Re: [PATCH v8 1/1] rust: introduce abstractions for fwctl

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Aug 13, 2026 at 06:23:12PM +0300, Zhi Wang wrote:
> Introduce safe Rust wrappers around struct fwctl_device and
> struct fwctl_uctx. This lets Rust drivers register fwctl devices and
> implement firmware RPC callbacks through a typed trait interface.
> 
> The abstraction keeps lifetime and reference-count handling inside the
> wrapper, exposes pinned per-FD user contexts to drivers, and validates the
> layout assumptions required by the C fwctl allocation model. Allocation
> sizes are padded so the kmalloc-backed C allocations also satisfy Rust
> alignment requirements.
> 
> Registration owns driver private data with a lifetime tied to the bound
> parent device and verifies the parent identity before registration.
> Callbacks access that data through a higher-ranked closure, preventing its
> erased lifetime from escaping, while Device remains only the refcounted
> fwctl object. This avoids requiring Rust drop glue from the fwctl_device
> release path after unregister or module teardown.
> 
> RPC callbacks receive typed scope information, a mutable request/response
> buffer, and the userspace output-buffer size. Response pointer conversion,
> length validation, and raw output-length handling remain inside the
> abstraction.
> 
> Add the Rust sources to the FWCTL MAINTAINERS entry and add myself as the
> maintainer for the Rust abstractions.
> 
> Co-developed-by: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> Link: https://lore.kernel.org/r/DJJW7X4ESDSM.QCVYK2FC7ZR3@kernel.org
> Signed-off-by: Zhi Wang <zhiw@nvidia.com>
> ---
>  MAINTAINERS                     |   3 +
>  drivers/fwctl/Kconfig           |  12 +
>  rust/bindings/bindings_helper.h |   1 +
>  rust/helpers/fwctl.c            |  17 +
>  rust/helpers/helpers.c          |   3 +-
>  rust/kernel/fwctl.rs            | 593 ++++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs              |   2 +
>  7 files changed, 630 insertions(+), 1 deletion(-)
>  create mode 100644 rust/helpers/fwctl.c
>  create mode 100644 rust/kernel/fwctl.rs

Applied thanks, I was eventually able to get things here so it can
compile even.

Jason