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authorWedson Almeida Filho <wedsonaf@gmail.com>2022-11-10 19:41:40 +0300
committerMiguel Ojeda <ojeda@kernel.org>2022-12-04 03:59:16 +0300
commitb9ecf9b9ac5969d7b7ea786ce5c76e24246df2c5 (patch)
tree745d370ce35c2004b4929733476add3f1a0a0850
parentba20915bae49024dab6ee582abdd4cd8944a3e55 (diff)
downloadlinux-b9ecf9b9ac5969d7b7ea786ce5c76e24246df2c5.tar.xz
rust: types: add `Opaque` type
Add the `Opaque` type, which is meant to be used with FFI objects that are never interpreted by Rust code, e.g.: struct Waiter { completion: Opaque<bindings::completion>, next: *mut Waiter, } It has the advantage that the objects don't have to be zero-initialised before calling their init functions, making the code performance closer to C. Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> [Reworded, adapted for upstream and applied latest changes] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
-rw-r--r--rust/kernel/types.rs25
1 files changed, 25 insertions, 0 deletions
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 3b0c44769708..e84e51ec9716 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -2,6 +2,31 @@
//! Kernel types.
+use core::{cell::UnsafeCell, mem::MaybeUninit};
+
+/// Stores an opaque value.
+///
+/// This is meant to be used with FFI objects that are never interpreted by Rust code.
+#[repr(transparent)]
+pub struct Opaque<T>(MaybeUninit<UnsafeCell<T>>);
+
+impl<T> Opaque<T> {
+ /// Creates a new opaque value.
+ pub const fn new(value: T) -> Self {
+ Self(MaybeUninit::new(UnsafeCell::new(value)))
+ }
+
+ /// Creates an uninitialised value.
+ pub const fn uninit() -> Self {
+ Self(MaybeUninit::uninit())
+ }
+
+ /// Returns a raw pointer to the opaque data.
+ pub fn get(&self) -> *mut T {
+ UnsafeCell::raw_get(self.0.as_ptr())
+ }
+}
+
/// A sum type that always holds either a value of type `L` or `R`.
pub enum Either<L, R> {
/// Constructs an instance of [`Either`] containing a value of type `L`.