rust: io: use view types instead of addresses for `Io`

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 a 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.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20260706-io_projection-v6-9-72cd5d055d54@garyguo.net
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

0 files changed, 0 insertions, 0 deletions