[PATCH RFC 1/3] rust: add useful ops for u64

[Alexandre Courbot]

On Wed Feb 19, 2025 at 12:24 PM JST, John Hubbard wrote:
> On 2/18/25 5:21 PM, Alexandre Courbot wrote:
>> On Wed Feb 19, 2025 at 5:51 AM JST, Timur Tabi wrote:
>>> On Tue, 2025-02-18 at 22:16 +0900, Alexandre Courbot wrote:
> ...
>> More likely this would be something like:
>> 
>>    let SplitU64 { high: some_u32, .. } = some_u64;
>> 
>> Which is still a bit verbose, but a single-liner.
>> 
>> Actually. How about adding methods to this trait that return either
>> component?
>> 
>>    let some_u32 = some_u64.high_half();
>>    let another_u32 = some_u64.low_half();
>> 
>> These should be used most of the times, and using destructuring/tuple
>> would only be useful for a few select cases.
>
> I think I like this approach best so far, because that is actually how
> drivers tend to use these values: one or the other 32 bits at a time.
> Registers are often grouped into 32-bit named registers, and driver code
> wants to refer to them one at a time (before breaking some of them down
> into smaller named fields)>
>
> The .high_half() and .low_half() approach matches that very closely.
> And it's simpler to read than the SplitU64 API, without losing anything
> we need, right?

Yes, that looks like the optimal way to do this actually. It also
doesn't introduce any overhead as the destructuring was doing both
high_half() and low_half() in sequence, so in some cases it might
even be more efficient.

I'd just like to find a better naming. high() and low() might be enough?
Or are there other suggestions?