[PATCH v4 4/7] rust: page: define trait AsPageIter

[Danilo Krummrich <dakr@kernel.org>]

The AsPageIter trait provides a common interface for types that
provide a page iterator, such as VmallocPageIter.

Subsequent patches will leverage this to let VBox and VVec provide a
VmallocPageIter though this trait.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/page.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 631718a6ad7d..8c5022c20472 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -103,6 +103,18 @@ fn deref(&self) -> &Self::Target {
     }
 }
 
+/// Trait to be implemented by types, which provide an [`Iterator`] implementation of
+/// [`BorrowedPage`] items, such as [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
+pub trait AsPageIter {
+    /// The [`Iterator`] type, e.g. [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
+    type Iter<'a>: Iterator<Item = BorrowedPage<'a>>
+    where
+        Self: 'a;
+
+    /// Returns an [`Iterator`] of [`BorrowedPage`] items over all pages owned by `self`.
+    fn page_iter(&mut self) -> Self::Iter<'_>;
+}
+
 /// A pointer to a page that owns the page allocation.
 ///
 /// # Invariants
-- 
2.50.1