linux-kernel - Re: [PATCH v2 3/7] gpu: nova-core: vbios: add conversion to u8 for BiosImageType

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Message-ID: <20251027173756.GA3188703@joelbox2>
Date: Mon, 27 Oct 2025 13:37:56 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: Alexandre Courbot <acourbot@...dia.com>
Cc: 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>,
	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 3/7] gpu: nova-core: vbios: add conversion to u8 for
 BiosImageType

Hello Alex,

On Mon, Oct 27, 2025 at 09:54:43PM +0900, Alexandre Courbot wrote:
> Since `BiosImageType` is `repr(u8)`, if can safely be converted into a
> `u8` but this is not obvious when doing this in the code.
> 
> Instead, implement `From<BiosImageType>` for `u8` so the cast can be
> done in a single place, with a justifying comment.
> 
> Acked-by: Danilo Krummrich <dakr@...nel.org>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
>  drivers/gpu/nova-core/vbios.rs | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
> index dbe0d6e4a015..a521c0a4df0f 100644
> --- a/drivers/gpu/nova-core/vbios.rs
> +++ b/drivers/gpu/nova-core/vbios.rs
> @@ -50,6 +50,13 @@ fn try_from(code: u8) -> Result<Self> {
>      }
>  }
>  
> +impl From<BiosImageType> for u8 {
> +    fn from(value: BiosImageType) -> Self {
> +        // `BiosImageType` is `repr(u8)` and thus convertible without loss.
> +        value as u8
> +    }
> +}
> +
>  // PMU lookup table entry types. Used to locate PMU table entries
>  // in the Fwsec image, corresponding to falcon ucodes.
>  #[expect(dead_code)]
> @@ -711,7 +718,7 @@ fn image_type(&self) -> Result<BiosImageType> {
>      fn is_last(&self) -> bool {
>          // For NBSI images (type == 0x70), return true as they're
>          // considered the last image
> -        if self.pcir.code_type == BiosImageType::Nbsi as u8 {
> +        if self.pcir.code_type == BiosImageType::Nbsi.into() {

I strongly prefer u8::from(BiosImageType::Nbsi) here so there is no loss of
readability of the type. Can we please use ::from()?

thanks,

 - Joel


>              return true;
>          }
>  
> 
> -- 
> 2.51.0
>