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

Gary Guo
2026-02-05T15:17:17Z

On Thu Feb 5, 2026 at 2:28 PM GMT, Daniel Almeida wrote:
>
>
>> On 4 Feb 2026, at 12:18, Danilo Krummrich <dakr@kernel.org> wrote:
>>
>> On Wed Feb 4, 2026 at 5:04 AM CET, Link Mauve wrote:
>>> Another option would be to call u32::swap_bytes() on the data being
>>> read/written, but these helpers make the Rust code as ergonomic as the C
>>> code.
>>>
>>> Signed-off-by: Link Mauve <linkmauve@linkmauve.fr>
>>
>> The I/O stuff recently changed quite significantly, please have a look at the
>> driver-core-next branch [1] in the driver-core tree.
>>
>> Also, instead of providing additional *be() methods, we should just create a new
>> type io::Endianness and use it to indicate the device endianness when requesting
>> the I/O resource.
>>
>> For instance, for your driver we could have
>>
>> request.iomap_exclusive_sized::<8>(Endianness::Big)?
>
> Can we please structure this in a way that LittleEndian is the default?
> Perhaps using a const generic that is defaulted, or something along these lines.

I think we should have everything default to little endian, and have wrapper
types that do big endian which require expicit construction, similar to
RelaxedMmio in Alex's series.

Best,
Gary

>
>>
>> and then let the I/O backend choose the correct accessors based on this.
>>
>> I.e. the device is either big or little endian, hence we don't need to provide
>> both accessors at the same time.
>>
>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git/log/?h=driver-core-next
>>