {
- // SAFETY: `Mmio` has same invariant as `MmioOwned`.
- unsafe { Mmio::from_raw(self.0) }
- }
}
/// [`Mmio`] but using relaxed accessors.
@@ -1000,17 +995,38 @@ fn clone(&self) -> Self {
}
}
-impl<T: ?Sized + KnownSize> Io for RelaxedMmio<'_, T> {
- type Target = T;
+/// I/O Backend for memory-mapped I/O, with relaxed access semantics.
+pub struct RelaxedMmioBackend;
+
+impl IoBackend for RelaxedMmioBackend {
+ type View<'a, T: ?Sized + KnownSize> = RelaxedMmio<'a, T>;
#[inline]
- fn addr(self) -> usize {
- self.ptr.addr()
+ fn as_ptr<'a, T: ?Sized + KnownSize>(view: Self::View<'a, T>) -> *mut T {
+ view.ptr
}
#[inline]
- fn maxsize(self) -> usize {
- KnownSize::size(self.ptr)
+ unsafe fn project_view<'a, T: ?Sized + KnownSize, U: ?Sized + KnownSize>(
+ _view: Self::View<'a, T>,
+ ptr: *mut U,
+ ) -> Self::View<'a, U> {
+ // INVARIANT: Per safety requirement, `ptr` is projection from `view`, so it is also a valid
+ // memory-mapped I/O region.
+ RelaxedMmio {
+ ptr,
+ phantom: PhantomData,
+ }
+ }
+}
+
+impl<'a, T: ?Sized + KnownSize> Io<'a> for RelaxedMmio<'a, T> {
+ type Backend = RelaxedMmioBackend;
+ type Target = T;
+
+ #[inline]
+ fn as_view(self) -> RelaxedMmio<'a, T> {
+ self
}
}
@@ -1046,14 +1062,9 @@ pub fn relaxed(self) -> RelaxedMmio<'a, T> {
}
// MMIO regions support 8, 16, and 32-bit accesses.
-impl_mmio_io_capable!(RelaxedMmio, u8, readb_relaxed, writeb_relaxed);
-impl_mmio_io_capable!(RelaxedMmio, u16, readw_relaxed, writew_relaxed);
-impl_mmio_io_capable!(RelaxedMmio, u32, readl_relaxed, writel_relaxed);
+impl_mmio_io_capable!(RelaxedMmioBackend, u8, readb_relaxed, writeb_relaxed);
+impl_mmio_io_capable!(RelaxedMmioBackend, u16, readw_relaxed, writew_relaxed);
+impl_mmio_io_capable!(RelaxedMmioBackend, u32, readl_relaxed, writel_relaxed);
// MMIO regions on 64-bit systems also support 64-bit accesses.
-impl_mmio_io_capable!(
- RelaxedMmio,
- #[cfg(CONFIG_64BIT)]
- u64,
- readq_relaxed,
- writeq_relaxed
-);
+#[cfg(CONFIG_64BIT)]
+impl_mmio_io_capable!(RelaxedMmioBackend, u64, readq_relaxed, writeq_relaxed);
diff --git a/rust/kernel/pci/io.rs b/rust/kernel/pci/io.rs
index a4cfa1ec6e62..9286b2e419f9 100644
--- a/rust/kernel/pci/io.rs
+++ b/rust/kernel/pci/io.rs
@@ -9,6 +9,7 @@
devres::Devres,
io::{
Io,
+ IoBackend,
IoCapable,
MmioOwned,
MmioRaw,
@@ -78,32 +79,57 @@ fn clone(&self) -> Self {
}
}
+/// I/O Backend for PCI configuration space.
+pub struct ConfigSpaceBackend;
+
+impl IoBackend for ConfigSpaceBackend {
+ type View<'a, T: ?Sized + KnownSize> = ConfigSpace<'a, T>;
+
+ #[inline]
+ fn as_ptr<'a, T: ?Sized + KnownSize>(view: ConfigSpace<'a, T>) -> *mut T {
+ view.ptr
+ }
+
+ #[inline]
+ unsafe fn project_view<'a, T: ?Sized + KnownSize, U: ?Sized + KnownSize>(
+ view: Self::View<'a, T>,
+ ptr: *mut U,
+ ) -> Self::View<'a, U> {
+ // INVARIANT: Per safety requirement.
+ ConfigSpace {
+ pdev: view.pdev,
+ ptr,
+ }
+ }
+}
+
/// Implements [`IoCapable`] on [`ConfigSpace`] for `$ty` using `$read_fn` and `$write_fn`.
macro_rules! impl_config_space_io_capable {
($ty:ty, $read_fn:ident, $write_fn:ident) => {
- impl<'a, T: ?Sized> IoCapable<$ty> for ConfigSpace<'a, T> {
- unsafe fn io_read(self, address: usize) -> $ty {
+ impl IoCapable<$ty> for ConfigSpaceBackend {
+ fn io_read(view: ConfigSpace<'_, $ty>) -> $ty {
+ // CAST: The offset is cast to `i32` because the C functions expect a 32-bit
+ // signed offset parameter. PCI configuration space size is at most 4096 bytes,
+ // so the value always fits within `i32` without truncation or sign change.
+ let addr = view.ptr.addr() as i32;
+
let mut val: $ty = 0;
// Return value from C function is ignored in infallible accessors.
- let _ret =
- // SAFETY: By the type invariant `self.pdev` is a valid address.
- // CAST: The offset is cast to `i32` because the C functions expect a 32-bit
- // signed offset parameter. PCI configuration space size is at most 4096 bytes,
- // so the value always fits within `i32` without truncation or sign change.
- unsafe { bindings::$read_fn(self.pdev.as_raw(), address as i32, &mut val) };
-
+ // SAFETY: By the type invariant `pdev` is a valid address.
+ let _ = unsafe { bindings::$read_fn(view.pdev.as_raw(), addr, &mut val) };
val
}
- unsafe fn io_write(self, value: $ty, address: usize) {
+ fn io_write(view: ConfigSpace<'_, $ty>, value: $ty) {
+ // CAST: The offset is cast to `i32` because the C functions expect a 32-bit
+ // signed offset parameter. PCI configuration space size is at most 4096 bytes,
+ // so the value always fits within `i32` without truncation or sign change.
+ let addr = view.ptr.addr() as i32;
+
// Return value from C function is ignored in infallible accessors.
- let _ret =
- // SAFETY: By the type invariant `self.pdev` is a valid address.
- // CAST: The offset is cast to `i32` because the C functions expect a 32-bit
- // signed offset parameter. PCI configuration space size is at most 4096 bytes,
- // so the value always fits within `i32` without truncation or sign change.
- unsafe { bindings::$write_fn(self.pdev.as_raw(), address as i32, value) };
+ // SAFETY: By the type invariant `pdev` is a valid address.
+ let _ = unsafe { bindings::$write_fn(view.pdev.as_raw(), addr, value) };
}
}
};
@@ -114,17 +140,13 @@ 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, T: ?Sized + KnownSize> Io for ConfigSpace<'a, T> {
+impl<'a, T: ?Sized + KnownSize> Io<'a> for ConfigSpace<'a, T> {
+ type Backend = ConfigSpaceBackend;
type Target = T;
#[inline]
- fn addr(self) -> usize {
- self.ptr.addr()
- }
-
- #[inline]
- fn maxsize(self) -> usize {
- KnownSize::size(self.ptr)
+ fn as_view(self) -> ConfigSpace<'a, T> {
+ self
}
}
--
2.54.0