[PATCH v2 1/3] rust: error: implement ZeroableOption for Error

[Alice Ryhl]

Rust Binder wants to store an Option<Error> in TransactionInfo, which
derives Zeroable. Implement ZeroableOption for Error so that
Option<Error> implements Zeroable.

Acked-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
---
 rust/kernel/error.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index e52793f77196..9003a1b86da8 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -199,8 +199,13 @@ macro_rules! declare_err {
 ///
 /// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`).
 #[derive(Clone, Copy, PartialEq, Eq)]
+#[repr(transparent)]
 pub struct Error(NonZeroI32);
 
+// SAFETY: `Error` is `repr(transparent)` over `NonZeroI32`, which is part of the option layout
+// optimization guarantee, so all zeroes is a valid representation for `None`.
+unsafe impl pin_init::ZeroableOption for Error {}
+
 impl Error {
     /// Creates an [`Error`] from a kernel error code.
     ///

-- 
2.56.0.385.gd3acb90ef8-goog