* [PATCH] rust: list: Add an example for `ListLinksSelfPtr` usage
2025-07-19 18:36 [PATCH] rust: list: undo unintended replacement of method name Miguel Ojeda
@ 2025-07-19 20:36 ` Boqun Feng
2025-07-19 20:54 ` Miguel Ojeda
2025-07-19 21:05 ` [PATCH] rust: list: undo unintended replacement of method name Tamir Duberstein
2025-07-19 22:16 ` Miguel Ojeda
2 siblings, 1 reply; 6+ messages in thread
From: Boqun Feng @ 2025-07-19 20:36 UTC (permalink / raw)
To: Miguel Ojeda
Cc: Alex Gaynor, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Andreas Hindborg, Alice Ryhl, Trevor Gross,
Danilo Krummrich, I Hsin Cheng, Albin Babu Varghese,
rust-for-linux, linux-kernel, patches
It appears that the support for `ListLinksSelfPtr` is dead code at the
moment [1]. Hence add an example similar to `ListLinks` usage to help
catching bugs and demonstrating the usage.
The example is mostly based on Alice's usage in binder driver[2].
Link: https://lore.kernel.org/rust-for-linux/20250719183649.596051-1-ojeda@kernel.org/ [1]
Link: https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-4-08ba9197f637@google.com/ [2]
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
rust/kernel/list.rs | 125 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 125 insertions(+)
diff --git a/rust/kernel/list.rs b/rust/kernel/list.rs
index 7ebb81b2a3d4..f66898738b31 100644
--- a/rust/kernel/list.rs
+++ b/rust/kernel/list.rs
@@ -38,6 +38,8 @@
///
/// # Examples
///
+/// Use [`ListLinks`] as the type of the intrusive field.
+///
/// ```
/// use kernel::list::*;
///
@@ -143,6 +145,129 @@
/// }
/// # Result::<(), Error>::Ok(())
/// ```
+///
+/// Use [`ListLinksSelfPtr`] as the type of the intrusive field. This allows a list of trait object
+/// type.
+///
+/// ```
+/// use kernel::list::*;
+///
+/// trait Trait {
+/// fn foo(&self) -> (&'static str, i32);
+/// }
+///
+/// #[pin_data]
+/// struct DTWrap<T: ?Sized> {
+/// #[pin]
+/// links: ListLinksSelfPtr<DTWrap<dyn Trait>>,
+/// value: T,
+/// }
+///
+/// impl<T> DTWrap<T> {
+/// fn new(value: T) -> Result<ListArc<Self>> {
+/// ListArc::pin_init(try_pin_init!(Self {
+/// value,
+/// links <- ListLinksSelfPtr::new(),
+/// }), GFP_KERNEL)
+/// }
+/// }
+///
+/// impl_has_list_links_self_ptr! {
+/// impl HasSelfPtr<DTWrap<dyn Trait>> for DTWrap<dyn Trait> { self.links }
+/// }
+/// impl_list_arc_safe! {
+/// impl{T: ?Sized} ListArcSafe<0> for DTWrap<T> { untracked; }
+/// }
+/// impl_list_item! {
+/// impl ListItem<0> for DTWrap<dyn Trait> { using ListLinksSelfPtr; }
+/// }
+///
+/// // Create a new empty list.
+/// let mut list = List::<DTWrap<dyn Trait>>::new();
+/// {
+/// assert!(list.is_empty());
+/// }
+///
+/// struct A(i32);
+///
+/// // `A` returns the inner value for `foo`.
+/// impl Trait for A { fn foo(&self) -> (&'static str, i32) { ("a", self.0) } }
+///
+/// struct B;
+/// // `B` always returns 42.
+/// impl Trait for B { fn foo(&self) -> (&'static str, i32) { ("b", 42) } }
+///
+/// // Insert 3 element using `push_back()`.
+/// list.push_back(DTWrap::new(A(15))?);
+/// list.push_back(DTWrap::new(A(32))?);
+/// list.push_back(DTWrap::new(B)?);
+///
+/// // Iterate over the list to verify the nodes were inserted correctly.
+/// // [A(15), A(32), B]
+/// {
+/// let mut iter = list.iter();
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("a", 15));
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("a", 32));
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("b", 42));
+/// assert!(iter.next().is_none());
+///
+/// // Verify the length of the list.
+/// assert_eq!(list.iter().count(), 3);
+/// }
+///
+/// // Pop the items from the list using `pop_back()` and verify the content.
+/// {
+/// assert_eq!(list.pop_back().ok_or(EINVAL)?.value.foo(), ("b", 42));
+/// assert_eq!(list.pop_back().ok_or(EINVAL)?.value.foo(), ("a", 32));
+/// assert_eq!(list.pop_back().ok_or(EINVAL)?.value.foo(), ("a", 15));
+/// }
+///
+/// // Insert 3 elements using `push_front()`.
+/// list.push_front(DTWrap::new(A(15))?);
+/// list.push_front(DTWrap::new(A(32))?);
+/// list.push_front(DTWrap::new(B)?);
+///
+/// // Iterate over the list to verify the nodes were inserted correctly.
+/// // [B, A(32), A(15)]
+/// {
+/// let mut iter = list.iter();
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("b", 42));
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("a", 32));
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("a", 15));
+/// assert!(iter.next().is_none());
+///
+/// // Verify the length of the list.
+/// assert_eq!(list.iter().count(), 3);
+/// }
+///
+/// // Pop the items from the list using `pop_front()` and verify the content.
+/// {
+/// assert_eq!(list.pop_back().ok_or(EINVAL)?.value.foo(), ("a", 15));
+/// assert_eq!(list.pop_back().ok_or(EINVAL)?.value.foo(), ("a", 32));
+/// }
+///
+/// // Push `list2` to `list` through `push_all_back()`.
+/// // list: [B]
+/// // list2: [B, A(25)]
+/// {
+/// let mut list2 = List::<DTWrap<dyn Trait>>::new();
+/// list2.push_back(DTWrap::new(B)?);
+/// list2.push_back(DTWrap::new(A(25))?);
+///
+/// list.push_all_back(&mut list2);
+///
+/// // list: [B, B, A(25)]
+/// // list2: []
+/// let mut iter = list.iter();
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("b", 42));
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("b", 42));
+/// assert_eq!(iter.next().ok_or(EINVAL)?.value.foo(), ("a", 25));
+/// assert!(iter.next().is_none());
+/// assert!(list2.is_empty());
+/// }
+/// # Result::<(), Error>::Ok(())
+/// ```
+///
pub struct List<T: ?Sized + ListItem<ID>, const ID: u64 = 0> {
first: *mut ListLinksFields,
_ty: PhantomData<ListArc<T, ID>>,
--
2.39.5 (Apple Git-154)
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] rust: list: undo unintended replacement of method name
2025-07-19 18:36 [PATCH] rust: list: undo unintended replacement of method name Miguel Ojeda
2025-07-19 20:36 ` [PATCH] rust: list: Add an example for `ListLinksSelfPtr` usage Boqun Feng
@ 2025-07-19 21:05 ` Tamir Duberstein
2025-07-19 22:16 ` Miguel Ojeda
2 siblings, 0 replies; 6+ messages in thread
From: Tamir Duberstein @ 2025-07-19 21:05 UTC (permalink / raw)
To: Miguel Ojeda
Cc: Alex Gaynor, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Andreas Hindborg, Alice Ryhl, Trevor Gross,
Danilo Krummrich, rust-for-linux, linux-kernel, patches
On Sat, Jul 19, 2025 at 2:37 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> When we renamed `Opaque::raw_get` to `cast_into`, there was one
> replacement that was not supposed to be there.
>
> It does not cause an issue so far because it is inside a macro rule (the
> `ListLinksSelfPtr` one) that is unused so far. However, it will start
> to be used soon.
>
> Thus fix it now.
>
> Fixes: 64fb810bce03 ("rust: types: rename Opaque::raw_get to cast_into")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Tamir Duberstein <tamird@gmail.com>
> ---
> rust/kernel/list/impl_list_item_mod.rs | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/rust/kernel/list/impl_list_item_mod.rs b/rust/kernel/list/impl_list_item_mod.rs
> index c1edba0a9501..3f6c30e14904 100644
> --- a/rust/kernel/list/impl_list_item_mod.rs
> +++ b/rust/kernel/list/impl_list_item_mod.rs
> @@ -252,7 +252,7 @@ unsafe fn view_value(links_field: *mut $crate::list::ListLinks<$num>) -> *const
> // the pointer stays in bounds of the allocation.
> let self_ptr = unsafe { (links_field as *const u8).add(spoff) }
> as *const ::core::cell::UnsafeCell<*const Self>;
> - let cell_inner = ::core::cell::UnsafeCell::cast_into(self_ptr);
> + let cell_inner = ::core::cell::UnsafeCell::raw_get(self_ptr);
> // SAFETY: This is not a data race, because the only function that writes to this
> // value is `prepare_to_insert`, but by the safety requirements the
> // `prepare_to_insert` method may not be called in parallel with `view_value` or
>
> base-commit: 23b128bba76776541dc09efaf3acf6242917e1f0
> --
> 2.50.1
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] rust: list: undo unintended replacement of method name
2025-07-19 18:36 [PATCH] rust: list: undo unintended replacement of method name Miguel Ojeda
2025-07-19 20:36 ` [PATCH] rust: list: Add an example for `ListLinksSelfPtr` usage Boqun Feng
2025-07-19 21:05 ` [PATCH] rust: list: undo unintended replacement of method name Tamir Duberstein
@ 2025-07-19 22:16 ` Miguel Ojeda
2 siblings, 0 replies; 6+ messages in thread
From: Miguel Ojeda @ 2025-07-19 22:16 UTC (permalink / raw)
To: Miguel Ojeda
Cc: Alex Gaynor, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Andreas Hindborg, Alice Ryhl, Trevor Gross,
Danilo Krummrich, rust-for-linux, linux-kernel, patches
On Sat, Jul 19, 2025 at 8:37 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> When we renamed `Opaque::raw_get` to `cast_into`, there was one
> replacement that was not supposed to be there.
>
> It does not cause an issue so far because it is inside a macro rule (the
> `ListLinksSelfPtr` one) that is unused so far. However, it will start
> to be used soon.
>
> Thus fix it now.
>
> Fixes: 64fb810bce03 ("rust: types: rename Opaque::raw_get to cast_into")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Applied to `rust-next` -- thanks everyone!
Cheers,
Miguel
^ permalink raw reply [flat|nested] 6+ messages in thread