From 8802e168437840ea0b1d5ca571cd3e95681e9e2b Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Tue, 24 Jun 2025 15:27:55 +0000 Subject: rust: types: add Opaque::cast_from Since commit b20fbbc08a36 ("rust: check type of `$ptr` in `container_of!`") we have enforced that the field pointer passed to container_of! must match the declared field. This caused mismatches when using a pointer to bindings::x for fields of type Opaque. This situation encourages the user to simply pass field.cast() to the container_of! macro, but this is not great because you might accidentally pass a *mut bindings::y when the field type is Opaque, which would be wrong. To help catch this kind of mistake, add a new Opaque::cast_from that wraps a raw pointer in Opaque without changing the inner type. Also update the docs to reflect this as well as some existing users. Signed-off-by: Alice Ryhl Acked-by: Andreas Hindborg Acked-by: Boqun Feng Reviewed-by: Danilo Krummrich Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20250624-opaque-from-raw-v2-1-e4da40bdc59c@google.com Signed-off-by: Miguel Ojeda --- rust/kernel/types.rs | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'rust/kernel/types.rs') diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index 63a2559a545f..9de8e0011b1d 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -413,6 +413,11 @@ impl Opaque { pub const fn raw_get(this: *const Self) -> *mut T { UnsafeCell::raw_get(this.cast::>>()).cast::() } + + /// The opposite operation of [`Opaque::raw_get`]. + pub const fn cast_from(this: *const T) -> *const Self { + this.cast() + } } /// Types that are _always_ reference counted. -- cgit v1.2.3