linux-kernel - Re: [PATCH 5/7] gpu: nova-core: add extra conversion functions and traits

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Message-Id: <DDUB9FJY8IRH.1M5GHVSOFCR3Q@nvidia.com>
Date: Wed, 29 Oct 2025 07:32:59 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "John Hubbard" <jhubbard@...dia.com>, "Miguel Ojeda"
 <miguel.ojeda.sandonis@...il.com>
Cc: "Alice Ryhl" <aliceryhl@...gle.com>, "David Airlie" <airlied@...il.com>,
 "Simona Vetter" <simona@...ll.ch>, "Miguel Ojeda" <ojeda@...nel.org>, "Alex
 Gaynor" <alex.gaynor@...il.com>, "Boqun Feng" <boqun.feng@...il.com>, "Gary
 Guo" <gary@...yguo.net>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, "Benno Lossin" <lossin@...nel.org>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Trevor Gross" <tmgross@...ch.edu>,
 "Alistair Popple" <apopple@...dia.com>, "Joel Fernandes"
 <joelagnelf@...dia.com>, "Timur Tabi" <ttabi@...dia.com>, "Edwin Peer"
 <epeer@...dia.com>, <nouveau@...ts.freedesktop.org>,
 <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, "Danilo Krummrich" <dakr@...nel.org>,
 "Matthew Wilcox" <willy@...radead.org>, "Nouveau"
 <nouveau-bounces@...ts.freedesktop.org>
Subject: Re: [PATCH 5/7] gpu: nova-core: add extra conversion functions and
 traits

On Wed Oct 29, 2025 at 2:18 AM JST, John Hubbard wrote:
> On 10/28/25 7:44 AM, Alexandre Courbot wrote:
>> On Tue Oct 28, 2025 at 3:46 AM JST, John Hubbard wrote:
>>> On 10/26/25 9:44 AM, Miguel Ojeda wrote:
>>>> On Sun, Oct 26, 2025 at 3:40 PM Alexandre Courbot <acourbot@...dia.com> wrote:
>>> ...
>>>
>>>> Regarding the `.into_as()` name, it makes sense, but it can be a bit
>>>> surprising when reading out of context... The standalone functions are
>>>> super clear, in comparison. But I am not sure what could be better.
>>>> `into_in_this_arch()` or similar could emphasize that this will only
>>>> work in certain architectures, i.e. it is "an `into()` for this arch"
>>>> rather than the general one.
>>>> That would go well with the idea that you didn't implement it for
>>>> other obvious types, which I guess was to avoid developers using this
>>>> instead of `into()` by mistake, right?
>>>>
>>>
>>> Exactly: the into-as, from-as naming suffers from *appearing* to be
>>> familiar and readable, but actually, the naming gives no hint as to
>>> what it is really doing--nor how it is subtly different from the
>>> basic from/as/into standard conversions.
>>>
>>> Instead, we need to add something (almost anything) to the name, to
>>> make it clearly different from the from/as/into.
>>>
>>> into_for_arch() goes in that direction, for example.
>> 
>> I'd like to get more input on that, for I am not sure how we can stay
>> succint in the naming, while carrying the relevant information.
>
> That's too many constraints: if you want an extremely short name
> that carries information, *and* avoids (as requested here) confusion
> with existing "as" methods, then...you can't.
>
> But you are allowed to be less succinct here, because the more
> specialized and rare a case is, the longer you can make the name.
> And here, you are definitely allowed a few more characters.
>
>
>> `into_arch` does not sound much more explanatory than `into_as` - the
>> intent with the latter was to say "I would normally have done an `as`,
>> but instead here is a method that attests that this operations is indeed
>> lossless and safe".
>> 
>> The best naming scheme I could think of is to have the methods carry the
>> source or destination types: e.g. `from_usize` or `into_usize` (like the
>> standalone functions), but that would require defining as many traits,
>> and increase the number of imports - if we go that way, we might just as
>> well drop the traits completely and use the standalone functions.
>
> Accurate names are really desirable; maybe we shouldn't completely
> close the door to the above approach.

I think we have reached the stage where any responsible adult would
shove this whole discussion into a LLM and see what it comes up with.

And the candidate is... `FromSafeCast`/`IntoSafeCast`. Which I have to
say sounds like a good middle ground? :) The intent is definitely to
perform a safe cast here.