Re: [PATCH v2 2/5] drm/nova: use `zerocopy` in booter.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/booter.rs, replace the following `transmute` traits with
> their `zerocopy` equivalents:
> 
> - `transmute::FromBytes` -> `zerocopy::FromBytes`

Having a single item list reads a bit strange to me. I'd just say "replace
`transmute::FromBytes` with `zerocopy::FromBytes`" and if you want to list the
types it's replaced for you could. But that's a bit superfluous as it's clear
from the patch anyway.

But that's a small nit really, everything looks ok to me so feel free to add:

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

> Update call sites accordingly.
>
> Signed-off-by: Pedro Yudi Honda <niyudi.honda@usp.br>
> ---
>  drivers/gpu/nova-core/firmware/booter.rs | 26 +++++++-----------------
>  1 file changed, 7 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/firmware/booter.rs b/drivers/gpu/nova-core/firmware/booter.rs
> index acb7f4d8a532..fe9389b84b90 100644
> --- a/drivers/gpu/nova-core/firmware/booter.rs
> +++ b/drivers/gpu/nova-core/firmware/booter.rs
> @@ -10,8 +10,7 @@
>  use kernel::{
>      device,
>      dma::Coherent,
> -    prelude::*,
> -    transmute::FromBytes, //
> +    prelude::*, //
>  };
>  
>  use crate::{
> @@ -43,7 +42,7 @@ fn frombytes_at<S: FromBytes + Sized>(slice: &[u8], offset: usize) -> Result<S>
>      let end = offset.checked_add(size_of::<S>()).ok_or(EINVAL)?;
>      slice
>          .get(offset..end)
> -        .and_then(S::from_bytes_copy)
> +        .and_then(|b| S::read_from_bytes(b).ok())
>          .ok_or(EINVAL)
>  }
>  
> @@ -52,7 +51,7 @@ fn frombytes_at<S: FromBytes + Sized>(slice: &[u8], offset: usize) -> Result<S>
>  /// Such firmwares have an application-specific payload that needs to be patched with a given
>  /// signature.
>  #[repr(C)]
> -#[derive(Debug, Clone)]
> +#[derive(Debug, Clone, FromBytes)]
>  struct HsHeaderV2 {
>      /// Offset to the start of the signatures.
>      sig_prod_offset: u32,
> @@ -75,9 +74,6 @@ struct HsHeaderV2 {
>      header_size: u32,
>  }
>  
> -// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
> -unsafe impl FromBytes for HsHeaderV2 {}
> -
>  /// Heavy-Secured Firmware image container.
>  ///
>  /// This provides convenient access to the fields of [`HsHeaderV2`] that are actually indices to
> @@ -144,6 +140,7 @@ fn signatures_iter(&'a self) -> Result<impl Iterator<Item = BooterSignature<'a>>
>  
>  /// Signature parameters, as defined in the firmware.
>  #[repr(C)]
> +#[derive(FromBytes)]
>  struct HsSignatureParams {
>      /// Fuse version to use.
>      fuse_ver: u32,
> @@ -153,9 +150,6 @@ struct HsSignatureParams {
>      ucode_id: u32,
>  }
>  
> -// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
> -unsafe impl FromBytes for HsSignatureParams {}
> -
>  impl HsSignatureParams {
>      /// Returns the signature parameters contained in `hs_fw`.
>      ///
> @@ -170,14 +164,14 @@ fn new(hs_fw: &HsFirmwareV2<'_>) -> Result<Self> {
>          hs_fw
>              .fw
>              .get(start..end)
> -            .and_then(Self::from_bytes_copy)
> +            .and_then(|b| Self::read_from_bytes(b).ok())
>              .ok_or(EINVAL)
>      }
>  }
>  
>  /// Header for code and data load offsets.
>  #[repr(C)]
> -#[derive(Debug, Clone)]
> +#[derive(Debug, Clone, FromBytes)]
>  struct HsLoadHeaderV2 {
>      // Offset at which the code starts.
>      os_code_offset: u32,
> @@ -191,9 +185,6 @@ struct HsLoadHeaderV2 {
>      num_apps: u32,
>  }
>  
> -// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
> -unsafe impl FromBytes for HsLoadHeaderV2 {}
> -
>  impl HsLoadHeaderV2 {
>      /// Returns the load header contained in `hs_fw`.
>      ///
> @@ -205,7 +196,7 @@ fn new(hs_fw: &HsFirmwareV2<'_>) -> Result<Self> {
>  
>  /// Header for app code loader.
>  #[repr(C)]
> -#[derive(Debug, Clone)]
> +#[derive(Debug, Clone, FromBytes)]
>  struct HsLoadHeaderV2App {
>      /// Offset at which to load the app code.
>      offset: u32,
> @@ -213,9 +204,6 @@ struct HsLoadHeaderV2App {
>      len: u32,
>  }
>  
> -// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
> -unsafe impl FromBytes for HsLoadHeaderV2App {}
> -
>  impl HsLoadHeaderV2App {
>      /// Returns the [`HsLoadHeaderV2App`] for app `idx` of `hs_fw`.
>      ///
> -- 
> 2.34.1
>