Re: [PATCH v12 2/5] rust: io: separate generic I/O helpers from MMIO implementation

["Danilo Krummrich" <dakr@kernel.org>]

(Cc: Uwe, Michal)

On Wed Jan 21, 2026 at 9:22 PM CET, Zhi Wang wrote:
> The previous Io<SIZE> type combined both the generic I/O access helpers
> and MMIO implementation details in a single struct. This coupling prevented
> reusing the I/O helpers for other backends, such as PCI configuration
> space.
>
> Establish a clean separation between the I/O interface and concrete
> backends by separating generic I/O helpers from MMIO implementation.
>
> Introduce a new trait hierarchy to handle different access capabilities:
>
> - IoCapable<T>: A marker trait indicating that a backend supports I/O
>   operations of a certain type (u8, u16, u32, or u64).
>
> - Io trait: Defines fallible (try_read8, try_write8, etc.) and infallibile
>   (read8, write8, etc.) I/O methods with runtime bounds checking and
>   compile-time bounds checking.
>
> - IoKnownSize trait: The marker trait for types support infallible I/O
>   methods.
>
> Move the MMIO-specific logic into a dedicated Mmio<SIZE> type that
> implements the Io traits. Rename IoRaw to MmioRaw and update consumers to
> use the new types.
>
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Alice Ryhl <aliceryhl@google.com>
> Cc: Bjorn Helgaas <helgaas@kernel.org>
> Cc: Gary Guo <gary@garyguo.net>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Zhi Wang <zhiw@nvidia.com>
> ---
>  drivers/gpu/drm/tyr/regs.rs            |   1 +
>  drivers/gpu/nova-core/gsp/sequencer.rs |   5 +-
>  drivers/gpu/nova-core/regs/macros.rs   |  90 +++---
>  drivers/gpu/nova-core/vbios.rs         |   1 +
>  drivers/pwm/pwm_th1520.rs              |   5 +-
>  rust/kernel/devres.rs                  |  19 +-
>  rust/kernel/io.rs                      | 398 ++++++++++++++++++++-----
>  rust/kernel/io/mem.rs                  |  16 +-
>  rust/kernel/io/poll.rs                 |  16 +-
>  rust/kernel/pci/io.rs                  |  12 +-
>  samples/rust/rust_driver_pci.rs        |   1 +
>  11 files changed, 433 insertions(+), 131 deletions(-)

<snip>

> diff --git a/drivers/pwm/pwm_th1520.rs b/drivers/pwm/pwm_th1520.rs
> index e3b7e77356fc..616ca398b2c5 100644
> --- a/drivers/pwm/pwm_th1520.rs
> +++ b/drivers/pwm/pwm_th1520.rs
> @@ -26,7 +26,10 @@
>      clk::Clk,
>      device::{Bound, Core, Device},
>      devres,
> -    io::mem::IoMem,
> +    io::{
> +        mem::IoMem,
> +        Io, //
> +    },
>      of, platform,
>      prelude::*,
>      pwm, time,