linux-kernel - [PATCH] rust: types: Make Opaque::get const

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Date: Mon,  1 Apr 2024 14:45:36 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Boqun Feng <boqun.feng@...il.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...sung.com>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Martin Rodriguez Reboredo <yakoyoku@...il.com>,
	Obei Sideg <linux@...i.io>
Subject: [PATCH] rust: types: Make Opaque::get const

To support a potential usage:

    static foo: Opaque<Foo> = ..; // Or defined in an extern block.

    ...

    fn bar() {
        let ptr = foo.get();
    }

`Opaque::get` need to be `const`, otherwise compiler will complain
because calls on statics are limited to const functions.

Also `Opaque::get` should be naturally `const` since it's a composition
of two `const` functions: `UnsafeCell::get` and `ptr::cast`.

Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 rust/kernel/types.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 0949f9971074..25953c8f8acf 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -315,7 +315,7 @@ pub fn ffi_init(init_func: impl FnOnce(*mut T)) -> impl PinInit<Self> {
     }
 
     /// Returns a raw pointer to the opaque data.
-    pub fn get(&self) -> *mut T {
+    pub const fn get(&self) -> *mut T {
         UnsafeCell::get(&self.value).cast::<T>()
     }
 
-- 
2.44.0