linux-kernel - Re: [PATCH 1/4] rust: drm: gem: Use NonNull for Object::dev

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Message-Id: <6066097F-3A5C-4756-8772-300B27D2DF3A@collabora.com>
Date: Fri, 9 May 2025 17:59:15 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Lyude Paul <lyude@...hat.com>
Cc: dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>,
 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 <benno.lossin@...ton.me>,
 Andreas Hindborg <a.hindborg@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>,
 Asahi Lina <lina@...hilina.net>,
 Alyssa Rosenzweig <alyssa@...enzweig.io>
Subject: Re: [PATCH 1/4] rust: drm: gem: Use NonNull for Object::dev

Hi Lyude,

> On 1 May 2025, at 15:33, Lyude Paul <lyude@...hat.com> wrote:
> 
> There is usually not much of a reason to use a raw pointer in a data
> struct, so move this to NonNull instead.
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> ---
> rust/kernel/drm/gem/mod.rs | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
> index 0cafa4a424206..df8f9fdae5c22 100644
> --- a/rust/kernel/drm/gem/mod.rs
> +++ b/rust/kernel/drm/gem/mod.rs
> @@ -177,7 +177,7 @@ impl<T> BaseObject for T where Self: crate::types::AlwaysRefCounted + IntoGEMObj
> #[pin_data]
> pub struct Object<T: DriverObject + Send + Sync> {
>     obj: Opaque<bindings::drm_gem_object>,
> -    dev: *const drm::Device<T::Driver>,
> +    dev: NonNull<drm::Device<T::Driver>>,
>     #[pin]
>     data: T,
> }
> @@ -212,7 +212,7 @@ pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
>                 data <- T::new(dev, size),
>                 // INVARIANT: The drm subsystem guarantees that the `struct drm_device` will live
>                 // as long as the GEM object lives.
> -                dev,
> +                dev: dev.into(),
>             }),
>             GFP_KERNEL,
>         )?;
> @@ -237,7 +237,7 @@ pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
>     pub fn dev(&self) -> &drm::Device<T::Driver> {
>         // SAFETY: The DRM subsystem guarantees that the `struct drm_device` will live as long as
>         // the GEM object lives, hence the pointer must be valid.
> -        unsafe { &*self.dev }
> +        unsafe { self.dev.as_ref() }
>     }
> 
>     fn as_raw(&self) -> *mut bindings::drm_gem_object {
> -- 
> 2.48.1
> 
> 

Reviewed-by: Daniel Almeida <daniel.almeida@...labora.com>