Re: [PATCH 0/5] use custom FFI integer types

[Benno Lossin <benno.lossin@proton.me>]

On 13.09.24 23:29, Gary Guo wrote:
> This patch series aim to reduce the unnecessary type casts needed in
> Rust code doing FFI calls.
> 
> With this series, we can ensure:
> 
> * `size_t` is mapped to usize. Currently this is mostly true except for
>   C builtin functions, which gets translated by bindgen to c_ulong/c_uint.
> 
> * `__kernel_size_t` is mapped to usize. Currently this is mapped to
>   c_ulong/c_uint.
> 
> * `unsigned long` is mapped to usize. Currently this is mapped by Rust
>   libcore to either u32 or u64.
> 
> * `char` is mapped to `u8`. Currently this is mapped by Rust libcore to
>   either i8 or u8.

Great work!

> After this series, FFI code needs to use `kernel::ffi` types instead of
> `core::ffi`.

I think we should have a lint that checks for this. Can probably be a
checkpatch.pl check and a good-first-issue.

---
Cheers,
Benno

> Gary Guo (5):
>   rust: fix size_t in bindgen prototypes of C builtins
>   rust: map `__kernel_size_t` and friends also to usize/isize
>   rust: use custom FFI integer types
>   rust: map `long` to `isize` and `char` to `u8`
>   rust: cleanup unnecessary casts
> 
>  rust/Makefile                      | 24 ++++++++++-----
>  rust/bindgen_parameters            |  5 ++++
>  rust/bindings/lib.rs               |  5 ++++
>  rust/ffi.rs                        | 48 ++++++++++++++++++++++++++++++
>  rust/kernel/alloc/allocator.rs     |  4 +--
>  rust/kernel/block/mq/operations.rs | 18 +++++------
>  rust/kernel/block/mq/raw_writer.rs |  2 +-
>  rust/kernel/block/mq/tag_set.rs    |  2 +-
>  rust/kernel/error.rs               | 25 +++++++---------
>  rust/kernel/firmware.rs            |  2 +-
>  rust/kernel/init.rs                |  2 +-
>  rust/kernel/kunit.rs               | 10 ++-----
>  rust/kernel/lib.rs                 |  2 ++
>  rust/kernel/net/phy.rs             | 14 ++++-----
>  rust/kernel/print.rs               |  4 +--
>  rust/kernel/str.rs                 | 10 +++----
>  rust/kernel/sync/arc.rs            |  6 ++--
>  rust/kernel/sync/condvar.rs        |  2 +-
>  rust/kernel/sync/lock.rs           |  2 +-
>  rust/kernel/sync/lock/mutex.rs     |  2 +-
>  rust/kernel/sync/lock/spinlock.rs  |  2 +-
>  rust/kernel/task.rs                |  8 ++---
>  rust/kernel/time.rs                |  4 +--
>  rust/kernel/types.rs               | 26 ++++++++--------
>  rust/kernel/uaccess.rs             | 31 ++++++-------------
>  rust/macros/module.rs              |  8 ++---
>  rust/uapi/lib.rs                   |  5 ++++
>  27 files changed, 161 insertions(+), 112 deletions(-)
>  create mode 100644 rust/ffi.rs
> 
> 
> base-commit: 93dc3be19450447a3a7090bd1dfb9f3daac3e8d2
> --
> 2.44.1
>