Re: [PATCH v3 0/6] gpu: nova-core: remove use of `as` for integer conversions

["Alexandre Courbot" <acourbot@nvidia.com>]

On Wed Oct 29, 2025 at 8:12 AM JST, Alexandre Courbot wrote:
> Using the `as` operator for integer conversions is discouraged, as it
> silently strips data if the destination type is smaller than the source.
> Many such conversions can be replaced with `from`/`into` or (when
> justified) `try_from`/`try_into`, but these traits cannot unfortunately
> cover all conversions satisfyingly.
>
> There is for instance the case of converting a `usize` to `u64`, which,
> in the case of the kernel today, is completely lossless but cannot be
> done because the Rust standard library does not provide a `From`
> implementation for conversions that are not future-proof.
>
> Still, in the kernel it is very practical to be able to perform such
> conversions when they are safe to do for the current build target.
>
> This patchset tries to eradicate the use of `as` in nova-core, by using
> existing means and introducing new ones.
>
> The first 4 patches use the already-available `From` and `TryFrom` trait
> where it is possible or advisable.
>
> The fifth patch introduces a new module that proposes conversion
> functions for those that are infallible under the current build target.
> This is done through a set of const functions, and the `FromSafeCast`
> and `IntoSafeCast` extension traits which, as their names lightly
> suggest, offer conversion for those types on which the `as` operator can
> be used losslessly.
>
> This new module is put to use in the sixth patch.
>
> The idea was first suggested by Danilo.
>
> As Danilo suggested, this could eventually find its place in the kernel
> crate if the implementation is deemed to be fit, but for now let's
> review and let it mature in nova-core.

All patches pushed to drm-rust-next, thanks!