linux.git/rust/kernel/io/mem.rs, branch v7.3-rc2

Merge patch series "rust: I/O type generalization and projection"

2026-07-13T21:50:39+00:00

Gary Guo says:

This series presents a major rework of I/O types, as a summary:

- Make I/O regions typed. The existing untyped region still exists
with a dynamically sized `Region` type.

- Create I/O view types to represent subregion of a full I/O region mapped.
A projection macro is added to allow safely create such subviews.

- Split I/O traits, make I/O views play a central role, avoid
duplicate monomorphization and less `unsafe` code.

- Add a `SysMem` backend, and make `Coherent` implement `Io`.

- Add copying methods (memcpy_{from,to}io and friends).

This series generalize `Mmio` type from just an untyped region to typed
representations (so `MmioRaw` is `__iomem *T`). This allows us to remove
the `IoKnownSize` trait; the information is sourced from just the pointer
from the `KnownSize` trait instead.

Building on top of that, `Mmio` and `ConfigSpace` have been converted to
typed views of I/O regions rather than just a big chunk of untyped I/O
memory. These changes made it possible to implement `Io` trait for
`Coherent`.

Shared system memory, `SysMem` is also added to the series, given it
similarity in implementation compared to `Coherent`. In fact, the series
use `SysMem` to implement `Coherent`'s I/O methods.

Built on these generalization, this series add `io_project!()`.
`io_project!()` performs a safe way to project a bigger view to a small
subviews, and some Nova code has been converted in this series to
demonstrate cleanups possible with this addition.

New `io_read!()`, `io_write!()` has been added that supersedes
`dma_read!()`, `dma_write!()` macro. Although, they work for primitives
only (to be exact, types that the backend is `IoCapable` of).
One feature that was lost from the old `dma_read!()` and `dma_write!()`
series was the ability to read/write a large structs. However, the
semantics was unclear to begin with, as there was no guarantee about their
atomicity even for structs that were small enough to fit in u32.

Suggested-by: Danilo Krummrich
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Generic.20I.2FO.20backends/near/571198078
Link: https://patch.msgid.link/20260706-io_projection-v6-0-72cd5d055d54@garyguo.net
Signed-off-by: Danilo Krummrich

rust: io: mem: return DevresLt from IoMem/ExclusiveIoMem::into_devres()

2026-07-11T17:47:00+00:00

Implement ForLt and CovariantForLt for IoMem<'static, SIZE> and
ExclusiveIoMem<'static, SIZE> so that DevresLt can shorten the stored
'static lifetime back to the caller's borrow lifetime.

CovariantForLt is sound because both types only hold &'a Device,
which is covariant over 'a.

Since DevresLt::new() handles the lifetime transmutation internally,
into_devres() no longer needs an explicit transmute to 'static.

Add DevresIoMem and DevresExclusiveIoMem type aliases.

Reviewed-by: Alexandre Courbot 
Link: https://patch.msgid.link/20260626183630.2585057-8-dakr@kernel.org
[ Add default SIZE parameter to DevresIoMem. - Danilo ]
Signed-off-by: Danilo Krummrich

rust: io: move `Io` methods to extension trait

2026-07-11T16:07:41+00:00

`Io` trait now has a single required method with many more provided
methods. Provided methods may want to rely on their implementations to not
be arbitrarily overridden by implementers for correctness or soundness.
A good example is the `size` method, it may be relied by unsafe code and
thus must be consistent with the metadata obtained from `as_ptr`.

Thus, create a new trait to host `size` method, extract existing provided
methods to the new trait, and provide a blanket implementation. This
pattern is used extensively in userspace Rust libraries e.g. `tokio` where
`AsyncRead` has minimum methods and `AsyncReadExt` is what users mostly
interact with.

To avoid changing all user imports, the base trait is renamed to `IoBase`
and the newly added trait takes the existing `Io` name.

Reviewed-by: Alexandre Courbot 
Suggested-by: Danilo Krummrich 
Signed-off-by: Gary Guo 
Reviewed-by: Daniel Almeida 
Link: https://patch.msgid.link/20260706-io_projection-v6-12-72cd5d055d54@garyguo.net
[ Add comment explaining the purpose of the Io blanket implementation.
  - Danilo ]
Signed-off-by: Danilo Krummrich

rust: io: remove `MmioOwned`

2026-07-11T16:00:12+00:00

`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 
Signed-off-by: Gary Guo 
Reviewed-by: Daniel Almeida 
Suggested-by: Danilo Krummrich 
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Generic.20I.2FO.20backends/near/571198078
Link: https://patch.msgid.link/20260706-io_projection-v6-11-72cd5d055d54@garyguo.net
Signed-off-by: Danilo Krummrich

rust: io: rename `Mmio` to `MmioOwned`

2026-07-11T15:59:32+00:00

Most users would more commonly reach out to a view of `Mmio` rather than an
owned instance of `Mmio`. Only implementor of `Io` like `Bar` or `IoMem`
would need the owned version. Thus, rename `Mmio` to `MmioOwned` so that
the name `Mmio` can be used for the view type instead.

Reviewed-by: Alexandre Courbot 
Signed-off-by: Gary Guo 
Reviewed-by: Daniel Almeida 
Suggested-by: Danilo Krummrich 
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Generic.20I.2FO.20backends/near/571198078
Link: https://patch.msgid.link/20260706-io_projection-v6-6-72cd5d055d54@garyguo.net
Signed-off-by: Danilo Krummrich

rust: io: generalize `MmioRaw` to pointer to arbitrary type

2026-07-11T15:59:32+00:00

Conceptually, `MmioRaw` is just `__iomem *`, so it should work for any
types. Update the existing use case where it represents a region of
compile-time known minimum size and run-time known actual size to use the
dynamic-sized type `Region` instead. Rename `maxsize` method to
reflect that it is the actual size (not a bound) of the region.

Implement `Clone` and `Copy` manually, which cannot be derived due to the
generic parameter. The use of raw pointers also cause the `Send` and `Sync`
auto trait implementation to be lost, so add them back by manual
implementation.

Reviewed-by: Alexandre Courbot 
Signed-off-by: Gary Guo 
Reviewed-by: Daniel Almeida 
Suggested-by: Danilo Krummrich 
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Generic.20I.2FO.20backends/near/571198078
Link: https://patch.msgid.link/20260706-io_projection-v6-5-72cd5d055d54@garyguo.net
Signed-off-by: Danilo Krummrich

rust: io: make IoMem and ExclusiveIoMem lifetime-parameterized

2026-05-27T14:24:28+00:00

Add a lifetime parameter to IoMem<'a, SIZE> and ExclusiveIoMem<'a,
SIZE>, storing a &'a Device reference to tie the mapping to the
device's lifetime.

This mirrors the pci::Bar<'a, SIZE> design and enables drivers to hold
I/O memory mappings directly in their HRT private data, tied to the
device lifetime.

IoRequest::iomap_* methods now return the mapping directly instead of
wrapping it in Devres. Callers that need device-managed revocation can
call the new into_devres() method.

Acked-by: Uwe Kleine-König 
Reviewed-by: Eliot Courtney 
Reviewed-by: Greg Kroah-Hartman 
Reviewed-by: Alexandre Courbot 
Reviewed-by: Gary Guo 
Link: https://patch.msgid.link/20260525202921.124698-20-dakr@kernel.org
Signed-off-by: Danilo Krummrich

rust: platform: make Driver trait lifetime-parameterized

2026-05-27T14:23:31+00:00

Add a 'bound lifetime to the associated Data, changing type Data to type
Data<'bound>.

This allows the driver's bus device private data to capture the device /
driver bound lifetime; device resources can be stored directly by
reference rather than requiring Devres.

The probe() and unbind() callbacks thus gain a 'bound lifetime parameter
on the methods themselves; avoiding a global lifetime on the trait impl.

Existing drivers set type Data<'bound> = Self, preserving the current
behavior.

Acked-by: Uwe Kleine-König 
Reviewed-by: Alexandre Courbot 
Reviewed-by: Greg Kroah-Hartman 
Reviewed-by: Gary Guo 
Link: https://patch.msgid.link/20260525202921.124698-14-dakr@kernel.org
Signed-off-by: Danilo Krummrich

rust: device: make Core and CoreInternal lifetime-parameterized

2026-05-27T14:22:42+00:00

Device references in probe callbacks are scoped to the callback,
not the full binding duration. Add a lifetime parameter to Core and
CoreInternal to accurately represent this in the type system.

Suggested-by: Gary Guo 
Reviewed-by: Greg Kroah-Hartman 
Reviewed-by: Alexandre Courbot 
Reviewed-by: Eliot Courtney 
Reviewed-by: Gary Guo 
Link: https://patch.msgid.link/20260525202921.124698-12-dakr@kernel.org
Signed-off-by: Danilo Krummrich

rust: driver: decouple driver private data from driver type

2026-05-27T14:22:41+00:00

Add a type Data<'bound> associated type to all bus driver traits,
decoupling the driver's bus device private data type from the driver
struct itself.

In the context of adding a 'bound lifetime, making this an associated
type has the advantage that it allows us to avoid a driver trait global
lifetime and it avoids the need for ForLt for bus device private data;
both of which make the subsequent implementation by buses much simpler.

All existing drivers and doc examples set type Data = Self to preserve
the current behavior.

Reviewed-by: Alexandre Courbot 
Reviewed-by: Gary Guo 
Reviewed-by: Greg Kroah-Hartman 
Link: https://patch.msgid.link/20260525202921.124698-5-dakr@kernel.org
Signed-off-by: Danilo Krummrich