Re: [PATCH v6 2/5] samples: rust: Provide example using the new Rust MiscDevice abstraction

[Danilo Krummrich <dakr@kernel.org>]

On Fri, Dec 13, 2024 at 01:47:07PM +0000, Lee Jones wrote:
> This sample driver demonstrates the following basic operations:
> 
> * Register a Misc Device
> * Create /dev/rust-misc-device
> * Provide open call-back for the aforementioned character device
> * Operate on the character device via a simple ioctl()
> * Provide close call-back for the character device
> 
> Signed-off-by: Lee Jones <lee@kernel.org>

Reviewed-by: Danilo Krummrich <dakr@kernel.org>

> ---
>  samples/rust/Kconfig             | 10 ++++
>  samples/rust/Makefile            |  1 +
>  samples/rust/rust_misc_device.rs | 87 ++++++++++++++++++++++++++++++++
>  3 files changed, 98 insertions(+)
>  create mode 100644 samples/rust/rust_misc_device.rs
> 
> diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
> index b0f74a81c8f9..df384e679901 100644
> --- a/samples/rust/Kconfig
> +++ b/samples/rust/Kconfig
> @@ -20,6 +20,16 @@ config SAMPLE_RUST_MINIMAL
>  
>  	  If unsure, say N.
>  
> +config SAMPLE_RUST_MISC_DEVICE
> +	tristate "Misc device"
> +	help
> +	  This option builds the Rust misc device.
> +
> +	  To compile this as a module, choose M here:
> +	  the module will be called rust_misc_device.
> +
> +	  If unsure, say N.
> +
>  config SAMPLE_RUST_PRINT
>  	tristate "Printing macros"
>  	help
> diff --git a/samples/rust/Makefile b/samples/rust/Makefile
> index c1a5c1655395..ad4b97a98580 100644
> --- a/samples/rust/Makefile
> +++ b/samples/rust/Makefile
> @@ -2,6 +2,7 @@
>  ccflags-y += -I$(src)				# needed for trace events
>  
>  obj-$(CONFIG_SAMPLE_RUST_MINIMAL)		+= rust_minimal.o
> +obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE)		+= rust_misc_device.o
>  obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o
>  
>  rust_print-y := rust_print_main.o rust_print_events.o
> diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
> new file mode 100644
> index 000000000000..324c3696ae3f
> --- /dev/null
> +++ b/samples/rust/rust_misc_device.rs
> @@ -0,0 +1,87 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! Rust misc device sample.
> +
> +use kernel::{
> +    c_str,
> +    device::Device,
> +    fs::File,
> +    ioctl::_IO,
> +    miscdevice::{MiscDevice, MiscDeviceOptions, MiscDeviceRegistration},
> +    prelude::*,
> +    types::ARef,
> +};
> +
> +const RUST_MISC_DEV_HELLO: u32 = _IO('|' as u32, 0x80);
> +
> +module! {
> +    type: RustMiscDeviceModule,
> +    name: "rust_misc_device",
> +    author: "Lee Jones",
> +    description: "Rust misc device sample",
> +    license: "GPL",
> +}
> +
> +#[pin_data]
> +struct RustMiscDeviceModule {
> +    #[pin]
> +    _miscdev: MiscDeviceRegistration<RustMiscDevice>,
> +}
> +
> +impl kernel::InPlaceModule for RustMiscDeviceModule {
> +    fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
> +        pr_info!("Initialising Rust Misc Device Sample\n");
> +
> +        let options = MiscDeviceOptions {
> +            name: c_str!("rust-misc-device"),
> +        };
> +
> +        try_pin_init!(Self {
> +            _miscdev <- MiscDeviceRegistration::register(options),
> +        })
> +    }
> +}
> +
> +struct RustMiscDevice {
> +    dev: ARef<Device>,
> +}
> +
> +#[vtable]
> +impl MiscDevice for RustMiscDevice {
> +    type Ptr = KBox<Self>;
> +
> +    fn open(_file: &File, misc: &MiscDeviceRegistration<Self>) -> Result<KBox<Self>> {
> +        let dev = ARef::from(misc.device());
> +
> +        dev_info!(dev, "Opening Rust Misc Device Sample\n");
> +
> +        Ok(KBox::new(RustMiscDevice { dev }, GFP_KERNEL)?)
> +    }
> +
> +    fn ioctl(
> +        me: <Self::Ptr as kernel::types::ForeignOwnable>::Borrowed<'_>,
> +        _file: &File,
> +        cmd: u32,
> +        _arg: usize,
> +    ) -> Result<isize> {
> +        dev_info!(me.dev, "IOCTLing Rust Misc Device Sample\n");
> +
> +        match cmd {
> +            RUST_MISC_DEV_HELLO => dev_info!(me.dev, "Hello from the Rust Misc Device\n"),
> +            _ => {
> +                dev_err!(me.dev, "-> IOCTL not recognised: {}\n", cmd);
> +                return Err(ENOTTY);
> +            }
> +        }
> +
> +        Ok(0)
> +    }
> +}
> +
> +impl Drop for RustMiscDevice {
> +    fn drop(&mut self) {
> +        dev_info!(self.dev, "Exiting the Rust Misc Device Sample\n");
> +    }
> +}
> -- 
> 2.47.1.613.gc27f4b7a9f-goog
> 
>