Feat Request: Support exporting RROS interfaces to C drivers via C ABI and generated headers

[ruiqurm]

Background

Currently, to develop a driver using the RROS service, developers are required to implement it in Rust under the rros/ directory. However, in real-world usage, most existing drivers are written in C and we usually only need limited access to RROS functionality (e.g., files, thread, memory buffers) to enable out-of-band (OOB) execution.

Rewriting these drivers entirely in Rust is impractical and unnecessary. Instead, a more viable path is to allow existing C drivers to directly call RROS functions and use RROS-defined structs with minimal modifications. This, however, currently lacks proper tooling and support in the build system.

Feature Request

Introduce a mechanism that allows RROS to expose selected functions and data structures via a C-compatible ABI, and generate a corresponding C header file. This will enable C drivers to:

• Include RROS headers (#include <rros.h>)
• Link against RROS-exported symbols
• Use RROS struct definitions in a type-safe manner
  In advance, we could have a macro to wrap this things together.

Proposed Design

Rust-side ABI exposure:

• Use #[repr(C)] for structs and #[no_mangle] extern "C" for functions in a dedicated rros_ffi module.

#[repr(C)]
pub struct RrosFoo{
    filp: *mut bindings::file,
}

#[no_mangle]
pub extern "C" fn rros_open_file(rf: *mut RrosFoo) ->i32{
      // Some rros service functions
      0
}

• Header file generation:
  Use bindgen to generate a rros.h header from the module.
  Integrate this into the kernel build process (e.g., as a pre-build step in scripts/Makefile.build).
• Add a RROS c glue layer.
  Add a c file, say rros_export.c. Add the exported function automatically:

extern int rros_open_file(struct RrosFoo *rf);

EXPORT_SYMBOL(rros_open_file);

• Integration with kernel build system:
  Install the generated header into include/generated/ or another suitable path.

Benefits

• Greatly simplifies OOB adaptation of existing C drivers.
• Aligns with existing kernel practices (e.g., EXPORT_SYMBOL, generated headers).

Optional Extensions

• Use versioning macros in rros.h to manage API evolution.
• Use macro and Makefile script to automatically finish the work.