linux/rust/helpers/fwctl.c
Zhi Wang e052daab94 rust: introduce abstractions for fwctl
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.

Link: https://patch.msgid.link/r/20260813152312.1311142-2-zhiw@nvidia.com
Co-developed-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2026-08-14 19:21:17 -03:00

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C

// SPDX-License-Identifier: GPL-2.0
#include <linux/fwctl.h>
#if IS_ENABLED(CONFIG_RUST_FWCTL_ABSTRACTIONS)
__rust_helper struct fwctl_device *rust_helper_fwctl_get(struct fwctl_device *fwctl)
{
return fwctl_get(fwctl);
}
__rust_helper void rust_helper_fwctl_put(struct fwctl_device *fwctl)
{
fwctl_put(fwctl);
}
#endif