linux-kernel - Re: [PATCH v2 2/7] gpu: nova-core: vbios: remove unneeded u8 conversions

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Message-ID: <50f8b846-aead-43d3-b3f0-49e67b1952b5@nvidia.com>
Date: Mon, 27 Oct 2025 13:41:47 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: Alexandre Courbot <acourbot@...dia.com>, Alice Ryhl
 <aliceryhl@...gle.com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
 Gary Guo <gary@...yguo.net>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>,
 Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>
Cc: John Hubbard <jhubbard@...dia.com>, Alistair Popple <apopple@...dia.com>,
 Timur Tabi <ttabi@...dia.com>, Edwin Peer <epeer@...dia.com>,
 nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
 Danilo Krummrich <dakr@...nel.org>
Subject: Re: [PATCH v2 2/7] gpu: nova-core: vbios: remove unneeded u8
 conversions

Hello Alex,

On 10/27/2025 8:54 AM, Alexandre Courbot wrote:
> These variables were read from the u8 array `data` and converted to a
> `usize`, before being converted back to a `u8`. Just re-read them from
> the source to avoid using `as`.
> 
> Acked-by: Danilo Krummrich <dakr@...nel.org>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
>  drivers/gpu/nova-core/vbios.rs | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
> index 943b0dac31df..dbe0d6e4a015 100644
> --- a/drivers/gpu/nova-core/vbios.rs
> +++ b/drivers/gpu/nova-core/vbios.rs
> @@ -911,9 +911,9 @@ fn new(dev: &device::Device, data: &[u8]) -> Result<Self> {
>  
>          Ok(PmuLookupTable {
>              version: data[0],
> -            header_len: header_len as u8,
> -            entry_len: entry_len as u8,
> -            entry_count: entry_count as u8,
> +            header_len: data[1],
> +            entry_len: data[2],
> +            entry_count: data[3],
>              table_data,

Why not just change PmuLookupTable to:

struct PmuLookupTable {
    version: u8,
    header_len: usize,
    entry_len: usize,
    entry_count: usize,
    table_data: KVec<u8>,
}

That is cleaner and removes the issue while allowing to use the local variables
(and also makes sense to be usize as these 3 fields are size-like fields).

thanks,

 - Joel