[PATCH v2 1/5] gpu: nova-core: use checked arithmetic in FWSEC firmware parsing

[Danilo Krummrich]

On Mon Jan 26, 2026 at 9:23 PM CET, Joel Fernandes wrote:
> @@ -267,7 +264,12 @@ fn new_fwsec(dev: &Device<device::Bound>, bios: &Vbios, cmd: FwsecCommand) -> Re
>          let ucode = bios.fwsec_image().ucode(&desc)?;
>          let mut dma_object = DmaObject::from_data(dev, ucode)?;
>  
> -        let hdr_offset = usize::from_safe_cast(desc.imem_load_size() + desc.interface_offset());
> +        // Compute hdr_offset = imem_load_size + interface_offset.

I do get the idea behind those comments, but are we sure that's really a good
idea? How do we ensure to keep them up to date in case we have to change the
code?

If we really want this, I'd at least chose a common syntax, e.g.

	// CALC: `imem_load_size + interface_offset`

without the variable name the resulting value is assigned to.

But I'd rather prefer to just drop those comments.

> +        let hdr_offset = desc
> +            .imem_load_size()
> +            .checked_add(desc.interface_offset())
> +            .map(usize::from_safe_cast)
> +            .ok_or(EINVAL)?;
>          // SAFETY: we have exclusive access to `dma_object`.
>          let hdr: &FalconAppifHdrV1 = unsafe { transmute(&dma_object, hdr_offset) }?;