8909a80e3f
The `Cow` type [1] requires that its generic parameter type implements the `ToOwned` trait [2], which provides a method to create owned data from borrowed data, usually by cloning. However, it is infallible, and thus in most cases it is not useful for the kernel. [3] Therefore, introduce `cfg(no_borrow)` to remove the `borrow` module (which contains `ToOwned` and `Cow`) from `alloc`. Link: https://doc.rust-lang.org/alloc/borrow/enum.Cow.html [1] Link: https://doc.rust-lang.org/alloc/borrow/trait.ToOwned.html [2] Link: https://lore.kernel.org/rust-for-linux/20221204103153.117675b1@GaryWorkstation/ [3] Cc: Gary Guo <gary@garyguo.net> Cc: Wedson Almeida Filho <wedsonaf@gmail.com> Cc: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Miguel Ojeda <ojeda@kernel.org> Reviewed-by: Wei Liu <wei.liu@kernel.org> Reviewed-by: Finn Behrens <fin@nyantec.com> |
||
|---|---|---|
| .. | ||
| collections | ||
| vec | ||
| alloc.rs | ||
| boxed.rs | ||
| lib.rs | ||
| raw_vec.rs | ||
| README.md | ||
| slice.rs | ||
alloc
These source files come from the Rust standard library, hosted in the https://github.com/rust-lang/rust repository, licensed under "Apache-2.0 OR MIT" and adapted for kernel use. For copyright details, see https://github.com/rust-lang/rust/blob/master/COPYRIGHT.
Please note that these files should be kept as close as possible to upstream. In general, only additions should be performed (e.g. new methods). Eventually, changes should make it into upstream so that, at some point, this fork can be dropped from the kernel tree.
Rationale
On one hand, kernel folks wanted to keep alloc in-tree to have more
freedom in both workflow and actual features if actually needed
(e.g. receiver types if we ended up using them), which is reasonable.
On the other hand, Rust folks wanted to keep alloc as close as
upstream as possible and avoid as much divergence as possible, which
is also reasonable.
We agreed on a middle-ground: we would keep a subset of alloc
in-tree that would be as small and as close as possible to upstream.
Then, upstream can start adding the functions that we add to alloc
etc., until we reach a point where the kernel already knows exactly
what it needs in alloc and all the new methods are merged into
upstream, so that we can drop alloc from the kernel tree and go back
to using the upstream one.
By doing this, the kernel can go a bit faster now, and Rust can slowly incorporate and discuss the changes as needed.