Re: [PATCH v2 1/4] rust: io: Add big-endian read and write functions

Daniel Almeida
2026-02-08T17:18:55Z

> On 5 Feb 2026, at 19:43, Danilo Krummrich <dakr@kernel.org> wrote:
>
> On Thu Feb 5, 2026 at 11:31 PM CET, Gary Guo wrote:
>> On Thu Feb 5, 2026 at 7:05 PM GMT, Danilo Krummrich wrote:
>>> (1) Devices are either little-endian or big-endian. Hence, having to write
>>>
>>> io.big_endian().write()
>>>
>>> is excessive, we always want big-endian for a big-endian device.
>>
>> You don't need to always write this. You just need to do `big_endian()` once
>> when you obtain the io, and then keep using `BigEndian<Mmio>` instead of just
>> `Mmio`, and the rest of code is still `.write()`.
>
> <snip>
>
>>> (2) It is error prone, if you forget to call big_endian() first, it is a bug.
>>
>> Moot point when `big_endian()` is only done once.
>
> Well, you need to do it at least once per driver entry point. For DRM IOCTLs for
> instance you also have to consider that it is always Devres<Mmio>.
>

Well, this is also the case for relaxed(). I basically made peace with the fact that

let mmio = mmio.relaxed();
< use mmio >

is going to be a reality per driver entrypoint, unless I misunderstood?

— Daniel