Re: [PATCH] Partially revert "rust: drm: gem: Implement AlwaysRefCounted for all gem objects automatically"

["Danilo Krummrich" <dakr@kernel.org>]

On Thu Jul 24, 2025 at 9:15 PM CEST, Lyude Paul wrote:
> -// SAFETY: All gem objects are refcounted.
> -unsafe impl<T: IntoGEMObject> AlwaysRefCounted for T {
> -    fn inc_ref(&self) {
> -        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
> -        unsafe { bindings::drm_gem_object_get(self.as_raw()) };
> -    }
> -
> -    unsafe fn dec_ref(obj: NonNull<Self>) {
> -        // SAFETY: We either hold the only refcount on `obj`, or one of many - meaning that no one
> -        // else could possibly hold a mutable reference to `obj` and thus this immutable reference
> -        // is safe.
> -        let obj = unsafe { obj.as_ref() }.as_raw();
> -
> -        // SAFETY:
> -        // - The safety requirements guarantee that the refcount is non-zero.
> -        // - We hold no references to `obj` now, making it safe for us to potentially deallocate it.
> -        unsafe { bindings::drm_gem_object_put(obj) };
> -    }
> -}

IIUC, you'll add rust/kernel/drm/gem/shmem.rs with a new type shmem::Object that
implements IntoGEMObject, right?

If this is correct, I think that should work.

Do I miss anything?