Re: [RFC PATCH v4 1/3] i2c: rust: implement SMBus read abstraction via kernel::io::Io for I2cClient

On Sat, 11 Jul 2026 at 17:05, Igor Korotin <[email protected]> wrote:

> This driver only calls try_read8()/try_read16(), so AS5600 itself isn't
> affected in practice. But the abstraction being introduced here would be
> unsound the moment any write-capable consumer reaches for it -- and I
> don't think patching try_write8/try_update one at a time is the right
> fix, since it just leaves the same trap for whichever method nobody's
> gotten around to overriding yet.
>
> Danilo -- since using Io for I2C was originally your suggestion, I'd like
> your read on this before we go further: IoCapable::io_read/io_write are
> infallible by signature, which holds for MMIO/PCI-config (bounds-checked
> implies success) but doesn't hold for a bus transaction -- I2C can
> genuinely fail per-transfer regardless of address validity. Given that,
> is Io/IoCapable the right abstraction for I2cClient to implement at all,
> or does I2C need its own fallible-native interface rather than overriding
> pieces of this one?


Agreed. I will rework on top of Danilo's FallibleIoCapable approach
in v5. I checked rust-next and neither FallibleIoCapable nor
io_projection v6 has landed yet.

Danilo, should I wait for io_projection to land first before rebasing,
or should I carry FallibleIoCapable as a preparatory patch in my series?

Thanks for the detailed review.

Coirul