[RFC 0/2] rust: introduce abstractions for fwctl

[Zhi Wang <zhiw@nvidia.com>]

In the NVIDIA vGPU RFC [1], the vGPU type blobs must be provided to the GSP
before userspace can enumerate available vGPU types and create vGPU
instances. The original design relied on the firmware loading interface,
but fwctl is a more natural fit for this use case, as it is designed for
uploading configuration or firmware data required before the device becomes
operational.

This patch introduces a Rust abstraction over the fwctl subsystem,
providing safe and idiomatic bindings.

The new `fwctl` module allows Rust drivers to integrate with the existing
C-side fwctl core through a typed trait interface. It provides:

  - `FwCtlOps` trait — defines driver-specific operations such as
    `open_uctx()`, `close_uctx()`, `info()`, and `fw_rpc()`.  
    Each Rust driver implements this trait to describe its own per-FD
    user-context behavior and RPC handling.

  - `FwCtlUCtx<T>` — a generic wrapper around `struct fwctl_uctx`
    embedding driver-specific context data, providing safe conversion
    from raw C pointers and access to the parent device.

  - `Registration<T>` — safe registration and automatic unregistration
    of `struct fwctl_device` objects using the kernel’s device model.

  - `FwCtlVTable<T>` — a static vtable bridging C callbacks and Rust
    trait methods, ensuring type safety across the FFI boundary.

`rust/kernel/lib.rs` is updated to conditionally include this module
under `CONFIG_FWCTL`.

[1] https://lore.kernel.org/all/20250903221111.3866249-1-zhiw@nvidia.com/

Zhi Wang (2):
  rust: introduce abstractions for fwctl
  samples: rust: fwctl: add sample code for FwCtl

 include/uapi/fwctl/fwctl.h        |   1 +
 rust/bindings/bindings_helper.h   |   1 +
 rust/kernel/fwctl.rs              | 254 ++++++++++++++++++++++++++++++
 rust/kernel/lib.rs                |   2 +
 samples/rust/Kconfig              |  11 ++
 samples/rust/Makefile             |   1 +
 samples/rust/rust_driver_fwctl.rs | 123 +++++++++++++++
 7 files changed, 393 insertions(+)
 create mode 100644 rust/kernel/fwctl.rs
 create mode 100644 samples/rust/rust_driver_fwctl.rs

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2.47.3