Re: [PATCH 18/18] gpu: nova-core: firmware: parse `FalconUCodeDescV2` via `zerocopy`

["Danilo Krummrich" <dakr@kernel.org>]

On Tue Jun 2, 2026 at 7:29 PM CEST, Miguel Ojeda wrote:
> Now that we have `zerocopy` support, we can avoid some `unsafe` code.
>
> For instance, for `FalconUCodeDescV2`, we can replace the `unsafe impl
> FromBytes` by safely deriving `zerocopy`'s `FromBytes` and then calling
> `read_from_prefix`.
>
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Acked-by: Danilo Krummrich <dakr@kernel.org>

> ---
>  drivers/gpu/nova-core/firmware.rs | 5 +----
>  drivers/gpu/nova-core/vbios.rs    | 4 ++--
>  2 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
> index 6c2ab69cb605..d97da0c0856d 100644
> --- a/drivers/gpu/nova-core/firmware.rs
> +++ b/drivers/gpu/nova-core/firmware.rs
> @@ -48,7 +48,7 @@ fn request_firmware(
>  
>  /// Structure used to describe some firmwares, notably FWSEC-FRTS.
>  #[repr(C)]
> -#[derive(Debug, Clone)]
> +#[derive(Debug, Clone, zerocopy_derive::FromBytes)]

As discussed, it would be nice to re-export this to avoid the zerocopy_derive.

>  pub(crate) struct FalconUCodeDescV2 {
>      /// Header defined by 'NV_BIT_FALCON_UCODE_DESC_HEADER_VDESC*' in OpenRM.
>      hdr: u32,
> @@ -84,9 +84,6 @@ pub(crate) struct FalconUCodeDescV2 {
>      pub(crate) alt_dmem_load_size: u32,
>  }
>  
> -// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
> -unsafe impl FromBytes for FalconUCodeDescV2 {}
> -
>  /// Structure used to describe some firmwares, notably FWSEC-FRTS.
>  #[repr(C)]
>  #[derive(Debug, Clone)]
> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
> index ebda28e596c5..3f8adfc2e4cf 100644
> --- a/drivers/gpu/nova-core/vbios.rs
> +++ b/drivers/gpu/nova-core/vbios.rs
> @@ -1011,8 +1011,8 @@ pub(crate) fn header(&self) -> Result<FalconUCodeDesc> {
>          let data = self.base.data.get(falcon_ucode_offset..).ok_or(EINVAL)?;
>          match ver {
>              2 => {
> -                let v2 = FalconUCodeDescV2::from_bytes_copy_prefix(data)
> -                    .ok_or(EINVAL)?
> +                let v2 = <FalconUCodeDescV2 as zerocopy::FromBytes>::read_from_prefix(data)

If we import this as

	use zerocopy::FromBytes as _;

we can avoid the qualified syntax and just keep it

	let v2 = FalconUCodeDescV2::read_from_prefix(data)


> +                    .map_err(|_| EINVAL)?
>                      .0;
>                  Ok(FalconUCodeDesc::V2(v2))
>              }
> -- 
> 2.54.0