Re: [PATCH v5 01/20] rust: io: add dynamically-sized `Region` type

["Alexandre Courbot" <acourbot@nvidia.com>]

On Fri Jun 26, 2026 at 11:45 PM JST, Gary Guo wrote:
<...>
> diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
> index fcc7678fd9e3..d1c5f0121994 100644
> --- a/rust/kernel/io.rs
> +++ b/rust/kernel/io.rs
> @@ -6,7 +6,11 @@
>  
>  use crate::{
>      bindings,
> -    prelude::*, //
> +    prelude::*,
> +    ptr::{
> +        Alignment,
> +        KnownSize, //
> +    }, //
>  };
>  
>  pub mod mem;
> @@ -31,6 +35,57 @@
>  /// `CONFIG_PHYS_ADDR_T_64BIT`, and it can be a u64 even on 32-bit architectures.
>  pub type ResourceSize = bindings::resource_size_t;
>  
> +/// Untyped I/O region.
> +///
> +/// This type can be used when an I/O region without known type information has a compile-time known
> +/// minimum size (and a runtime known actual size).
> +///
> +/// # Invariants
> +///
> +/// - Size of the region is at least as large as the `SIZE` generic parameter.
> +/// - Size of the region is multiple of 4.
> +#[repr(C, align(4))]
> +pub struct Region<const SIZE: usize = 0> {
> +    inner: [u8],
> +}
> +
> +impl<const SIZE: usize> Region<SIZE> {
> +    /// Create a raw mutable pointer from given base address and size.
> +    ///
> +    /// `size` should be at least as large as the minimum size `SIZE`, and `base` and `size` should
> +    /// be 4-byte aligned to uphold the type invariant.

The second part of my comment on v4 was not relevant [1], but how about the
"should -> must" proposal?

Regardless:

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

[1] https://lore.kernel.org/all/DJ9JE3I9MCG2.2G88FWQPWRBH3@garyguo.net/