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    Subject[PATCH 4/5] rust: types: implement `ForeignOwnable` for the unit type
    Date
    This allows us to use the unit type `()` when we have no object whose
    ownership must be managed but one implementing the `ForeignOwnable`
    trait is needed.

    Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
    ---
    rust/kernel/types.rs | 13 +++++++++++++
    1 file changed, 13 insertions(+)

    diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
    index e037c262f23e..8f80cffbff59 100644
    --- a/rust/kernel/types.rs
    +++ b/rust/kernel/types.rs
    @@ -85,6 +85,19 @@ impl<T: 'static> ForeignOwnable for Box<T> {
    }
    }

    +impl ForeignOwnable for () {
    + type Borrowed<'a> = ();
    +
    + fn into_foreign(self) -> *const core::ffi::c_void {
    + // We use 1 to be different from a null pointer.
    + 1usize as _
    + }
    +
    + unsafe fn borrow<'a>(_: *const core::ffi::c_void) -> Self::Borrowed<'a> {}
    +
    + unsafe fn from_foreign(_: *const core::ffi::c_void) -> Self {}
    +}
    +
    /// Runs a cleanup function/closure when dropped.
    ///
    /// The [`ScopeGuard::dismiss`] function prevents the cleanup function from running.
    --
    2.34.1
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