[PATCH v3 3/5] samples: rust: Provide example using the new Rust MiscDevice abstraction

Lee Jones
2024-12-06T09:05:49Z

This sample driver demonstrates the following basic operations:

* Register a Misc Device
* Create /dev/rust-misc-device
* Open the aforementioned character device
* Operate on the character device via a simple ioctl()
* Close the character device

Signed-off-by: Lee Jones <lee@kernel.org>
---
samples/rust/Kconfig | 10 ++++
samples/rust/Makefile | 1 +
samples/rust/rust_misc_device.rs | 80 ++++++++++++++++++++++++++++++++
3 files changed, 91 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..f50925713f1a
--- /dev/null
+++ b/samples/rust/rust_misc_device.rs
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Rust misc device sample.
+
+use kernel::{
+ c_str,
+ ioctl::_IO,
+ miscdevice::{MiscDevice, MiscDeviceOptions, MiscDeviceRegistration},
+ prelude::*,
+};
+
+const RUST_MISC_DEV_HELLO: u32 = _IO('R' as u32, 9);
+
+module! {
+ type: RustMiscDeviceModule,
+ name: "rust_misc_device",
+ author: "Lee Jones",
+ description: "Rust misc device sample",
+ license: "GPL",
+}
+
+struct RustMiscDeviceModule {
+ _miscdev: Pin<KBox<MiscDeviceRegistration<RustMiscDevice>>>,
+}
+
+impl kernel::Module for RustMiscDeviceModule {
+ fn init(_module: &'static ThisModule) -> Result<Self> {
+ pr_info!("Initialising Rust Misc Device Sample\n");
+
+ let options = MiscDeviceOptions {
+ name: c_str!("rust-misc-device"),
+ };
+
+ Ok(Self {
+ _miscdev: KBox::pin_init(
+ MiscDeviceRegistration::<RustMiscDevice>::register(options),
+ GFP_KERNEL,
+ )?,
+ })
+ }
+}
+
+struct RustMiscDevice;
+
+#[vtable]
+impl MiscDevice for RustMiscDevice {
+ type Ptr = KBox<Self>;
+
+ fn open() -> Result<KBox<Self>> {
+ pr_info!("Opening Rust Misc Device Sample\n");
+
+ Ok(KBox::new(RustMiscDevice, GFP_KERNEL)?)
+ }
+
+ fn ioctl(
+ _device: <Self::Ptr as kernel::types::ForeignOwnable>::Borrowed<'_>,
+ cmd: u32,
+ _arg: usize,
+ ) -> Result<isize> {
+ pr_info!("IOCTLing Rust Misc Device Sample\n");
+
+ match cmd {
+ RUST_MISC_DEV_HELLO => pr_info!("Hello from the Rust Misc Device\n"),
+ _ => {
+ pr_err!("IOCTL not recognised: {}\n", cmd);
+ return Err(ENOIOCTLCMD);
+ }
+ }
+
+ Ok(0)
+ }
+}
+
+impl Drop for RustMiscDevice {
+ fn drop(&mut self) {
+ pr_info!("Exiting the Rust Misc Device Sample\n");
+ }
+}
--
2.47.0.338.g60cca15819-goog