linux-kernel - Re: [PATCH v2 0/2] rust: introduce abstractions for fwctl

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Message-Id: <DFVFTMRD9LM8.HGKSL57RYD1D@kernel.org>
Date: Thu, 22 Jan 2026 22:32:03 +0100
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Zhi Wang" <zhiw@...dia.com>
Cc: <rust-for-linux@...r.kernel.org>, <linux-pci@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <aliceryhl@...gle.com>,
 <bhelgaas@...gle.com>, <kwilczynski@...nel.org>, <ojeda@...nel.org>,
 <alex.gaynor@...il.com>, <boqun.feng@...il.com>, <gary@...yguo.net>,
 <bjorn3_gh@...tonmail.com>, <lossin@...nel.org>, <a.hindborg@...nel.org>,
 <tmgross@...ch.edu>, <markus.probst@...teo.de>, <helgaas@...nel.org>,
 <cjia@...dia.com>, <smitra@...dia.com>, <ankita@...dia.com>,
 <aniketa@...dia.com>, <kwankhede@...dia.com>, <targupta@...dia.com>,
 <acourbot@...dia.com>, <joelagnelf@...dia.com>, <jhubbard@...dia.com>,
 <zhiwang@...nel.org>, <daniel.almeida@...labora.com>, "Jason Gunthorpe"
 <jgg@...dia.com>
Subject: Re: [PATCH v2 0/2] rust: introduce abstractions for fwctl

(Cc: Jason)

Looks like you used the recipient list of another patch series by accident. :)

On Thu Jan 22, 2026 at 9:42 PM CET, Zhi Wang wrote:
> 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:
>
>   - `Operations` 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.
>
>   - `UserCtx<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.
>
>   - `VTable<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`.
>
> The repo with the patches can be found at [2].
>
> v2:
>
> - Don't open fwctl_put(). Add a rust helper. (Jason/Danilo)
> - Wrap Registration with Devres to guarantee proper lifetime management.
>   (Jason/Danilo)
> - Rename FwctlOps to Operations, FwctlUserCtx to UserCtx, FwctlDevice to
>   Device. (Danilo)
> - Use fwctl::DeviceType enum instead of raw u32 for DEVICE_TYPE. (Danilo)
> - Change fwctl_uctx field in UserCtx to Opaque<bindings::fwctl_uctx> and
>   make it private. (Danilo)
> - Provide Deref and DerefMut implementations for UserCtx::uctx. (Danilo)
> - Add UserCtx::parent_device_from_raw() to simplify parent device access.
> - Use cast() and cast_mut() instead of manual pointer casts. (Danilo)
> - Implement AlwaysRefCounted for Device and use ARef<Device> in
>   Registration. (Danilo)
> - Add rust_helper_fwctl_get() for reference counting.
> - Improve safety comments for slice::from_raw_parts_mut() in
>   fw_rpc_callback. (Danilo)
> - Convert imports to vertical style.
> - Fix all clippy warnings.
>
> v1:
>
> - Initial submission introducing fwctl Rust abstractions.
>
> [1] https://lore.kernel.org/all/20250903221111.3866249-1-zhiw@nvidia.com/
> [2] https://github.com/zhiwang-nvidia/driver-core/tree/fwctl-rust-abstraction-v2
>
> Zhi Wang (2):
>   rust: introduce abstractions for fwctl
>   samples: rust: fwctl: add sample code for fwctl
>
>  drivers/fwctl/Kconfig             |  12 +
>  include/uapi/fwctl/fwctl.h        |   1 +
>  rust/bindings/bindings_helper.h   |   1 +
>  rust/helpers/fwctl.c              |  17 ++
>  rust/helpers/helpers.c            |   3 +-
>  rust/kernel/fwctl.rs              | 456 ++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs                |   2 +
>  samples/rust/Kconfig              |  11 +
>  samples/rust/Makefile             |   1 +
>  samples/rust/rust_driver_fwctl.rs | 136 +++++++++
>  10 files changed, 639 insertions(+), 1 deletion(-)
>  create mode 100644 rust/helpers/fwctl.c
>  create mode 100644 rust/kernel/fwctl.rs
>  create mode 100644 samples/rust/rust_driver_fwctl.rs
>
> -- 
> 2.51.0