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rust: drm: device: drop_in_place() the drm::Device in release()

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In drm::Device::new() we allocate with __drm_dev_alloc() and return an
ARef<drm::Device>.

When the reference count of the drm::Device falls to zero, the C code
automatically calls drm_dev_release(), which eventually frees the memory
allocated in drm::Device::new().

However, due to that, drm::Device::drop() is never called. As a result
the destructor of the user's private data, i.e. drm::Device::data is
never called. Hence, fix this by calling drop_in_place() from the DRM
device's release callback.

Fixes: 1e4b8896c0 ("rust: drm: add device abstraction")
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20250629153747.72536-1-dakr@kernel.org
This commit is contained in:
Danilo Krummrich 2025-06-29 17:37:42 +02:00
parent e79d0ba605
commit 2e9fdbe5ec
1 changed files with 11 additions and 1 deletions
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12
rust/kernel/drm/device.rs
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@ -66,7 +66,7 @@ impl<T: drm::Driver> Device<T> {
open: Some(drm::File::<T::File>::open_callback),
postclose: Some(drm::File::<T::File>::postclose_callback),
unload: None,
release: None,
release: Some(Self::release),
master_set: None,
master_drop: None,
debugfs_init: None,
@ -162,6 +162,16 @@ pub unsafe fn as_ref<'a>(ptr: *const bindings::drm_device) -> &'a Self {
// SAFETY: `ptr` is valid by the safety requirements of this function.
unsafe { &*ptr.cast() }
}
extern "C" fn release(ptr: *mut bindings::drm_device) {
// SAFETY: `ptr` is a valid pointer to a `struct drm_device` and embedded in `Self`.
let this = unsafe { Self::from_drm_device(ptr) };
// SAFETY:
// - When `release` runs it is guaranteed that there is no further access to `this`.
// - `this` is valid for dropping.
unsafe { core::ptr::drop_in_place(this) };
}
}
impl<T: drm::Driver> Deref for Device<T> {