Re: [PATCH] rust/drm/gem: initialize callbacks with ..pin_init::zeroed()

[Klara Modin]

On 2026-09-08 21:09:40 +0200, Klara Modin wrote:
> On 2026-09-08 20:57:05 +0200, Klara Modin wrote:
> > On 2026-09-08 18:05:54 +0000, sashiko-bot@xxxxxxxxxx wrote:
> > > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> > > - [Medium] Incomplete fix: missing `handle_free` field in conditionally compiled `shmem.rs`.
> > > --
> > > 
> > > commit b5b83bb373847c99ca6d286c268d2e0ffab299f0
> > > Author: Klara Modin <klarasmodin@xxxxxxxxx>
> > > 
> > > rust/drm/gem: initialize callbacks with ..pin_init::zeroed()
> > > 
> > > This commit updates the drm_gem_object_funcs struct initialization in the DRM
> > > GEM module to use pin_init::zeroed() instead of explicitly assigning None to
> > > unused callbacks. This fixes a build failure caused by a newly added callback
> > > field in the C structure.
> > > 
> > > Closes: https://lore.kernel.org/all/aaef18cd-ab55-4fb8-8563-ca3a5ea9cbc6@xxxxxxxxxxxxx
> > > 
> > > > diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
> > > > index e1ebad77ebe2a..c63b0fe5a15e1 100644
> > > > --- a/rust/kernel/drm/gem/mod.rs
> > > > +++ b/rust/kernel/drm/gem/mod.rs
> > > > @@ -266,18 +266,8 @@ impl<T: DriverObject, Ctx: DeviceContext> Object<T, Ctx> {
> > > >          free: Some(Self::free_callback),
> > > >          open: Some(open_callback::<T>),
> > > >          close: Some(close_callback::<T>),
> > > > -        print_info: None,
> > > > -        export: None,
> > > > -        pin: None,
> > > > -        unpin: None,
> > > > -        get_sg_table: None,
> > > > -        vmap: None,
> > > > -        vunmap: None,
> > > > -        mmap: None,
> > > > -        status: None,
> > > >          vm_ops: core::ptr::null_mut(),
> > > > -        evict: None,
> > > > -        rss: None,
> > > > +        ..pin_init::zeroed()
> > > >      };
> > > 
> > > [Severity: Medium]-
> > > Does this commit miss a similar update in rust/kernel/drm/gem/shmem.rs?
> > > 
> > > The VTABLE initialization in shmem.rs explicitly lists fields without
> > > using pin_init::zeroed(), similar to what was fixed here. When compiling
> > > with CONFIG_RUST_DRM_GEM_SHMEM_HELPER=y, won't this cause a missing
> > > field error for the newly added handle_free callback?
> > 
> > Sure, but it should probably be a different patch in that case. The
> > current patch fixes an issue to a currently existing build failure,
> > while the issue mentioned here has not manifested yet.
> 
> On second thought, this is seems to be using the same binding so this
> might be accurate.

Confirmed, on an arm64 build with the Tyr driver enabled:

 error[E0063]: missing field `handle_free` in initializer of `drm_gem_object_funcs`
    --> /home/klara/git/linux/trees/next-local/rust/kernel/drm/gem/shmem.rs:130:52
     |
 130 |     const VTABLE: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs {
     |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `handle_free`
 
 error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0063`.

I'll wait a while for other thoughts and otherwise respin with this
included.

> 
> > 
> > Regards,
> > Klara Modin
> > 
> > > 
> > > rust/kernel/drm/gem/shmem.rs:
> > >     const VTABLE: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs {
> > >         free: Some(Self::free_callback),
> > >         open: Some(super::open_callback::<T>),
> > >         close: Some(super::close_callback::<T>),
> > >         print_info: Some(bindings::drm_gem_shmem_object_print_info),
> > >         export: None,
> > >         pin: Some(bindings::drm_gem_shmem_object_pin),
> > >         unpin: Some(bindings::drm_gem_shmem_object_unpin),
> > >         get_sg_table: Some(bindings::drm_gem_shmem_object_get_sg_table),
> > >         vmap: Some(bindings::drm_gem_shmem_object_vmap),
> > >         vunmap: Some(bindings::drm_gem_shmem_object_vunmap),
> > >         mmap: Some(bindings::drm_gem_shmem_object_mmap),
> > >         status: None,
> > >         rss: None,
> > >         #[allow(unused_unsafe, reason = "Safe since Rust 1.82.0")]
> > >         // SAFETY: drm_gem_shmem_vm_ops is a valid, static const on the C side.
> > >         vm_ops: unsafe { &raw const bindings::drm_gem_shmem_vm_ops },
> > >         evict: None,
> > >     };
> > > 
> > > -- 
> > > Sashiko AI review · https://sashiko.dev/#/patchset/20260908175427.47207-1-klarasmodin@xxxxxxxxx?part=1