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

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<SIZE>` 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 <acourbot@nvidia.com>
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
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-v6-5-72cd5d055d54@garyguo.net
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
index ed30ccc6e68e..d0c677fd7932 100644
--- a/rust/kernel/devres.rs
+++ b/rust/kernel/devres.rs
@@ -70,14 +70,15 @@ struct Inner<T> {
 ///         Io,
 ///         Mmio,
 ///         MmioRaw,
-///         PhysAddr, //
+///         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
@@ -92,7 +93,7 @@ struct Inner<T> {
 ///             return Err(ENOMEM);
 ///         }
 ///
-///         Ok(IoMem(MmioRaw::new(addr as usize, SIZE)?))
+///         Ok(IoMem(MmioRaw::new_region(addr as usize, SIZE)?))
 ///     }
 /// }
 ///