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Currently we have several lines of work:
- Integrating with the kernel tree and build system (Nick's & mine,
both uploaded as branches, based on `rustc`; and another one I have
been working on, based on `cargo`).
- Bindings and the first bits of functionality (Alex's & Geoffrey's,
based on `cargo`).
This patch effectively merges the work we have been doing and
integrates it in the latest mainline kernel tree.
This does *not* mean anything needs to stay as-is, but this gives us
a working, common base to work and experiment upon. Hopefully, it will
also attract external people to join!
As a summary, I added:
- `cargo` integration with the kernel `Makefile`s:
+ Virtual `cargo` workspace to have a single lock file and to share
deps between `cargo` jobs.
+ Picks the same optimization level as configured for C.
+ Verbose output on `V=1`.
+ A `cargoclean` target to clean all the Rust-related artifacts.
- Initial support for built-in modules (i.e. `Y` as well as `M`):
+ It is a hack, we need to implement a few things (see the `TODO`s),
but it is enough to start playing with things that depend on `MODULE`.
+ Passes `--cfg module` to built-in modules to be able to compile
conditionally inside Rust.
+ Increased `KSYM_NAME_LEN` length to avoid warnings due to Rust
long mangled symbols.
- Rust infrastructure in a new top level folder `rust/`:
+ A `kernel` package which contains the sources from Alex &
Geoffrey's work plus some changes:
* Adapted `build.rs`.
* Removed the `THIS_MODULE` emulation until it is implemented.
* Removed `Makefile` logic and the code that `cfg`-depended
on kernel version (no need in mainline).
* Moved the helpers to be triggered via normal compilation,
renamed them under `rust_*` and exported via
`EXPORT_SYMBOL` instead.
* Added a prelude.
+ A `shlex` package which serves as an example of an "inline"
dependency (i.e. package checked out copy to avoid the network)
- The example driver was setup at `drivers/char/rust_example/`.
- Misc
+ The beginning of `Documentation/rust/` with a quick start guide.
+ `MAINTAINERS` entry.
+ SPDXs for all files.
Other notes that aren't in `TODO`s:
- We could minimize the network requirements (use `bindgen` binary, use more
inline dependencies...), but it is not clear it would be a good idea for
the moment due to `core`/`alloc`/`compiler-builtins`.
- The intention of `rust/` is to have a place to put extra dependencies
and split the `kernel` package into several in the future if it grows.
It could resemble the usual kernel tree structure.
- With several drivers being built-in, `cargo` recompiles `kernel`
and triggers duplicate symbol errors when merging thin archives.
We need to make it only compile `kernel` once.
- When the above works, then `make`'s `-j` calling concurrent `cargo`s
(e.g. several drivers at the same time) should be OK, I think.
According to https://github.com/rust-lang/cargo/pull/2486 it shouldn't
miscompile anything, but if they start locking on each other
we will have make jobs waiting that could have been doing something else.
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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