Re: [PATCH v6 5/9] rust: io: add IoRef and IoWrite types

[Alexandre Courbot]

On Mon Feb 16, 2026 at 7:35 PM JST, Alice Ryhl wrote:
> On Mon, Feb 16, 2026 at 06:36:29PM +0900, Alexandre Courbot wrote:
>> On Mon Feb 16, 2026 at 6:01 PM JST, Alice Ryhl wrote:
>> > On Mon, Feb 16, 2026 at 05:04:41PM +0900, Alexandre Courbot wrote:
>> >> I/O accesses are defined by the following properties:
>> >> 
>> >> - For reads, a start address, a width, and a type to interpret the read
>> >>   value as,
>> >> - For writes, the same as above, and a value to write.
>> >> 
>> >> Introduce the `IoRef` trait, which allows implementing types to specify
>> >> the address a type expects to be accessed at, as well as the width of
>> >> the access, and the user-facing type used to perform the access.
>> >> 
>> >> This allows read operations to be made generic with the `read` method
>> >> over an `IoRef` argument.
>> >> 
>> >> Write operations need a value to write on top of the `IoRef`: fulfill
>> >> that purpose with the `IoWrite`, which is the combination of an `IoRef`
>> >> and a value of the type it expects. This allows write operations to be
>> >> made generic with the `write` method over a single `IoWrite` argument.
>> >> 
>> >> The main purpose of these new entities is to allow register types to be
>> >> written using these generic `read` and `write` methods of `Io`.
>> >> 
>> >> Co-developed-by: Gary Guo <gary@xxxxxxxxxxx>
>> >> Signed-off-by: Gary Guo <gary@xxxxxxxxxxx>
>> >> Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
>> >> ---
>> >>  rust/kernel/io.rs | 243 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> >>  1 file changed, 243 insertions(+)
>> >> 
>> >> diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
>> >> index b150743ffa4f..6da8593f7858 100644
>> >> --- a/rust/kernel/io.rs
>> >> +++ b/rust/kernel/io.rs
>> >> @@ -173,6 +173,160 @@ pub trait IoCapable<T> {
>> >>      unsafe fn io_write(&self, value: T, address: usize);
>> >>  }
>> >>  
>> >> +/// Reference to an I/O location, describing the offset, width, and return type of an access.
>> >
>> > In the next patch you implement this for usize, but here you say it's a
>> > reference to an I/O location. I'm pretty sure usize is not a reference
>> > to an I/O location.
>> 
>> Methods like `read_u8` use a `usize` to reference the location we want
>> to read, so aren't they in that context?
>
> Oh .. I wouldn't use the word "reference" like that. How about "index"
> instead?

"index" looks more accurate indeed for something that is not a pointer
type.