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

Gary Guo <gary@garyguo.net> 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<T>` 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<T>`.

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 <dakr@kernel.org>
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 <dakr@kernel.org>

1 files changed, 12 insertions, 12 deletions

diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
index b7c075a39ba4..20f94030f977 100644
--- a/rust/kernel/devres.rs
+++ b/rust/kernel/devres.rs
@@ -70,17 +70,19 @@ struct Inner<T> {
 ///     devres::Devres,
 ///     io::{
 ///         Io,
-///         IoKnownSize,
+///         IoBase,
 ///         Mmio,
 ///         MmioRaw,
-///         PhysAddr, //
+///         MmioBackend,
+///         PhysAddr,
+///         Region, //
 ///     },
 ///     prelude::*,
 /// };
 /// use core::ops::Deref;
 ///
 /// // See also [`pci::Bar`] for a real example.
-/// struct IoMem<const SIZE: usize>(MmioRaw<SIZE>);
+/// struct IoMem<const SIZE: usize>(MmioRaw<Region<SIZE>>);
 ///
 /// impl<const SIZE: usize> IoMem<SIZE> {
 ///     /// # Safety
@@ -95,7 +97,7 @@ struct Inner<T> {
 ///             return Err(ENOMEM);
 ///         }
 ///
-///         Ok(IoMem(MmioRaw::new(addr as usize, SIZE)?))
+///         Ok(IoMem(MmioRaw::new_region(addr as usize, SIZE)?))
 ///     }
 /// }
 ///
@@ -106,12 +108,13 @@ struct Inner<T> {
 ///     }
 /// }
 ///
-/// impl<const SIZE: usize> Deref for IoMem<SIZE> {
-///    type Target = Mmio<SIZE>;
+/// impl<'a, const SIZE: usize> IoBase<'a> for &'a IoMem<SIZE> {
+///    type Backend = MmioBackend;
+///    type Target = Region<SIZE>;
 ///
-///    fn deref(&self) -> &Self::Target {
+///    fn as_view(self) -> Mmio<'a, Region<SIZE>> {
 ///         // SAFETY: The memory range stored in `self` has been properly mapped in `Self::new`.
-///         unsafe { Mmio::from_raw(&self.0) }
+///         unsafe { Mmio::from_raw(self.0) }
 ///    }
 /// }
 /// # fn no_run(dev: &Device<Bound>) -> Result<(), Error> {
@@ -299,10 +302,7 @@ impl<T: Send + 'static> Devres<T> {
     /// use kernel::{
     ///     device::Core,
     ///     devres::Devres,
-    ///     io::{
-    ///         Io,
-    ///         IoKnownSize, //
-    ///     },
+    ///     io::Io,
     ///     pci, //
     /// };
     ///