[PATCH v8 06/10] rust: io: use generic read/write accessors for primitive accesses
From: Alexandre Courbot
Date: Mon Mar 09 2026 - 11:22:26 EST
By providing the required `IoLoc` implementations on `usize`, we can
leverage the generic accessors and reduce the number of unsafe blocks in
the module.
This also allows us to directly call the generic `read/write/update`
methods with primitive types, so add examples illustrating this.
Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
---
rust/kernel/io.rs | 199 +++++++++++++++++++++++++++++++++++-------------------
1 file changed, 131 insertions(+), 68 deletions(-)
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 1db6572f4a42..ed6fab001a39 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -197,6 +197,25 @@ pub trait IoLoc<T> {
fn offset(&self) -> usize;
}
+/// Implements [`IoLoc<$ty>`] for [`usize`], allowing to use `usize` as a parameter of
+/// [`Io::read`] and [`Io::write`].
+macro_rules! impl_usize_ioloc {
+ ($($ty:ty),*) => {
+ $(
+ impl IoLoc<$ty> for usize {
+ type IoType = $ty;
+
+ fn offset(&self) -> usize {
+ *self
+ }
+ }
+ )*
+ }
+}
+
+// Provide the ability to read any primitive type from a [`usize`].
+impl_usize_ioloc!(u8, u16, u32, u64);
+
/// Types implementing this trait (e.g. MMIO BARs or PCI config regions)
/// can perform I/O operations on regions of memory.
///
@@ -241,10 +260,7 @@ fn try_read8(&self, offset: usize) -> Result<u8>
where
Self: IoCapable<u8>,
{
- let address = self.io_addr::<u8>(offset)?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- Ok(unsafe { self.io_read(address) })
+ self.try_read(offset)
}
/// Fallible 16-bit read with runtime bounds check.
@@ -253,10 +269,7 @@ fn try_read16(&self, offset: usize) -> Result<u16>
where
Self: IoCapable<u16>,
{
- let address = self.io_addr::<u16>(offset)?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- Ok(unsafe { self.io_read(address) })
+ self.try_read(offset)
}
/// Fallible 32-bit read with runtime bounds check.
@@ -265,10 +278,7 @@ fn try_read32(&self, offset: usize) -> Result<u32>
where
Self: IoCapable<u32>,
{
- let address = self.io_addr::<u32>(offset)?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- Ok(unsafe { self.io_read(address) })
+ self.try_read(offset)
}
/// Fallible 64-bit read with runtime bounds check.
@@ -277,10 +287,7 @@ fn try_read64(&self, offset: usize) -> Result<u64>
where
Self: IoCapable<u64>,
{
- let address = self.io_addr::<u64>(offset)?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- Ok(unsafe { self.io_read(address) })
+ self.try_read(offset)
}
/// Fallible 8-bit write with runtime bounds check.
@@ -289,11 +296,7 @@ fn try_write8(&self, value: u8, offset: usize) -> Result
where
Self: IoCapable<u8>,
{
- let address = self.io_addr::<u8>(offset)?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- unsafe { self.io_write(value, address) };
- Ok(())
+ self.try_write(offset, value)
}
/// Fallible 16-bit write with runtime bounds check.
@@ -302,11 +305,7 @@ fn try_write16(&self, value: u16, offset: usize) -> Result
where
Self: IoCapable<u16>,
{
- let address = self.io_addr::<u16>(offset)?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- unsafe { self.io_write(value, address) };
- Ok(())
+ self.try_write(offset, value)
}
/// Fallible 32-bit write with runtime bounds check.
@@ -315,11 +314,7 @@ fn try_write32(&self, value: u32, offset: usize) -> Result
where
Self: IoCapable<u32>,
{
- let address = self.io_addr::<u32>(offset)?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- unsafe { self.io_write(value, address) };
- Ok(())
+ self.try_write(offset, value)
}
/// Fallible 64-bit write with runtime bounds check.
@@ -328,11 +323,7 @@ fn try_write64(&self, value: u64, offset: usize) -> Result
where
Self: IoCapable<u64>,
{
- let address = self.io_addr::<u64>(offset)?;
-
- // SAFETY: `address` has been validated by `io_addr`.
- unsafe { self.io_write(value, address) };
- Ok(())
+ self.try_write(offset, value)
}
/// Infallible 8-bit read with compile-time bounds check.
@@ -341,10 +332,7 @@ fn read8(&self, offset: usize) -> u8
where
Self: IoKnownSize + IoCapable<u8>,
{
- let address = self.io_addr_assert::<u8>(offset);
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_read(address) }
+ self.read(offset)
}
/// Infallible 16-bit read with compile-time bounds check.
@@ -353,10 +341,7 @@ fn read16(&self, offset: usize) -> u16
where
Self: IoKnownSize + IoCapable<u16>,
{
- let address = self.io_addr_assert::<u16>(offset);
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_read(address) }
+ self.read(offset)
}
/// Infallible 32-bit read with compile-time bounds check.
@@ -365,10 +350,7 @@ fn read32(&self, offset: usize) -> u32
where
Self: IoKnownSize + IoCapable<u32>,
{
- let address = self.io_addr_assert::<u32>(offset);
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_read(address) }
+ self.read(offset)
}
/// Infallible 64-bit read with compile-time bounds check.
@@ -377,10 +359,7 @@ fn read64(&self, offset: usize) -> u64
where
Self: IoKnownSize + IoCapable<u64>,
{
- let address = self.io_addr_assert::<u64>(offset);
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_read(address) }
+ self.read(offset)
}
/// Infallible 8-bit write with compile-time bounds check.
@@ -389,10 +368,7 @@ fn write8(&self, value: u8, offset: usize)
where
Self: IoKnownSize + IoCapable<u8>,
{
- let address = self.io_addr_assert::<u8>(offset);
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_write(value, address) }
+ self.write(offset, value)
}
/// Infallible 16-bit write with compile-time bounds check.
@@ -401,10 +377,7 @@ fn write16(&self, value: u16, offset: usize)
where
Self: IoKnownSize + IoCapable<u16>,
{
- let address = self.io_addr_assert::<u16>(offset);
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_write(value, address) }
+ self.write(offset, value)
}
/// Infallible 32-bit write with compile-time bounds check.
@@ -413,10 +386,7 @@ fn write32(&self, value: u32, offset: usize)
where
Self: IoKnownSize + IoCapable<u32>,
{
- let address = self.io_addr_assert::<u32>(offset);
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_write(value, address) }
+ self.write(offset, value)
}
/// Infallible 64-bit write with compile-time bounds check.
@@ -425,13 +395,28 @@ fn write64(&self, value: u64, offset: usize)
where
Self: IoKnownSize + IoCapable<u64>,
{
- let address = self.io_addr_assert::<u64>(offset);
-
- // SAFETY: `address` has been validated by `io_addr_assert`.
- unsafe { self.io_write(value, address) }
+ self.write(offset, value)
}
/// Generic fallible read with runtime bounds check.
+ ///
+ /// # Examples
+ ///
+ /// Read a primitive type from an I/O address:
+ ///
+ /// ```no_run
+ /// use kernel::io::{Io, Mmio};
+ ///
+ /// fn do_reads(io: &Mmio) -> Result {
+ /// // 32-bit read from address `0x10`.
+ /// let v: u32 = io.try_read(0x10)?;
+ ///
+ /// // 8-bit read from address `0xfff`.
+ /// let v: u8 = io.try_read(0xfff)?;
+ ///
+ /// Ok(())
+ /// }
+ /// ```
#[inline(always)]
fn try_read<T, L>(&self, location: L) -> Result<T>
where
@@ -445,6 +430,24 @@ fn try_read<T, L>(&self, location: L) -> Result<T>
}
/// Generic fallible write with runtime bounds check.
+ ///
+ /// # Examples
+ ///
+ /// Write a primitive type to an I/O address:
+ ///
+ /// ```no_run
+ /// use kernel::io::{Io, Mmio};
+ ///
+ /// fn do_writes(io: &Mmio) -> Result {
+ /// // 32-bit write of value `1` at address `0x10`.
+ /// io.try_write(0x10, 1u32)?;
+ ///
+ /// // 8-bit write of value `0xff` at address `0xfff`.
+ /// io.try_write(0xfff, 0xffu8)?;
+ ///
+ /// Ok(())
+ /// }
+ /// ```
#[inline(always)]
fn try_write<T, L>(&self, location: L, value: T) -> Result
where
@@ -464,6 +467,20 @@ fn try_write<T, L>(&self, location: L, value: T) -> Result
///
/// Caution: this does not perform any synchronization. Race conditions can occur in case of
/// concurrent access.
+ ///
+ /// # Examples
+ ///
+ /// Read the u32 value at address `0x10`, increment it, and store the updated value back:
+ ///
+ /// ```no_run
+ /// use kernel::io::{Io, Mmio};
+ ///
+ /// fn do_update(io: &Mmio<0x1000>) -> Result {
+ /// io.try_update(0x10, |v: u32| {
+ /// v + 1
+ /// })
+ /// }
+ /// ```
#[inline(always)]
fn try_update<T, L, F>(&self, location: L, f: F) -> Result
where
@@ -484,6 +501,22 @@ fn try_update<T, L, F>(&self, location: L, f: F) -> Result
}
/// Generic infallible read with compile-time bounds check.
+ ///
+ /// # Examples
+ ///
+ /// Read a primitive type from an I/O address:
+ ///
+ /// ```no_run
+ /// use kernel::io::{Io, Mmio};
+ ///
+ /// fn do_reads(io: &Mmio<0x1000>) {
+ /// // 32-bit read from address `0x10`.
+ /// let v: u32 = io.read(0x10);
+ ///
+ /// // 8-bit read from the top of the I/O space.
+ /// let v: u8 = io.read(0xfff);
+ /// }
+ /// ```
#[inline(always)]
fn read<T, L>(&self, location: L) -> T
where
@@ -497,6 +530,22 @@ fn read<T, L>(&self, location: L) -> T
}
/// Generic infallible write with compile-time bounds check.
+ ///
+ /// # Examples
+ ///
+ /// Write a primitive type to an I/O address:
+ ///
+ /// ```no_run
+ /// use kernel::io::{Io, Mmio};
+ ///
+ /// fn do_writes(io: &Mmio<0x1000>) {
+ /// // 32-bit write of value `1` at address `0x10`.
+ /// io.write(0x10, 1u32);
+ ///
+ /// // 8-bit write of value `0xff` at the top of the I/O space.
+ /// io.write(0xfff, 0xffu8);
+ /// }
+ /// ```
#[inline(always)]
fn write<T, L>(&self, location: L, value: T)
where
@@ -514,6 +563,20 @@ fn write<T, L>(&self, location: L, value: T)
///
/// Caution: this does not perform any synchronization. Race conditions can occur in case of
/// concurrent access.
+ ///
+ /// # Examples
+ ///
+ /// Read the u32 value at address `0x10`, increment it, and store the updated value back:
+ ///
+ /// ```no_run
+ /// use kernel::io::{Io, Mmio};
+ ///
+ /// fn do_update(io: &Mmio<0x1000>) {
+ /// io.update(0x10, |v: u32| {
+ /// v + 1
+ /// })
+ /// }
+ /// ```
#[inline(always)]
fn update<T, L, F>(&self, location: L, f: F)
where
--
2.53.0