Re: [PATCH v5 09/20] rust: io: use view types instead of addresses for `Io`

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

On Fri Jun 26, 2026 at 11:45 PM JST, Gary Guo wrote:
> Currently, `io_read` and `io_write` methods require the exact type of `Io`
> plus an address. This means that they need to be monomorphized for each
> different `Io` instance. This also means that multiple I/O implementors for
> the same I/O kind needs to duplicate implementation (e.g. `Mmio` and
> `MmioOwned`).
>
> Create a new `IoBackend` trait and define these operations on it instead.
> The operations are just going to receive a view type and operate on them.
> This has the additional advantage that the invariants can be moved from the
> trait (and guaranteed via `unsafe`) to type invariants on the canonical
> view types of the backends, so `io_read` and `io_write` can be safe.
>
> Note that view type is needed; addresses are insufficient in this
> design, as they do not carry sufficient information. For example,
> `ConfigSpace` needs `&pci::Device` in addition to the address.
>
> `io_addr_assert` and `io_addr` are renamed to `io_view*` to reflect
> that they operate on views now, and make them standalone functions so
> they cannot be used by users to cast types outside io.rs.

The extraction as standalone functions could have been its own patch so
as to not distract from the meat of this one (and make the diff of the
functional changes introduced by this patch to these functions easier to
review), but regardless:

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