Re: [PATCH v2 1/5] drm/nova: use `zerocopy` in firmware.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.rs, replace the following `transmute` traits with their
> `zerocopy` equivalents:
> 
> - `transmute::FromBytes` -> `zerocopy::FromBytes`
> 
> Update call sites accordingly.
> 
> Note that the module `elf` is untouched, as the bindings generated by
> bindgen do not implement `FromBytes` for the structs.

Also I believe this module is pretty temporary and going to go away.

Everything here is pretty mechanical though, and looks good to me so:

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

> Signed-off-by: Pedro Yudi Honda <niyudi.honda@usp.br>
> ---
>  drivers/gpu/nova-core/firmware.rs                  | 10 +++-------
>  drivers/gpu/nova-core/firmware/fwsec/bootloader.rs |  4 +++-
>  2 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
> index a94820a3b335..80ce0df244a8 100644
> --- a/drivers/gpu/nova-core/firmware.rs
> +++ b/drivers/gpu/nova-core/firmware.rs
> @@ -11,8 +11,7 @@
>      device,
>      firmware,
>      prelude::*,
> -    str::CString,
> -    transmute::FromBytes, //
> +    str::CString, //
>  };
>  
>  use crate::{
> @@ -347,7 +346,7 @@ fn no_patch_signature(self) -> FirmwareObject<F, Signed> {
>  
>  /// Header common to most firmware files.
>  #[repr(C)]
> -#[derive(Debug, Clone)]
> +#[derive(Debug, Clone, FromBytes)]
>  struct BinHdr {
>      /// Magic number, must be `0x10de`.
>      bin_magic: u32,
> @@ -363,9 +362,6 @@ struct BinHdr {
>      data_size: u32,
>  }
>  
> -// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
> -unsafe impl FromBytes for BinHdr {}
> -
>  // A firmware blob starting with a `BinHdr`.
>  struct BinFirmware<'a> {
>      hdr: BinHdr,
> @@ -381,7 +377,7 @@ fn new(fw: &'a firmware::Firmware) -> Result<Self> {
>  
>          fw.get(0..size_of::<BinHdr>())
>              // Extract header.
> -            .and_then(BinHdr::from_bytes_copy)
> +            .and_then(|b| BinHdr::read_from_bytes(b).ok())
>              // Validate header.
>              .filter(|hdr| hdr.bin_magic == BIN_MAGIC)
>              .map(|hdr| Self { hdr, fw })
> diff --git a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> index d9fafd2eea5b..66b9f4d1b41c 100644
> --- a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> +++ b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> @@ -25,6 +25,8 @@
>      },
>  };
>  
> +use zerocopy::FromBytes as _;
> +
>  use crate::{
>      driver::Bar0,
>      falcon::{
> @@ -150,7 +152,7 @@ pub(crate) fn new(
>          let hdr = fw
>              .data()
>              .get(0..size_of::<BinHdr>())
> -            .and_then(BinHdr::from_bytes_copy)
> +            .and_then(|b| BinHdr::read_from_bytes(b).ok())
>              .ok_or(EINVAL)?;
>  
>          let desc = {
> -- 
> 2.34.1
>