uefi: Change Pointer::wait_for_input_event to return an option

Our `Event` type always represents a non-null pointer, but the spec doesn't guarantee that the `wait_for_input` event will be non-null.

Author: nicholasbishop

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Changed
 - `Input::wait_for_key_event` now returns an `Option<Event>`, and is no longer `const`.
+- `Protocol::wait_for_input_event` now returns an `Option<Event>`.
 - `LoadedImage::device` now returns an `Option<Handle>` and is no longer `const`.
 - `BootServices::get_image_file_system` now returns
  `ScopedProtocol<SimpleFileSystem>` instead of `fs::FileSystem`.

uefi/src/proto/console/pointer/mod.rs

@@ -9,7 +9,7 @@ use crate::{Event, Result, Status, StatusExt};
 pub struct Pointer {
  reset: unsafe extern "efiapi" fn(this: &mut Pointer, ext_verif: bool) -> Status,
  get_state: unsafe extern "efiapi" fn(this: &Pointer, state: *mut PointerState) -> Status,
- wait_for_input: Event,
+ wait_for_input: Option<Event>,
  mode: *const PointerMode,
 }
 
@@ -46,7 +46,7 @@ impl Pointer {
  /// Event to be used with `BootServices::wait_for_event()` in order to wait
  /// for input from the pointer device
  #[must_use]
- pub const fn wait_for_input_event(&self) -> &Event {
+ pub const fn wait_for_input_event(&self) -> &Option<Event> {
  &self.wait_for_input
  }