Re: [PATCH v2 4/5] drm/nova: use `zerocopy` in bootloader.rs

[Alistair Popple <apopple@nvidia.com>]

On 2026-07-02 at 22:03 +1000, Pedro Yudi Honda <niyudi.honda@usp.br> wrote...
> From: Pedro Yudi Honda <niyudi.honda@usp.br>
> 
> In firmware/fwsec/bootloader.rs, replace the following `transmute`
> traits with their `zerocopy` equivalents:
> 
> - `transmute::FromBytes` -> `zerocopy::FromBytes`
> - `transmute::AsBytes` -> `zerocopy::IntoBytes`
> - add `zerocopy::Immutable` where necessary
> 
> Update call sites accordingly.

Reviewed-by: Alistair Popple <apopple@nvidia.com>

> 
> Signed-off-by: Pedro Yudi Honda <niyudi.honda@usp.br>
> ---
>  .../gpu/nova-core/firmware/fwsec/bootloader.rs | 18 ++++--------------
>  1 file changed, 4 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> index 66b9f4d1b41c..03d3090bd9ef 100644
> --- a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> +++ b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> @@ -18,15 +18,9 @@
>          Alignable,
>          Alignment, //
>      },
> -    sizes,
> -    transmute::{
> -        AsBytes,
> -        FromBytes, //
> -    },
> +    sizes, //
>  };
>  
> -use zerocopy::FromBytes as _;
> -
>  use crate::{
>      driver::Bar0,
>      falcon::{
> @@ -57,7 +51,7 @@
>  ///
>  /// Most of its fields appear to be legacy and carry incorrect values, so they are left unused.
>  #[repr(C)]
> -#[derive(Debug, Clone)]
> +#[derive(Debug, Clone, FromBytes)]
>  struct BootloaderDesc {
>      /// Starting tag of bootloader.
>      start_tag: u32,
> @@ -73,15 +67,13 @@ struct BootloaderDesc {
>      /// Size of data section in the image. Unused as we build the data section ourselves.
>      _data_size: u32,
>  }
> -// SAFETY: any byte sequence is valid for this struct.
> -unsafe impl FromBytes for BootloaderDesc {}
>  
>  /// Structure used by the boot-loader to load the rest of the code.
>  ///
>  /// This has to be filled by the GPU driver and copied into DMEM at offset
>  /// [`BootloaderDesc.dmem_load_off`].
>  #[repr(C, packed)]
> -#[derive(Debug, Clone)]
> +#[derive(Debug, Clone, IntoBytes, zerocopy_derive::Immutable)]
>  struct BootloaderDmemDescV2 {
>      /// Reserved, should always be first element.
>      reserved: [u32; 4],
> @@ -120,8 +112,6 @@ struct BootloaderDmemDescV2 {
>      /// Arguments to be passed to the target firmware being loaded.
>      argv: u32,
>  }
> -// SAFETY: This struct doesn't contain uninitialized bytes and doesn't have interior mutability.
> -unsafe impl AsBytes for BootloaderDmemDescV2 {}
>  
>  /// Wrapper for [`FwsecFirmware`] that includes the bootloader performing the actual load
>  /// operation.
> @@ -160,7 +150,7 @@ pub(crate) fn new(
>  
>              fw.data()
>                  .get(desc_offset..)
> -                .and_then(BootloaderDesc::from_bytes_copy_prefix)
> +                .and_then(|b| BootloaderDesc::read_from_prefix(b).ok())
>                  .ok_or(EINVAL)?
>                  .0
>          };
> -- 
> 2.34.1
>