linux.git/rust/kernel/list/impl_list_item_mod.rs, branch v6.13 Linux kernel source tree rust: list: support heterogeneous lists 2024-08-23T04:26:57+00:00 Alice Ryhl aliceryhl@google.com 2024-08-14T08:05:28+00:00 2003c04b059759b0ec3bff108f24ded9de86a726 Support linked lists that can hold many different structs at once. This is generally done using trait objects. The main challenge is figuring what the struct is given only a pointer to the ListLinks. We do this by storing a pointer to the struct next to the ListLinks field. The container_of operation will then just read that pointer. When the type is a trait object, that pointer will be a fat pointer whose metadata is a vtable that tells you what kind of struct it is. Heterogeneous lists are heavily used by Rust Binder. There are a lot of so-called todo lists containing various events that need to be delivered to userspace next time userspace calls into the driver. And there are quite a few different todo item types: incoming transaction, changes to refcounts, death notifications, and more. Reviewed-by: Benno Lossin <benno.lossin@proton.me> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240814-linked-list-v5-9-f5f5e8075da0@google.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org> 
Support linked lists that can hold many different structs at once. This
is generally done using trait objects. The main challenge is figuring
what the struct is given only a pointer to the ListLinks.

We do this by storing a pointer to the struct next to the ListLinks
field. The container_of operation will then just read that pointer. When
the type is a trait object, that pointer will be a fat pointer whose
metadata is a vtable that tells you what kind of struct it is.

Heterogeneous lists are heavily used by Rust Binder. There are a lot of
so-called todo lists containing various events that need to be delivered
to userspace next time userspace calls into the driver. And there are
quite a few different todo item types: incoming transaction, changes to
refcounts, death notifications, and more.

Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240814-linked-list-v5-9-f5f5e8075da0@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
rust: list: add macro for implementing ListItem 2024-08-23T04:26:57+00:00 Alice Ryhl aliceryhl@google.com 2024-08-14T08:05:24+00:00 40c53294596b4a7fe2ae126d7aab986752496c31 Adds a macro for safely implementing the ListItem trait. As part of the implementation of the macro, we also provide a HasListLinks trait similar to the workqueue's HasWorkItem trait. The HasListLinks trait is only necessary if you are implementing ListItem using the impl_list_item macro. Reviewed-by: Benno Lossin <benno.lossin@proton.me> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240814-linked-list-v5-5-f5f5e8075da0@google.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org> 
Adds a macro for safely implementing the ListItem trait. As part of the
implementation of the macro, we also provide a HasListLinks trait
similar to the workqueue's HasWorkItem trait.

The HasListLinks trait is only necessary if you are implementing
ListItem using the impl_list_item macro.

Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240814-linked-list-v5-5-f5f5e8075da0@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>