Re: [PATCH 2/7] drm/nova: use `zerocopy` in vbios.rs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] VBIOS byte stream reconstruction from MMIO uses `to_ne_bytes()` and struct parsing uses native integer types, corrupting VBIOS reading on big-endian architectures.
--

commit 1cc33aae3ba2ca65527c5d72b5ee976f3c73ac92
Author: Pedro Yudi Honda <niyudi.honda@usp.br>

drm/nova: use `zerocopy` in vbios.rs
    
This commit replaces the `transmute::FromBytes` trait with its `zerocopy`
equivalent for various VBIOS structures in vbios.rs. It also updates the
call sites accordingly to use the new trait methods.

> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
> index e6d144587c4ee..a3c0c06f6818d 100644
> --- a/drivers/gpu/nova-core/vbios.rs
> +++ b/drivers/gpu/nova-core/vbios.rs

[ ... ]

> @@ -359,7 +356,7 @@ pub(crate) fn fwsec_image(&self) -> &FwSecBiosImage {
>  }
>  
>  /// PCI Data Structure as defined in PCI Firmware Specification
> -#[derive(Debug, Clone)]
> +#[derive(Debug, Clone, FromBytes)]
>  #[repr(C)]
>  struct PcirStruct {
>      /// PCI Data Structure signature ("PCIR" or "NPDS")
>      signature: [u8; 4],
>      /// PCI Vendor ID (e.g., 0x10DE for NVIDIA)
>      vendor_id: u16,

[Severity: High]
This is a pre-existing issue, but since the VBIOS structures map directly to
little-endian VBIOS data, does using native integer types like u16 cause
the parsing to fail on big-endian architectures?

Also, since VbiosIterator::read_more() converts MMIO 32-bit words back into a
byte stream using word.to_ne_bytes():

    word.to_ne_bytes()
        .iter()
        .try_for_each(|&b| self.data.push(b, GFP_KERNEL))?;

doesn't this byte-swap the little-endian hardware register data on big-endian
systems?

Should explicit little-endian types (e.g.,
zerocopy::byteorder::little_endian::U16) and word.to_le_bytes() be used to
ensure the correct byte order is maintained?

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260625190553.7245-1-niyudi.honda@usp.br?part=2