kernel/linux.git/drivers/gpu/nova-core/num.rs, branch v6.19.11

gpu: nova-core: num: add functions to safely convert a const value to a smaller type

2025-11-14T11:25:15+00:00

There are times where we need to store a constant value defined as a larger type (e.g. through a binding) into a smaller type, knowing that the value will fit. Rust, unfortunately, only provides us with the `as` operator for that purpose, the use of which is discouraged as it silently strips data. Extend the `num` module with functions allowing to perform the conversion infallibly, at compile time. Example: const FOO_VALUE: u32 = 1; // `FOO_VALUE` fits into a `u8`, so the conversion is valid. let foo = num::u32_to_u8::<{ FOO_VALUE }>(); We are going to use this feature extensively in Nova. Reviewed-by: Mikko Perttunen [acourbot@nvidia.com: fix mistake in example pointed out by Mikko.] Signed-off-by: Alexandre Courbot Message-ID: <20251110-gsp_boot-v9-3-8ae4058e3c0e@nvidia.com>

gpu: nova-core: replace use of `as` with functions from `num`

2025-11-07T23:22:45+00:00

Use the newly-introduced `num` module to replace the use of `as` wherever it is safe to do. This ensures that a given conversion cannot lose data if its source or destination type ever changes. Acked-by: Danilo Krummrich [acourbot@nvidia.com: fix merge conflicts after rebase.] Signed-off-by: Alexandre Courbot Message-ID: <20251029-nova-as-v3-5-6a30c7333ad9@nvidia.com>

gpu: nova-core: add functions and traits for lossless integer conversions

2025-11-07T23:22:36+00:00

The core library's `From` implementations do not cover conversions that are not portable or future-proof. For instance, even though it is safe today, `From` is not implemented for `u64` because of the possibility to support larger-than-64bit architectures in the future. However, the kernel supports a narrower set of architectures, and in the case of Nova we only support 64-bit. This makes it helpful and desirable to provide more infallible conversions, lest we need to rely on the `as` keyword and carry the risk of silently losing data. Thus, introduce a new module `num` that provides safe const functions performing more conversions allowed by the build target, as well as `FromSafeCast` and `IntoSafeCast` traits that are just extensions of `From` and `Into` to conversions that are known to be lossless. Suggested-by: Danilo Krummrich Link: https://lore.kernel.org/rust-for-linux/DDK4KADWJHMG.1FUPL3SDR26XF@kernel.org/ Acked-by: Danilo Krummrich [acourbot@nvidia.com: fix merge conflicts after rebase.] Signed-off-by: Alexandre Courbot Message-ID: <20251029-nova-as-v3-4-6a30c7333ad9@nvidia.com>