On Sun Sep 20, 2026 at 1:38 PM BST, Danilo Krummrich wrote:
> On Sun Sep 20, 2026 at 2:20 PM CEST, Gary Guo wrote:
>> On Fri Sep 18, 2026 at 7:03 PM BST, Alexandre Courbot wrote:
>>> On Thu Sep 17, 2026 at 9:53 AM BST, Gary Guo wrote:
>>>> On Tue Sep 15, 2026 at 8:39 AM BST, Alexandre Courbot wrote:
>>>>> On Wed Sep 2, 2026 at 6:16 PM JST, Eliot Courtney wrote:
>>>>>> Currently, using NonZero/Bounded constants is quite verbose. It's
>>>>>> unfortunate because it disincentivizes using it in interface boundaries.
>>>>>> Introduce a macro to make it nicer to use. The macro `cv!` (for constant
>>>>>> value) takes a const integer expression and widens it to i128 (at build
>>>>>> time only) before passing it as a const generic value to a new trait
>>>>>> `FromConst`. The value is then converted and appears in the
>>>>>> associated constant `FromConst::VALUE`. The trait is implemented by
>>>>>> NonZero, Bounded, and Alignment and lets values of each be constructed
>>>>>> from constants without a verbose turbofish syntax.
>>>>>> For example, `const { NonZero::new(1).unwrap() }` can be written as
>>>>>> `cv!(1)`.
>>>>>>
>>>>>> Suggested-by: Gary Guo <[email protected]>
>>>>>> Signed-off-by: Eliot Courtney <[email protected]>
>>>>>
>>>>> I don't think we have any user but nova-core at the moment, and it
>>>>> benefits from this in several series (patch 3 here, but also ID pool and
>>>>> later r000). Miguel, is this ok if we take it (i.e. the next revision)
>>>>> through drm-rust-next?
>>>>
>>>> How about a topic tag shared between Rust and drm-rust-next? We could also
>>>> remove the old num casts API as part of topic tag and fix all existing
>>>> users as
>>>> part of merge.
>>>
>>> Not opposed to the idea but IIRC there was already some pushback to the
>>> idea. There doesn't seem to be an urgency to remove the old num casts
>>> API that justifies doing it now with a more complicated merge path.
>>
>> Sorry, what pushbacks? I thought that `cv!` is what everyone agrees on. I
>> see no
>> downside of this compared to the turbofish const conversion APIs.
>>
>> I am not opposed to delaying removal for the next cycle, but IMO the `cv!`
>> macro
>> should be present on Rust tree so it's visible and improvements can be made
>> from
>> there, so I think we should do a topic tag regardless whether the old API
>> removal happens or not.
>
> I think Alex refers to this thread [1]; there's was some more context to this
> though.
Right, so "pushback" here relates to the logistics of old API removal, not the
idea of `cv!`?
Best,
Gary
>
> [1] https://lore.kernel.org/all/[email protected]/
