linux-kernel - Re: [PATCH 3/4] rust: drm: gem: s/into_gem_obj()/as_gem

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Message-Id: <128B16D7-2E18-440E-A2EE-C7194194D7D3@collabora.com>
Date: Fri, 9 May 2025 18:42:12 -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,
 David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>,
 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>,
 Alyssa Rosenzweig <alyssa@...enzweig.io>,
 Asahi Lina <lina@...hilina.net>
Subject: Re: [PATCH 3/4] rust: drm: gem: s/into_gem_obj()/as_gem_obj()/

Hi Lyude,

> On 1 May 2025, at 15:33, Lyude Paul <lyude@...hat.com> wrote:
> 
> There's a few changes here:
> * The rename, of course (this should also let us drop the clippy annotation
>  here)
> * Return *mut bindings::drm_gem_object instead of
>  &Opaque<bindings::drm_gem_object> - the latter doesn't really have any
>  benefit and just results in conversion from the rust type to the C type
>  having to be more verbose than necessary.
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> ---
> rust/kernel/drm/gem/mod.rs | 21 +++++++--------------
> 1 file changed, 7 insertions(+), 14 deletions(-)
> 
> diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
> index f70531889c21f..55b2f1d056c39 100644
> --- a/rust/kernel/drm/gem/mod.rs
> +++ b/rust/kernel/drm/gem/mod.rs
> @@ -42,8 +42,7 @@ pub trait IntoGEMObject: Sized + super::private::Sealed {
> 
>     /// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as
>     /// this owning object is valid.
> -    #[allow(clippy::wrong_self_convention)]
> -    fn into_gem_obj(&self) -> &Opaque<bindings::drm_gem_object>;
> +    fn as_gem_obj(&self) -> *mut bindings::drm_gem_object;
> 
>     /// Converts a pointer to a `struct drm_gem_object` into a reference to `Self`.
>     ///
> @@ -99,8 +98,8 @@ extern "C" fn close_callback<T: BaseDriverObject<U>, U: BaseObject>(
> impl<T: DriverObject> IntoGEMObject for Object<T> {
>     type Driver = T::Driver;
> 
> -    fn into_gem_obj(&self) -> &Opaque<bindings::drm_gem_object> {
> -        &self.obj
> +    fn as_gem_obj(&self) -> *mut bindings::drm_gem_object {
> +        self.obj.get()
>     }
> 
>     unsafe fn as_ref<'a>(self_ptr: *mut bindings::drm_gem_object) -> &'a Self {
> @@ -119,7 +118,7 @@ pub trait BaseObject
>     fn size(&self) -> usize {
>         // SAFETY: `self.into_gem_obj()` is guaranteed to be a pointer to a valid `struct
>         // drm_gem_object`.
> -        unsafe { (*self.into_gem_obj().get()).size }
> +        unsafe { (*self.as_gem_obj()).size }
>     }
> 
>     /// Creates a new handle for the object associated with a given `File`
> @@ -131,11 +130,7 @@ fn create_handle(
>         let mut handle: u32 = 0;
>         // SAFETY: The arguments are all valid per the type invariants.
>         to_result(unsafe {
> -            bindings::drm_gem_handle_create(
> -                file.as_raw().cast(),
> -                self.into_gem_obj().get(),
> -                &mut handle,
> -            )
> +            bindings::drm_gem_handle_create(file.as_raw().cast(), self.as_gem_obj(), &mut handle)
>         })?;
>         Ok(handle)
>     }
> @@ -171,13 +166,11 @@ fn lookup_handle(
>     /// Creates an mmap offset to map the object from userspace.
>     fn create_mmap_offset(&self) -> Result<u64> {
>         // SAFETY: The arguments are valid per the type invariant.
> -        to_result(unsafe { bindings::drm_gem_create_mmap_offset(self.into_gem_obj().get()) })?;
> +        to_result(unsafe { bindings::drm_gem_create_mmap_offset(self.as_gem_obj()) })?;
> 
>         // SAFETY: The arguments are valid per the type invariant.
>         Ok(unsafe {
> -            bindings::drm_vma_node_offset_addr(ptr::addr_of_mut!(
> -                (*self.into_gem_obj().get()).vma_node
> -            ))
> +            bindings::drm_vma_node_offset_addr(ptr::addr_of_mut!((*self.as_gem_obj()).vma_node))

Hmm, I thought we were on a quest to remove addr_of_mut!() in favor of &raw mut?

Anyways, this is again orthogonal to your patch.

>         })
>     }
> }
> -- 
> 2.48.1
> 
> 

This looks good.

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