Re: [PATCH v2 2/2] samples: rust: fwctl: add sample code for fwctl

["Gary Guo" <gary@garyguo.net>]

On Thu Jan 22, 2026 at 8:42 PM GMT, Zhi Wang wrote:
> This patch adds a sample Rust driver demonstrating the usage of the fwctl
> Rust abstractions. Add sample code for creating a FwCtl device, getting
> device info and issuing an RPC.
>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Zhi Wang <zhiw@nvidia.com>
> ---
>  samples/rust/Kconfig              |  11 +++
>  samples/rust/Makefile             |   1 +
>  samples/rust/rust_driver_fwctl.rs | 136 ++++++++++++++++++++++++++++++
>  3 files changed, 148 insertions(+)
>  create mode 100644 samples/rust/rust_driver_fwctl.rs
>
> diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
> index c49ab9106345..3d0b223caa89 100644
> --- a/samples/rust/Kconfig
> +++ b/samples/rust/Kconfig
> @@ -172,6 +172,17 @@ config SAMPLE_RUST_SOC
>  
>  	  If unsure, say N.
>  
> +config SAMPLE_RUST_DRIVER_FWCTL
> +	tristate "Fwctl Driver"
> +	depends on FWCTL
> +	help
> +	  This option builds the Rust Fwctl driver sample.
> +
> +	  To compile this as a module, choose M here:
> +	  the module will be called rust_driver_fwctl.
> +
> +	  If unsure, say N.
> +
>  config SAMPLE_RUST_HOSTPROGS
>  	bool "Host programs"
>  	help
> diff --git a/samples/rust/Makefile b/samples/rust/Makefile
> index 6c0aaa58cccc..6f6030e64727 100644
> --- a/samples/rust/Makefile
> +++ b/samples/rust/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM)	+= rust_driver_platform.o
>  obj-$(CONFIG_SAMPLE_RUST_DRIVER_USB)		+= rust_driver_usb.o
>  obj-$(CONFIG_SAMPLE_RUST_DRIVER_FAUX)		+= rust_driver_faux.o
>  obj-$(CONFIG_SAMPLE_RUST_DRIVER_AUXILIARY)	+= rust_driver_auxiliary.o
> +obj-$(CONFIG_SAMPLE_RUST_DRIVER_FWCTL)		+= rust_driver_fwctl.o
>  obj-$(CONFIG_SAMPLE_RUST_CONFIGFS)		+= rust_configfs.o
>  obj-$(CONFIG_SAMPLE_RUST_SOC)			+= rust_soc.o
>  
> diff --git a/samples/rust/rust_driver_fwctl.rs b/samples/rust/rust_driver_fwctl.rs
> new file mode 100644
> index 000000000000..ac5f979fd73b
> --- /dev/null
> +++ b/samples/rust/rust_driver_fwctl.rs
> @@ -0,0 +1,136 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Rust fwctl API test (based on QEMU's `pci-testdev`).
> +//!
> +//! To make this driver probe, QEMU must be run with `-device pci-testdev`.
> +
> +use kernel::{
> +    bindings,
> +    device,
> +    device::Core,
> +    devres::Devres,
> +    fwctl,
> +    pci,
> +    prelude::*,
> +    sync::aref::ARef,
> +    types,
> +};
> +
> +struct FwctlSampleUserCtx {
> +    _drvdata: u32,
> +}
> +
> +struct FwctlSampleOps;
> +
> +impl fwctl::Operations for FwctlSampleOps {
> +    type UserCtx = FwctlSampleUserCtx;
> +
> +    const DEVICE_TYPE: fwctl::DeviceType = fwctl::DeviceType::RustFwctlTest;
> +
> +    fn open(
> +        fwctl_uctx: &types::Opaque<bindings::fwctl_uctx>
> +    ) -> Result<impl PinInit<Self::UserCtx, Error>, Error> {
> +        let dev = fwctl::UserCtx::<Self::UserCtx>::parent_device_from_raw(fwctl_uctx);

Why does this raw binding need to be handled by the user?

> +
> +        dev_info!(dev, "fwctl test driver: open_uctx()");
> +
> +        // Return an initializer for the user context.
> +        // The framework will initialize this in-place in the C-allocated memory.
> +        Ok(try_init!(FwctlSampleUserCtx {
> +            _drvdata: 0,
> +        }))
> +    }
> +
> +    fn close(uctx: &mut fwctl::UserCtx<FwctlSampleUserCtx>) {
> +        let dev = uctx.get_parent_device();
> +
> +        dev_info!(dev, "fwctl test driver: close_uctx()");
> +    }
> +
> +    fn info(uctx: &mut fwctl::UserCtx<FwctlSampleUserCtx>) -> Result<KVec<u8>, Error> {

This can just be `Result<KVec<u8>>`.

Best,
Gary

> +        let dev = uctx.get_parent_device();
> +
> +        dev_info!(dev, "fwctl test driver: info()");
> +
> +        let mut infobuf = KVec::<u8>::new();
> +        infobuf.push(0xef, GFP_KERNEL)?;
> +        infobuf.push(0xbe, GFP_KERNEL)?;
> +        infobuf.push(0xad, GFP_KERNEL)?;
> +        infobuf.push(0xde, GFP_KERNEL)?;
> +
> +        Ok(infobuf)
> +    }
> +
> +    fn fw_rpc(
> +        uctx: &mut fwctl::UserCtx<FwctlSampleUserCtx>,
> +        scope: u32,
> +        rpc_in: &mut [u8],
> +        _out_len: *mut usize,
> +    ) -> Result<Option<KVec<u8>>, Error> {
> +        let dev = uctx.get_parent_device();
> +
> +        dev_info!(dev, "fwctl test driver: fw_rpc() scope {}", scope);
> +
> +        if rpc_in.len() != 4 {
> +            return Err(EINVAL);
> +        }
> +
> +        dev_info!(
> +            dev,
> +            "fwctl test driver: inbuf len{} bytes[0-3] {:x} {:x} {:x} {:x}",
> +            rpc_in.len(),
> +            rpc_in[0],
> +            rpc_in[1],
> +            rpc_in[2],
> +            rpc_in[3]
> +        );
> +
> +        let mut outbuf = KVec::<u8>::new();
> +        outbuf.push(0xef, GFP_KERNEL)?;
> +        outbuf.push(0xbe, GFP_KERNEL)?;
> +        outbuf.push(0xad, GFP_KERNEL)?;
> +        outbuf.push(0xde, GFP_KERNEL)?;
> +
> +        Ok(Some(outbuf))
> +    }
> +}
> +
> +#[pin_data]
> +struct FwctlSampleDriver {
> +    pdev: ARef<pci::Device>,
> +    #[pin]
> +    fwctl: Devres<fwctl::Registration<FwctlSampleOps>>,
> +}
> +
> +kernel::pci_device_table!(
> +    PCI_TABLE,
> +    MODULE_PCI_TABLE,
> +    <FwctlSampleDriver as pci::Driver>::IdInfo,
> +    [(pci::DeviceId::from_id(pci::Vendor::REDHAT, 0x5), ())]
> +);
> +
> +impl pci::Driver for FwctlSampleDriver {
> +    type IdInfo = ();
> +    const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
> +
> +    fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> impl PinInit<Self, Error> {
> +        dev_info!(pdev.as_ref(), "Probe fwctl test driver");
> +
> +        // `pdev` is `Device<Core>`, which derefs to `Device<Bound>` during probe.
> +        let pdev_bound: &pci::Device<device::Bound> = pdev;
> +
> +        try_pin_init!(Self {
> +            pdev: pdev.into(),
> +            fwctl <- fwctl::Registration::<FwctlSampleOps>::new(pdev_bound.as_ref()),
> +        })
> +    }
> +}
> +
> +kernel::module_pci_driver! {
> +    type: FwctlSampleDriver,
> +    name: "rust_driver_fwctl",
> +    authors: ["Zhi Wang"],
> +    description: "Rust fwctl test",
> +    license: "GPL v2",
> +    imports_ns: ["FWCTL"],
> +}