linux-kernel - Re: [PATCH RFC 1/3] rust: add useful ops for u64

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Message-Id: <D7Y3CO9OMZBQ.1QGFV73NZBBIF@nvidia.com>
Date: Fri, 21 Feb 2025 20:35:54 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "John Hubbard" <jhubbard@...dia.com>, "Daniel Almeida"
 <daniel.almeida@...labora.com>, "Dave Airlie" <airlied@...il.com>
Cc: "Timur Tabi" <ttabi@...dia.com>, "dri-devel@...ts.freedesktop.org"
 <dri-devel@...ts.freedesktop.org>, "rust-for-linux@...r.kernel.org"
 <rust-for-linux@...r.kernel.org>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>, "nouveau@...ts.freedesktop.org"
 <nouveau@...ts.freedesktop.org>, "dakr@...nel.org" <dakr@...nel.org>, "Ben
 Skeggs" <bskeggs@...dia.com>, "Nouveau"
 <nouveau-bounces@...ts.freedesktop.org>
Subject: Re: [PATCH RFC 1/3] rust: add useful ops for u64

On Thu Feb 20, 2025 at 9:14 AM JST, John Hubbard wrote:
> On 2/19/25 3:13 PM, Daniel Almeida wrote:
>>> On 19 Feb 2025, at 17:23, Dave Airlie <airlied@...il.com> wrote:
>>> On Thu, 20 Feb 2025 at 06:22, John Hubbard <jhubbard@...dia.com> wrote:
>>>> On 2/19/25 4:51 AM, Alexandre Courbot wrote:
>>>>> 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?
>>>>>
>>>>
>>>> Maybe use "32" instead of "half":
>>>>
>>>>      .high_32()  / .low_32()
>>>>      .upper_32() / .lower_32()
>>>>
>>>
>>> The C code currently does upper_32_bits and lower_32_bits, do we want
>>> to align or diverge here?
>
> This sounds like a trick question, so I'm going to go with..."align". haha :)
>
>>>
>>> Dave.
>> 
>> 
>> My humble suggestion here is to use the same nomenclature. `upper_32_bits` and
>> `lower_32_bits` immediately and succinctly informs the reader of what is going on.
>> 
>
> Yes. I missed the pre-existing naming in C, but since we have it and it's
> well-named as well, definitely this is the way to go.

Agreed, I wasn't aware of the C equivalents either, but since they exist
we should definitely use the same naming scheme.