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device: rust: improve safety comments

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Improve the wording of safety comments to be more explicit about what
exactly is guaranteed to be valid.

Suggested-by: Benno Lossin <benno.lossin@proton.me>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://lore.kernel.org/r/20240619133949.64638-1-dakr@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Danilo Krummrich 2024-06-19 15:39:17 +02:00 committed by Greg Kroah-Hartman
parent 892fb846d6
commit 4ead6c37b0
1 changed files with 6 additions and 3 deletions
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9
rust/kernel/device.rs
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@ -30,8 +30,10 @@ use core::ptr;
///
/// # Invariants
///
/// The pointer stored in `Self` is non-null and valid for the lifetime of the `ARef` instance. In
/// particular, the `ARef` instance owns an increment on the underlying object’s reference count.
/// A `Device` instance represents a valid `struct device` created by the C portion of the kernel.
///
/// Instances of this type are always reference-counted, that is, a call to `get_device` ensures
/// that the allocation remains valid at least until the matching call to `put_device`.
///
/// `bindings::device::release` is valid to be called from any thread, hence `ARef<Device>` can be
/// dropped from any thread.
@ -58,7 +60,8 @@ impl Device {
// CAST: `Self` is a `repr(transparent)` wrapper around `bindings::device`.
let ptr = ptr.cast::<Self>();
// SAFETY: By the safety requirements, ptr is valid.
// SAFETY: `ptr` is valid by the safety requirements of this function. By the above call to
// `bindings::get_device` we also own a reference to the underlying `struct device`.
unsafe { ARef::from_raw(ptr::NonNull::new_unchecked(ptr)) }
}