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rust: io: restrict untyped IO access and register! to Region

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Currently the `Io` trait exposes a bunch of untyped IO accesses, but if the
`Io` region itself is typed, then it might be weird to have

    let io: Mmio<u32> = /* ... */;
    io.read8(1);

while not unsound, it is surely strange. Thus, restrict the untyped methods
and also the register macro to `Region` type only.

Implement it by adding a generic type to `IoLoc` indicating allowed base
types. This also paves the way to add typed register blocks in the future;
for example, we could use this mechanism to block driver A's `register!()`
generated macro from being used on driver B's MMIO. The same mechanism
could be used for relative IO registers. These are future opportunities,
and for now restrict everything to require `IoLoc<Region<SIZE>, _>`.

Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/rust-for-linux/DHLB3RO3OSF5.2R7F27U99BKLN@nvidia.com/
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20260706-io_projection-v6-3-72cd5d055d54@garyguo.net
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Gary Guo
2026-07-06 13:44:16 +01:00
committed by Danilo Krummrich
parent 65f6abf9fa
commit 6461c5776b
2 changed files with 44 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

49
rust/kernel/io.rs
View File

@@ -244,15 +244,16 @@ pub trait IoCapable<T> {
/// (for primitive types like [`u32`]) and typed ones (like those generated by the [`register!`]
/// macro).
///
/// An `IoLoc<T>` carries three pieces of information:
/// An `IoLoc<Base, T>` carries the following pieces of information:
///
/// - The valid `Base` to operate on. For most registers, this should be [`Region`].
/// - The offset to access (returned by [`IoLoc::offset`]),
/// - The width of the access (determined by [`IoLoc::IoType`]),
/// - The type `T` in which the raw data is returned or provided.
///
/// `T` and `IoLoc::IoType` may differ: for instance, a typed register has `T` = the register type
/// with its bitfields, and `IoType` = its backing primitive (e.g. `u32`).
pub trait IoLoc<T> {
pub trait IoLoc<Base: ?Sized, T> {
/// Size ([`u8`], [`u16`], etc) of the I/O performed on the returned [`offset`](IoLoc::offset).
type IoType: Into<T> + From<T>;
@@ -260,12 +261,12 @@ pub trait IoLoc<T> {
fn offset(self) -> usize;
}
/// Implements [`IoLoc<$ty>`] for [`usize`], allowing [`usize`] to be used as a parameter of
/// [`Io::read`] and [`Io::write`].
/// Implements [`IoLoc<Region<SIZE>, $ty>`] for [`usize`], allowing [`usize`] to be used as a
/// parameter of [`Io::read`] and [`Io::write`].
macro_rules! impl_usize_ioloc {
($($ty:ty),*) => {
$(
impl IoLoc<$ty> for usize {
impl<const SIZE: usize> IoLoc<Region<SIZE>, $ty> for usize {
type IoType = $ty;
#[inline(always)]
@@ -339,6 +340,7 @@ fn io_addr<U>(&self, offset: usize) -> Result<usize> {
#[inline(always)]
fn try_read8(&self, offset: usize) -> Result<u8>
where
usize: IoLoc<Self::Target, u8, IoType = u8>,
Self: IoCapable<u8>,
{
self.try_read(offset)
@@ -348,6 +350,7 @@ fn try_read8(&self, offset: usize) -> Result<u8>
#[inline(always)]
fn try_read16(&self, offset: usize) -> Result<u16>
where
usize: IoLoc<Self::Target, u16, IoType = u16>,
Self: IoCapable<u16>,
{
self.try_read(offset)
@@ -357,6 +360,7 @@ fn try_read16(&self, offset: usize) -> Result<u16>
#[inline(always)]
fn try_read32(&self, offset: usize) -> Result<u32>
where
usize: IoLoc<Self::Target, u32, IoType = u32>,
Self: IoCapable<u32>,
{
self.try_read(offset)
@@ -366,6 +370,7 @@ fn try_read32(&self, offset: usize) -> Result<u32>
#[inline(always)]
fn try_read64(&self, offset: usize) -> Result<u64>
where
usize: IoLoc<Self::Target, u64, IoType = u64>,
Self: IoCapable<u64>,
{
self.try_read(offset)
@@ -375,6 +380,7 @@ fn try_read64(&self, offset: usize) -> Result<u64>
#[inline(always)]
fn try_write8(&self, value: u8, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u8, IoType = u8>,
Self: IoCapable<u8>,
{
self.try_write(offset, value)
@@ -384,6 +390,7 @@ fn try_write8(&self, value: u8, offset: usize) -> Result
#[inline(always)]
fn try_write16(&self, value: u16, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u16, IoType = u16>,
Self: IoCapable<u16>,
{
self.try_write(offset, value)
@@ -393,6 +400,7 @@ fn try_write16(&self, value: u16, offset: usize) -> Result
#[inline(always)]
fn try_write32(&self, value: u32, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u32, IoType = u32>,
Self: IoCapable<u32>,
{
self.try_write(offset, value)
@@ -402,6 +410,7 @@ fn try_write32(&self, value: u32, offset: usize) -> Result
#[inline(always)]
fn try_write64(&self, value: u64, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u64, IoType = u64>,
Self: IoCapable<u64>,
{
self.try_write(offset, value)
@@ -411,6 +420,7 @@ fn try_write64(&self, value: u64, offset: usize) -> Result
#[inline(always)]
fn read8(&self, offset: usize) -> u8
where
usize: IoLoc<Self::Target, u8, IoType = u8>,
Self: IoCapable<u8>,
{
self.read(offset)
@@ -420,6 +430,7 @@ fn read8(&self, offset: usize) -> u8
#[inline(always)]
fn read16(&self, offset: usize) -> u16
where
usize: IoLoc<Self::Target, u16, IoType = u16>,
Self: IoCapable<u16>,
{
self.read(offset)
@@ -429,6 +440,7 @@ fn read16(&self, offset: usize) -> u16
#[inline(always)]
fn read32(&self, offset: usize) -> u32
where
usize: IoLoc<Self::Target, u32, IoType = u32>,
Self: IoCapable<u32>,
{
self.read(offset)
@@ -438,6 +450,7 @@ fn read32(&self, offset: usize) -> u32
#[inline(always)]
fn read64(&self, offset: usize) -> u64
where
usize: IoLoc<Self::Target, u64, IoType = u64>,
Self: IoCapable<u64>,
{
self.read(offset)
@@ -447,6 +460,7 @@ fn read64(&self, offset: usize) -> u64
#[inline(always)]
fn write8(&self, value: u8, offset: usize)
where
usize: IoLoc<Self::Target, u8, IoType = u8>,
Self: IoCapable<u8>,
{
self.write(offset, value)
@@ -456,6 +470,7 @@ fn write8(&self, value: u8, offset: usize)
#[inline(always)]
fn write16(&self, value: u16, offset: usize)
where
usize: IoLoc<Self::Target, u16, IoType = u16>,
Self: IoCapable<u16>,
{
self.write(offset, value)
@@ -465,6 +480,7 @@ fn write16(&self, value: u16, offset: usize)
#[inline(always)]
fn write32(&self, value: u32, offset: usize)
where
usize: IoLoc<Self::Target, u32, IoType = u32>,
Self: IoCapable<u32>,
{
self.write(offset, value)
@@ -474,6 +490,7 @@ fn write32(&self, value: u32, offset: usize)
#[inline(always)]
fn write64(&self, value: u64, offset: usize)
where
usize: IoLoc<Self::Target, u64, IoType = u64>,
Self: IoCapable<u64>,
{
self.write(offset, value)
@@ -504,7 +521,7 @@ fn write64(&self, value: u64, offset: usize)
#[inline(always)]
fn try_read<T, L>(&self, location: L) -> Result<T>
where
L: IoLoc<T>,
L: IoLoc<Self::Target, T>,
Self: IoCapable<L::IoType>,
{
let address = self.io_addr::<L::IoType>(location.offset())?;
@@ -538,7 +555,7 @@ fn try_read<T, L>(&self, location: L) -> Result<T>
#[inline(always)]
fn try_write<T, L>(&self, location: L, value: T) -> Result
where
L: IoLoc<T>,
L: IoLoc<Self::Target, T>,
Self: IoCapable<L::IoType>,
{
let address = self.io_addr::<L::IoType>(location.offset())?;
@@ -584,8 +601,8 @@ fn try_write<T, L>(&self, location: L, value: T) -> Result
#[inline(always)]
fn try_write_reg<T, L, V>(&self, value: V) -> Result
where
L: IoLoc<T>,
V: LocatedRegister<Location = L, Value = T>,
L: IoLoc<Self::Target, T>,
V: LocatedRegister<Self::Target, Location = L, Value = T>,
Self: IoCapable<L::IoType>,
{
let (location, value) = value.into_io_op();
@@ -617,7 +634,7 @@ 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
where
L: IoLoc<T>,
L: IoLoc<Self::Target, T>,
Self: IoCapable<L::IoType>,
F: FnOnce(T) -> T,
{
@@ -656,7 +673,7 @@ fn try_update<T, L, F>(&self, location: L, f: F) -> Result
#[inline(always)]
fn read<T, L>(&self, location: L) -> T
where
L: IoLoc<T>,
L: IoLoc<Self::Target, T>,
Self: IoCapable<L::IoType>,
{
let address = self.io_addr_assert::<L::IoType>(location.offset());
@@ -688,7 +705,7 @@ fn read<T, L>(&self, location: L) -> T
#[inline(always)]
fn write<T, L>(&self, location: L, value: T)
where
L: IoLoc<T>,
L: IoLoc<Self::Target, T>,
Self: IoCapable<L::IoType>,
{
let address = self.io_addr_assert::<L::IoType>(location.offset());
@@ -731,8 +748,8 @@ fn write<T, L>(&self, location: L, value: T)
#[inline(always)]
fn write_reg<T, L, V>(&self, value: V)
where
L: IoLoc<T>,
V: LocatedRegister<Location = L, Value = T>,
L: IoLoc<Self::Target, T>,
V: LocatedRegister<Self::Target, Location = L, Value = T>,
Self: IoCapable<L::IoType>,
{
let (location, value) = value.into_io_op();
@@ -764,8 +781,8 @@ fn write_reg<T, L, V>(&self, value: V)
#[inline(always)]
fn update<T, L, F>(&self, location: L, f: F)
where
L: IoLoc<T>,
Self: IoCapable<L::IoType> + Sized,
L: IoLoc<Self::Target, T>,
Self: IoCapable<L::IoType>,
F: FnOnce(T) -> T,
{
let address = self.io_addr_assert::<L::IoType>(location.offset());

20
rust/kernel/io/register.rs
View File

@@ -113,6 +113,8 @@
io::IoLoc, //
};
use super::Region;
/// Trait implemented by all registers.
pub trait Register: Sized {
/// Backing primitive type of the register.
@@ -129,7 +131,7 @@ pub trait FixedRegister: Register {}
/// Allows `()` to be used as the `location` parameter of [`Io::write`](super::Io::write) when
/// passing a [`FixedRegister`] value.
impl<T> IoLoc<T> for ()
impl<const SIZE: usize, T> IoLoc<Region<SIZE>, T> for ()
where
T: FixedRegister,
{
@@ -143,7 +145,7 @@ fn offset(self) -> usize {
/// A [`FixedRegister`] carries its location in its type. Thus `FixedRegister` values can be used
/// as an [`IoLoc`].
impl<T> IoLoc<T> for T
impl<const SIZE: usize, T> IoLoc<Region<SIZE>, T> for T
where
T: FixedRegister,
{
@@ -168,7 +170,7 @@ pub const fn new() -> Self {
}
}
impl<T> IoLoc<T> for FixedRegisterLoc<T>
impl<const SIZE: usize, T> IoLoc<Region<SIZE>, T> for FixedRegisterLoc<T>
where
T: FixedRegister,
{
@@ -239,7 +241,7 @@ const fn offset(self) -> usize {
}
}
impl<T, B> IoLoc<T> for RelativeRegisterLoc<T, B>
impl<const SIZE: usize, T, B> IoLoc<Region<SIZE>, T> for RelativeRegisterLoc<T, B>
where
T: RelativeRegister,
B: RegisterBase<T::BaseFamily> + ?Sized,
@@ -283,7 +285,7 @@ pub fn try_new(idx: usize) -> Option<Self> {
}
}
impl<T> IoLoc<T> for RegisterArrayLoc<T>
impl<const SIZE: usize, T> IoLoc<Region<SIZE>, T> for RegisterArrayLoc<T>
where
T: RegisterArray,
{
@@ -370,7 +372,7 @@ pub fn try_at(self, idx: usize) -> Option<RelativeRegisterArrayLoc<T, B>> {
}
}
impl<T, B> IoLoc<T> for RelativeRegisterArrayLoc<T, B>
impl<const SIZE: usize, T, B> IoLoc<Region<SIZE>, T> for RelativeRegisterArrayLoc<T, B>
where
T: RelativeRegisterArray,
B: RegisterBase<T::BaseFamily> + ?Sized,
@@ -387,18 +389,18 @@ fn offset(self) -> usize {
/// which to write it.
///
/// Implementors can be used with [`Io::write_reg`](super::Io::write_reg).
pub trait LocatedRegister {
pub trait LocatedRegister<Base: ?Sized> {
/// Register value to write.
type Value: Register;
/// Full location information at which to write the value.
type Location: IoLoc<Self::Value>;
type Location: IoLoc<Base, Self::Value>;
/// Consumes `self` and returns a `(location, value)` tuple describing a valid I/O write
/// operation.
fn into_io_op(self) -> (Self::Location, Self::Value);
}
impl<T> LocatedRegister for T
impl<const SIZE: usize, T> LocatedRegister<Region<SIZE>> for T
where
T: FixedRegister,
{