linux-kernel - [PATCH v3 5/6] rust: list: add `impl_list

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Message-Id: <20250423-list-no-offset-v3-5-9d0c2b89340e@gmail.com>
Date: Wed, 23 Apr 2025 12:30:06 -0400
From: Tamir Duberstein <tamird@...il.com>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
 Benno Lossin <benno.lossin@...ton.me>, 
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
 Bjorn Helgaas <bhelgaas@...gle.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-pci@...r.kernel.org, Tamir Duberstein <tamird@...il.com>
Subject: [PATCH v3 5/6] rust: list: add `impl_list_item!` examples

There's a comprehensive example in `rust/kernel/list.rs` but it doesn't
exercise the `using ListLinksSelfPtr` variant nor the generic cases. Add
that here. Generalize `impl_has_list_links_self_ptr` to handle nested
fields in the same manner as `impl_has_list_links`.

Signed-off-by: Tamir Duberstein <tamird@...il.com>
---
 rust/kernel/list/impl_list_item_mod.rs | 96 ++++++++++++++++++++++++++++++++--
 1 file changed, 93 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/list/impl_list_item_mod.rs b/rust/kernel/list/impl_list_item_mod.rs
index 3f6cd1b090a7..df21070e1cf6 100644
--- a/rust/kernel/list/impl_list_item_mod.rs
+++ b/rust/kernel/list/impl_list_item_mod.rs
@@ -82,20 +82,20 @@ macro_rules! impl_has_list_links_self_ptr {
     ($(impl$({$($generics:tt)*})?
        HasSelfPtr<$item_type:ty $(, $id:tt)?>
        for $self:ty
-       { self.$field:ident }
+       { self$(.$field:ident)* }
     )*) => {$(
         // SAFETY: The implementation of `raw_get_list_links` only compiles if the field has the
         // right type.
         unsafe impl$(<$($generics)*>)? $crate::list::HasSelfPtr<$item_type $(, $id)?> for $self {}
 
         unsafe impl$(<$($generics)*>)? $crate::list::HasListLinks$(<$id>)? for $self {
-            const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize;
+            const OFFSET: usize = ::core::mem::offset_of!(Self, $($field).*) as usize;
 
             #[inline]
             unsafe fn raw_get_list_links(ptr: *mut Self) -> *mut $crate::list::ListLinks$(<$id>)? {
                 // SAFETY: The caller promises that the pointer is not dangling.
                 let ptr: *mut $crate::list::ListLinksSelfPtr<$item_type $(, $id)?> =
-                    unsafe { ::core::ptr::addr_of_mut!((*ptr).$field) };
+                    unsafe { ::core::ptr::addr_of_mut!((*ptr)$(.$field)*) };
                 ptr.cast()
             }
         }
@@ -109,6 +109,96 @@ unsafe fn raw_get_list_links(ptr: *mut Self) -> *mut $crate::list::ListLinks$(<$
 /// implement that trait.
 ///
 /// [`ListItem`]: crate::list::ListItem
+///
+/// # Examples
+///
+/// ```
+/// #[pin_data]
+/// struct SimpleListItem {
+///     value: u32,
+///     #[pin]
+///     links: kernel::list::ListLinks,
+/// }
+///
+/// kernel::list::impl_has_list_links! {
+///     impl HasListLinks<0> for SimpleListItem { self.links }
+/// }
+///
+/// kernel::list::impl_list_arc_safe! {
+///     impl ListArcSafe<0> for SimpleListItem { untracked; }
+/// }
+///
+/// kernel::list::impl_list_item! {
+///     impl ListItem<0> for SimpleListItem { using ListLinks; }
+/// }
+///
+/// struct ListLinksHolder {
+///     inner: kernel::list::ListLinks,
+/// }
+///
+/// #[pin_data]
+/// struct ComplexListItem<T, U> {
+///     value: Result<T, U>,
+///     #[pin]
+///     links: ListLinksHolder,
+/// }
+///
+/// kernel::list::impl_has_list_links! {
+///     impl{T, U} HasListLinks<0> for ComplexListItem<T, U> { self.links.inner }
+/// }
+///
+/// kernel::list::impl_list_arc_safe! {
+///     impl{T, U} ListArcSafe<0> for ComplexListItem<T, U> { untracked; }
+/// }
+///
+/// kernel::list::impl_list_item! {
+///     impl{T, U} ListItem<0> for ComplexListItem<T, U> { using ListLinks; }
+/// }
+/// ```
+///
+/// ```
+/// #[pin_data]
+/// struct SimpleListItem {
+///     value: u32,
+///     #[pin]
+///     links: kernel::list::ListLinksSelfPtr<SimpleListItem>,
+/// }
+///
+/// kernel::list::impl_list_arc_safe! {
+///     impl ListArcSafe<0> for SimpleListItem { untracked; }
+/// }
+///
+/// kernel::list::impl_has_list_links_self_ptr! {
+///     impl HasSelfPtr<SimpleListItem> for SimpleListItem { self.links }
+/// }
+///
+/// kernel::list::impl_list_item! {
+///     impl ListItem<0> for SimpleListItem { using ListLinksSelfPtr; }
+/// }
+///
+/// struct ListLinksSelfPtrHolder<T, U> {
+///     inner: kernel::list::ListLinksSelfPtr<ComplexListItem<T, U>>,
+/// }
+///
+/// #[pin_data]
+/// struct ComplexListItem<T, U> {
+///     value: Result<T, U>,
+///     #[pin]
+///     links: ListLinksSelfPtrHolder<T, U>,
+/// }
+///
+/// kernel::list::impl_list_arc_safe! {
+///     impl{T, U} ListArcSafe<0> for ComplexListItem<T, U> { untracked; }
+/// }
+///
+/// kernel::list::impl_has_list_links_self_ptr! {
+///     impl{T, U} HasSelfPtr<ComplexListItem<T, U>> for ComplexListItem<T, U> { self.links.inner }
+/// }
+///
+/// kernel::list::impl_list_item! {
+///     impl{T, U} ListItem<0> for ComplexListItem<T, U> { using ListLinksSelfPtr; }
+/// }
+/// ```
 #[macro_export]
 macro_rules! impl_list_item {
     (

-- 
2.49.0