rust: types: Make Opaque::get const

[PATCH] rust: types: Make Opaque::get const

Posted by Boqun Feng 1 year, 10 months ago

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@gmail.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

Re: [PATCH] rust: types: Make Opaque::get const

Posted by Miguel Ojeda 1 year, 9 months ago

On Mon, Apr 1, 2024 at 11:46 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> 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@gmail.com>

Applied to `rust-next` -- thanks everyone!

Cheers,
Miguel

Re: [PATCH] rust: types: Make Opaque::get const

Posted by Benno Lossin 1 year, 10 months ago

On 01.04.24 23:45, Boqun Feng wrote:
> 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@gmail.com>
> ---
>   rust/kernel/types.rs | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Benno Lossin <benno.lossin@proton.me>

-- 
Cheers,
Benno

Re: [PATCH] rust: types: Make Opaque::get const

Posted by Alice Ryhl 1 year, 10 months ago

On Mon, Apr 1, 2024 at 11:46 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> 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@gmail.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH] rust: types: Make Opaque::get const

Posted by Wedson Almeida Filho 1 year, 10 months ago

On Mon, 1 Apr 2024 at 18:46, Boqun Feng <boqun.feng@gmail.com> wrote:
>
> 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@gmail.com>

Reviewed-by: Wedson Almeida Filho <walmeida@microsoft.com>