Re: [PATCH 1/7] rust: io: split IoCapable into IoReadable and IoWritable

[Vishal Moola (Fractile)]

On Tue, Oct 20, 2026 at 01:04:03PM +0100, Gary Guo wrote:
> On Thu Oct 15, 2026 at 1:39 PM BST, Daniel Almeida wrote:
> > `IoCapable<T>` provides both `io_read` and `io_write`, so a backend that
> > supports accesses of type `T` supports them in both directions, and every
> > (non-copy) `Io` method that reads or writes a value requires both. There
> > is no way to express a backend, or a view, that can only be read or only
> > be written.
> >
> > Thus, replace `IoCapable<T>` with an `IoReadable<T>` trait holding
> > `io_read` and an `IoWritable<T>` trait holding `io_write`, and implement
> > both for all existing backends. The non-copy `Io` methods that read a
> > value now require `IoReadable` and those that write one require
> > `IoWritable`. `update` and `try_update` read and then write, so they
> > require both.
> >
> > The copy methods use `IoCopyable` and are not changed here.
> >
> > No functional change intended. This prepares for read-only and write-only
> > views, added in a following patch.
> 
> I think by Rust convention these should be named `IoRead`/`IoWrite`, but we've
> aleady named this `IoCapable` and I further made the mistake of adding
> `IoCopyable`...
> 
> So I guess I'm not in a good position to ask for name change, but we should
> consider it. Apart from the name:

IMO the -able part is quite important. As a reader, seeing `IoRead`/`IoWrite`
doesn't tell me enough about what they actually mean on their own.

> Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>
> 
> Best,
> Gary
> 
> >
> > Signed-off-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>
> > ---
> >  rust/kernel/dma.rs    |  12 ++++--
> >  rust/kernel/io.rs     | 101 +++++++++++++++++++++++++++++---------------------
> >  rust/kernel/pci/io.rs |  10 +++--
> >  3 files changed, 75 insertions(+), 48 deletions(-)
>