* [PATCH v13 1/3] rust: add basic serial device bus abstractions
2026-07-12 16:58 [PATCH v13 0/3] rust: add basic serial device bus abstractions Markus Probst
@ 2026-07-12 16:58 ` Markus Probst
2026-07-12 17:15 ` sashiko-bot
2026-07-12 16:58 ` [PATCH v13 2/3] samples: rust: add Rust serial device bus sample device driver Markus Probst
2026-07-12 16:58 ` [PATCH v13 3/3] MAINTAINERS: serdev: Add self for serdev Markus Probst
2 siblings, 1 reply; 6+ messages in thread
From: Markus Probst @ 2026-07-12 16:58 UTC (permalink / raw)
To: Rob Herring, Greg Kroah-Hartman, Jiri Slaby, Miguel Ojeda,
Gary Guo, Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Kari Argillander,
Rafael J. Wysocki, Viresh Kumar, Boqun Feng, David Airlie,
Simona Vetter, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, Boqun Feng
Cc: linux-serial, linux-kernel, rust-for-linux, linux-pm, driver-core,
dri-devel, Markus Probst
Implement the basic serial device bus abstractions required to write a
serial device bus device driver with or without the need for initial device
data. This includes the following data structures:
The `serdev::Driver` trait represents the interface to the driver.
The `serdev::Device` abstraction represents a `struct serdev_device`.
In order to provide the Serdev specific parts to a generic
`driver::Registration` the `driver::RegistrationOps` trait is
implemented by `serdev::Adapter`.
Signed-off-by: Markus Probst <markus.probst@posteo.de>
---
MAINTAINERS | 2 +
drivers/tty/serdev/Kconfig | 7 +
rust/bindings/bindings_helper.h | 1 +
rust/helpers/helpers.c | 1 +
rust/helpers/serdev.c | 22 ++
rust/kernel/lib.rs | 2 +
rust/kernel/serdev.rs | 590 ++++++++++++++++++++++++++++++++++++++++
7 files changed, 625 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 4a8b0fd665ce..00d977ce7028 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -24567,6 +24567,8 @@ S: Maintained
F: Documentation/devicetree/bindings/serial/serial.yaml
F: drivers/tty/serdev/
F: include/linux/serdev.h
+F: rust/helpers/serdev.c
+F: rust/kernel/serdev.rs
SERIAL IR RECEIVER
M: Sean Young <sean@mess.org>
diff --git a/drivers/tty/serdev/Kconfig b/drivers/tty/serdev/Kconfig
index 46ae732bfc68..e6dfe949ad01 100644
--- a/drivers/tty/serdev/Kconfig
+++ b/drivers/tty/serdev/Kconfig
@@ -9,6 +9,13 @@ menuconfig SERIAL_DEV_BUS
Note that you typically also want to enable TTY port controller support.
+config RUST_SERIAL_DEV_BUS_ABSTRACTIONS
+ bool "Rust Serial device bus abstractions"
+ depends on RUST
+ select SERIAL_DEV_BUS
+ help
+ This enables the Rust abstraction for the serial device bus API.
+
if SERIAL_DEV_BUS
config SERIAL_DEV_CTRL_TTYPORT
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 1124785e210b..fe7c505da236 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -85,6 +85,7 @@
#include <linux/regulator/consumer.h>
#include <linux/sched.h>
#include <linux/security.h>
+#include <linux/serdev.h>
#include <linux/slab.h>
#include <linux/sys_soc.h>
#include <linux/task_work.h>
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 998e31052e66..6921a5ecb78a 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -87,6 +87,7 @@
#include "regulator.c"
#include "scatterlist.c"
#include "security.c"
+#include "serdev.c"
#include "signal.c"
#include "slab.c"
#include "spinlock.c"
diff --git a/rust/helpers/serdev.c b/rust/helpers/serdev.c
new file mode 100644
index 000000000000..c52b78ca3fc7
--- /dev/null
+++ b/rust/helpers/serdev.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/serdev.h>
+
+__rust_helper
+void rust_helper_serdev_device_driver_unregister(struct serdev_device_driver *sdrv)
+{
+ serdev_device_driver_unregister(sdrv);
+}
+
+__rust_helper
+void rust_helper_serdev_device_put(struct serdev_device *serdev)
+{
+ serdev_device_put(serdev);
+}
+
+__rust_helper
+void rust_helper_serdev_device_set_client_ops(struct serdev_device *serdev,
+ const struct serdev_device_ops *ops)
+{
+ serdev_device_set_client_ops(serdev, ops);
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 9512af7156df..d5ca17336739 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -119,6 +119,8 @@
pub mod scatterlist;
pub mod security;
pub mod seq_file;
+#[cfg(CONFIG_RUST_SERIAL_DEV_BUS_ABSTRACTIONS)]
+pub mod serdev;
pub mod sizes;
#[cfg(CONFIG_SOC_BUS)]
pub mod soc;
diff --git a/rust/kernel/serdev.rs b/rust/kernel/serdev.rs
new file mode 100644
index 000000000000..ab5d6446b091
--- /dev/null
+++ b/rust/kernel/serdev.rs
@@ -0,0 +1,590 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Abstractions for the serial device bus.
+//!
+//! C header: [`include/linux/serdev.h`](srctree/include/linux/serdev.h)
+
+use crate::{
+ acpi,
+ device,
+ driver,
+ error::{
+ from_result,
+ to_result,
+ VTABLE_DEFAULT_ERROR, //
+ },
+ new_mutex,
+ of,
+ prelude::*,
+ sync::{
+ aref::AlwaysRefCounted,
+ Mutex, //
+ },
+ time::{
+ msecs_to_jiffies,
+ Jiffies,
+ Msecs, //
+ },
+ types::{
+ Opaque,
+ ScopeGuard, //
+ }, //
+};
+
+use core::{
+ cell::UnsafeCell,
+ marker::PhantomData,
+ mem::{offset_of, MaybeUninit},
+ num::NonZero,
+ ptr::NonNull, //
+};
+
+/// Parity bit to use with a serial device.
+#[repr(u32)]
+pub enum Parity {
+ /// No parity bit.
+ None = bindings::serdev_parity_SERDEV_PARITY_NONE,
+ /// Even partiy.
+ Even = bindings::serdev_parity_SERDEV_PARITY_EVEN,
+ /// Odd parity.
+ Odd = bindings::serdev_parity_SERDEV_PARITY_ODD,
+}
+
+/// Timeout in Jiffies.
+pub enum Timeout {
+ /// Wait for a specific amount of [`Jiffies`].
+ Jiffies(NonZero<Jiffies>),
+ /// Wait for a specific amount of [`Msecs`].
+ Milliseconds(NonZero<Msecs>),
+ /// Wait as long as possible.
+ ///
+ /// This is equivalent to [`kernel::task::MAX_SCHEDULE_TIMEOUT`].
+ Max,
+}
+
+impl Timeout {
+ fn into_jiffies(self) -> isize {
+ match self {
+ Self::Jiffies(value) => value.get().try_into().unwrap_or_default(),
+ Self::Milliseconds(value) => {
+ msecs_to_jiffies(value.get()).try_into().unwrap_or_default()
+ }
+ Self::Max => 0,
+ }
+ }
+}
+
+/// An adapter for the registration of serial device bus device drivers.
+pub struct Adapter<T: Driver>(T);
+
+// SAFETY:
+// - `bindings::serdev_device_driver` is a C type declared as `repr(C)`.
+// - `PrivateData<'bound, T>` is the type of the driver's device private data.
+// - `struct serdev_device_driver` embeds a `struct device_driver`.
+// - `DEVICE_DRIVER_OFFSET` is the correct byte offset to the embedded `struct device_driver`.
+unsafe impl<T: Driver> driver::DriverLayout for Adapter<T> {
+ type DriverType = bindings::serdev_device_driver;
+ type DriverData<'bound> = PrivateData<'bound, T>;
+ const DEVICE_DRIVER_OFFSET: usize = core::mem::offset_of!(Self::DriverType, driver);
+}
+
+// SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if
+// a preceding call to `register` has been successful.
+unsafe impl<T: Driver> driver::RegistrationOps for Adapter<T> {
+ unsafe fn register(
+ sdrv: &Opaque<Self::DriverType>,
+ name: &'static CStr,
+ module: &'static ThisModule,
+ ) -> Result {
+ let of_table = match T::OF_ID_TABLE {
+ Some(table) => table.as_ptr(),
+ None => core::ptr::null(),
+ };
+
+ let acpi_table = match T::ACPI_ID_TABLE {
+ Some(table) => table.as_ptr(),
+ None => core::ptr::null(),
+ };
+
+ // SAFETY: It's safe to set the fields of `struct serdev_device_driver` on initialization.
+ unsafe {
+ (*sdrv.get()).driver.name = name.as_char_ptr();
+ (*sdrv.get()).probe = Some(Self::probe_callback);
+ (*sdrv.get()).remove = Some(Self::remove_callback);
+ (*sdrv.get()).driver.of_match_table = of_table;
+ (*sdrv.get()).driver.acpi_match_table = acpi_table;
+ }
+
+ // SAFETY: `sdrv` is guaranteed to be a valid `DriverType`.
+ to_result(unsafe { bindings::__serdev_device_driver_register(sdrv.get(), module.0) })
+ }
+
+ unsafe fn unregister(sdrv: &Opaque<Self::DriverType>) {
+ // SAFETY: `sdrv` is guaranteed to be a valid `DriverType`.
+ unsafe { bindings::serdev_device_driver_unregister(sdrv.get()) };
+ }
+}
+
+#[doc(hidden)]
+#[pin_data(PinnedDrop)]
+pub struct PrivateData<'bound, T: Driver> {
+ sdev: &'bound Device<device::Bound>,
+ #[pin]
+ driver: UnsafeCell<MaybeUninit<T::Data<'bound>>>,
+ open: UnsafeCell<bool>,
+ #[pin]
+ active: Mutex<bool>,
+}
+
+#[pinned_drop]
+impl<T: Driver> PinnedDrop for PrivateData<'_, T> {
+ fn drop(self: Pin<&mut Self>) {
+ let mut active = self.active.lock();
+ if *active {
+ // SAFETY:
+ // - We have exclusive access to `self.driver`.
+ // - `self.driver` is guaranteed to be initialized.
+ unsafe { (*self.driver.get()).assume_init_drop() };
+ *active = false;
+ }
+
+ // SAFETY: We have exclusive access to `self.open`.
+ if unsafe { *self.open.get() } {
+ // SAFETY: `self.sdev.as_raw()` is guaranteed to be a pointer to a valid
+ // `struct serdev_device`.
+ unsafe { bindings::serdev_device_close(self.sdev.as_raw()) };
+ }
+ }
+}
+
+impl<T: Driver> Adapter<T> {
+ const OPS: &'static bindings::serdev_device_ops = &bindings::serdev_device_ops {
+ receive_buf: if T::HAS_RECEIVE {
+ Some(Self::receive_buf_callback)
+ } else {
+ None
+ },
+ write_wakeup: Some(bindings::serdev_device_write_wakeup),
+ };
+
+ extern "C" fn probe_callback(sdev: *mut bindings::serdev_device) -> kernel::ffi::c_int {
+ // SAFETY: The serial device bus only ever calls the probe callback with a valid pointer to
+ // a `struct serdev_device`.
+ //
+ // INVARIANT: `sdev` is valid for the duration of `probe_callback()`.
+ let sdev = unsafe { &*sdev.cast::<Device<device::CoreInternal<'_>>>() };
+ let info = <Self as driver::Adapter>::id_info(sdev.as_ref());
+
+ from_result(|| {
+ sdev.as_ref().set_drvdata(try_pin_init!(PrivateData::<T> {
+ sdev: &**sdev,
+ driver: MaybeUninit::<T::Data<'_>>::zeroed().into(),
+ open: false.into(),
+ active <- new_mutex!(false),
+ }))?;
+ // SAFETY: We just set drvdata to `PrivateData<'_, T>`.
+ let private_data = unsafe { sdev.as_ref().drvdata_borrow::<PrivateData<'_, T>>() };
+ let private_data = ScopeGuard::new_with_data(private_data, |_| {
+ // SAFETY: We just set drvdata to `PrivateData<'_, T>`.
+ drop(unsafe { sdev.as_ref().drvdata_obtain::<PrivateData<'_, T>>() });
+ });
+ let mut active = private_data.active.lock();
+
+ // SAFETY: `sdev.as_raw()` is guaranteed to be a valid pointer to `serdev_device`.
+ unsafe { bindings::serdev_device_set_client_ops(sdev.as_raw(), Self::OPS) };
+
+ // SAFETY: The serial device bus only ever calls the probe callback with a valid pointer
+ // to a `serdev_device`.
+ to_result(unsafe { bindings::serdev_device_open(sdev.as_raw()) })?;
+
+ // SAFETY: We have exclusive access to `private_data.open`.
+ unsafe { *private_data.open.get() = true };
+
+ let data = T::probe(sdev, info);
+
+ // SAFETY: We have exclusive access to `private_data.driver`.
+ let driver = unsafe { &mut *private_data.driver.get() };
+ // SAFETY:
+ // - `driver.as_mut_ptr()` is a valid pointer to uninitialized data.
+ // - `private_data.driver` is pinned.
+ let result = unsafe { data.__pinned_init(driver.as_mut_ptr()) };
+
+ *active = result.is_ok();
+
+ drop(active);
+
+ result.map(|()| {
+ private_data.dismiss();
+ 0
+ })
+ })
+ }
+
+ extern "C" fn remove_callback(sdev: *mut bindings::serdev_device) {
+ // SAFETY: The serial device bus only ever calls the remove callback with a valid pointer
+ // to a `struct serdev_device`.
+ //
+ // INVARIANT: `sdev` is valid for the duration of `remove_callback()`.
+ let sdev = unsafe { &*sdev.cast::<Device<device::CoreInternal<'_>>>() };
+
+ // SAFETY: `remove_callback` is only ever called after a successful call to
+ // `probe_callback`, hence it's guaranteed that `Device::set_drvdata()` has been called
+ // and stored a `Pin<KBox<PrivateData<'_, T>>>`.
+ let private_data = unsafe { sdev.as_ref().drvdata_borrow::<PrivateData<'_, T>>() };
+
+ // SAFETY: No one has exclusive access to `private_data.driver`.
+ let data = unsafe { &*private_data.driver.get() };
+ // SAFETY:
+ // - `private_data.driver` is pinned.
+ // - `remove_callback` is only ever called after a successful call to `probe_callback`,
+ // hence it's guaranteed that `private_data.driver` was initialized.
+ let data_pinned = unsafe { Pin::new_unchecked(data.assume_init_ref()) };
+
+ T::unbind(sdev, data_pinned);
+ }
+
+ extern "C" fn receive_buf_callback(
+ sdev: *mut bindings::serdev_device,
+ buf: *const u8,
+ length: usize,
+ ) -> usize {
+ // SAFETY: The serial device bus only ever calls the receive buf callback with a valid
+ // pointer to a `struct serdev_device`.
+ //
+ // INVARIANT: `sdev` is valid for the duration of `receive_buf_callback()`.
+ let sdev = unsafe { &*sdev.cast::<Device<device::BoundInternal>>() };
+
+ // SAFETY: `receive_buf_callback` is only ever called after a successful call to
+ // `probe_callback`, hence it's guaranteed that `Device::set_drvdata()` has been called
+ // and stored a `Pin<KBox<PrivateData<'_, T>>>`.
+ let private_data = unsafe { sdev.as_ref().drvdata_borrow::<PrivateData<'_, T>>() };
+ let active = private_data.active.lock();
+
+ if !*active {
+ return length;
+ }
+
+ // SAFETY: No one has exclusive access to `private_data.driver`.
+ let data = unsafe { &*private_data.driver.get() };
+ // SAFETY:
+ // - `private_data.driver` is pinned.
+ // - `receive_buf_callback` is only ever called after a successful call to `probe_callback`,
+ // hence it's guaranteed that `private_data.driver` was initialized.
+ let data_pinned = unsafe { Pin::new_unchecked(data.assume_init_ref()) };
+
+ // SAFETY: `buf` is guaranteed to be non-null and has the size of `length`.
+ let buf = unsafe { core::slice::from_raw_parts(buf, length) };
+
+ T::receive(sdev, data_pinned, buf)
+ }
+}
+
+impl<T: Driver> driver::Adapter for Adapter<T> {
+ type IdInfo = T::IdInfo;
+
+ fn of_id_table() -> Option<of::IdTable<Self::IdInfo>> {
+ T::OF_ID_TABLE
+ }
+
+ fn acpi_id_table() -> Option<acpi::IdTable<Self::IdInfo>> {
+ T::ACPI_ID_TABLE
+ }
+}
+
+/// Declares a kernel module that exposes a single serial device bus device driver.
+///
+/// # Examples
+///
+/// ```ignore
+/// kernel::module_serdev_device_driver! {
+/// type: MyDriver,
+/// name: "Module name",
+/// authors: ["Author name"],
+/// description: "Description",
+/// license: "GPL v2",
+/// }
+/// ```
+#[macro_export]
+macro_rules! module_serdev_device_driver {
+ ($($f:tt)*) => {
+ $crate::module_driver!(<T>, $crate::serdev::Adapter<T>, { $($f)* });
+ };
+}
+
+/// The serial device bus device driver trait.
+///
+/// Drivers must implement this trait in order to get a serial device bus device driver registered.
+///
+/// # Examples
+///
+///```
+/// # use kernel::{
+/// acpi,
+/// bindings,
+/// device::{
+/// Bound,
+/// Core, //
+/// },
+/// of,
+/// serdev, //
+/// };
+///
+/// struct MyDriver;
+///
+/// kernel::of_device_table!(
+/// OF_TABLE,
+/// MODULE_OF_TABLE,
+/// <MyDriver as serdev::Driver>::IdInfo,
+/// [
+/// (of::DeviceId::new(c"test,device"), ())
+/// ]
+/// );
+///
+/// kernel::acpi_device_table!(
+/// ACPI_TABLE,
+/// MODULE_ACPI_TABLE,
+/// <MyDriver as serdev::Driver>::IdInfo,
+/// [
+/// (acpi::DeviceId::new(c"LNUXBEEF"), ())
+/// ]
+/// );
+///
+/// #[vtable]
+/// impl serdev::Driver for MyDriver {
+/// type IdInfo = ();
+/// type Data<'bound> = Self;
+/// const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+/// const ACPI_ID_TABLE: Option<acpi::IdTable<Self::IdInfo>> = Some(&ACPI_TABLE);
+///
+/// fn probe<'bound>(
+/// sdev: &'bound serdev::Device<Core<'_>>,
+/// _id_info: Option<&'bound Self::IdInfo>,
+/// ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound {
+/// sdev.set_baudrate(115200);
+/// sdev.write_all(b"Hello\n", serdev::Timeout::Max)?;
+/// Ok(MyDriver)
+/// }
+/// }
+///```
+#[vtable]
+pub trait Driver {
+ /// The type holding driver private data about each device id supported by the driver.
+ // TODO: Use associated_type_defaults once stabilized:
+ //
+ // ```
+ // type IdInfo: 'static = ();
+ // ```
+ type IdInfo: 'static;
+
+ /// The type of the driver's bus device private data.
+ type Data<'bound>: Send + 'bound;
+
+ /// The table of OF device ids supported by the driver.
+ const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = None;
+
+ /// The table of ACPI device ids supported by the driver.
+ const ACPI_ID_TABLE: Option<acpi::IdTable<Self::IdInfo>> = None;
+
+ /// Serial device bus device driver probe.
+ ///
+ /// Called when a new serial device bus device is added or discovered.
+ /// Implementers should attempt to initialize the device here.
+ fn probe<'bound>(
+ sdev: &'bound Device<device::Core<'_>>,
+ id_info: Option<&'bound Self::IdInfo>,
+ ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound;
+
+ /// Serial device bus device driver unbind.
+ ///
+ /// Called when a [`Device`] is unbound from its bound [`Driver`]. Implementing this callback
+ /// is optional.
+ ///
+ /// This callback serves as a place for drivers to perform teardown operations that require a
+ /// `&Device<Core>` or `&Device<Bound>` reference. For instance.
+ ///
+ /// Otherwise, release operations for driver resources should be performed in `Drop`.
+ fn unbind<'bound>(sdev: &'bound Device<device::Core<'_>>, this: Pin<&Self::Data<'bound>>) {
+ let _ = (sdev, this);
+ }
+
+ /// Serial device bus device data receive callback.
+ ///
+ /// Called when data got received from device.
+ ///
+ /// Returns the number of bytes accepted.
+ fn receive<'bound>(
+ sdev: &'bound Device<device::Bound>,
+ this: Pin<&Self::Data<'bound>>,
+ data: &[u8],
+ ) -> usize {
+ let _ = (sdev, this, data);
+ build_error!(VTABLE_DEFAULT_ERROR)
+ }
+}
+
+/// The serial device bus device representation.
+///
+/// This structure represents the Rust abstraction for a C `struct serdev_device`. The
+/// implementation abstracts the usage of an already existing C `struct serdev_device` within Rust
+/// code that we get passed from the C side.
+///
+/// # Invariants
+///
+/// A [`Device`] instance represents a valid `struct serdev_device` created by the C portion of
+/// the kernel.
+#[repr(transparent)]
+pub struct Device<Ctx: device::DeviceContext = device::Normal>(
+ Opaque<bindings::serdev_device>,
+ PhantomData<Ctx>,
+);
+
+impl<Ctx: device::DeviceContext> Device<Ctx> {
+ fn as_raw(&self) -> *mut bindings::serdev_device {
+ self.0.get()
+ }
+}
+
+impl Device<device::Bound> {
+ /// Set the baudrate in bits per second.
+ ///
+ /// Common baudrates are 115200, 9600, 19200, 57600, 4800.
+ ///
+ /// Use [`Device::write_flush`] before calling this if you have written data prior to this call.
+ pub fn set_baudrate(&self, speed: u32) -> Result<(), u32> {
+ // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `serdev_device`.
+ let ret = unsafe { bindings::serdev_device_set_baudrate(self.as_raw(), speed) };
+ if ret == speed {
+ Ok(())
+ } else {
+ Err(ret)
+ }
+ }
+
+ /// Set if flow control should be enabled.
+ ///
+ /// Use [`Device::write_flush`] before calling this if you have written data prior to this call.
+ pub fn set_flow_control(&self, enable: bool) {
+ // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `serdev_device`.
+ unsafe { bindings::serdev_device_set_flow_control(self.as_raw(), enable) };
+ }
+
+ /// Set parity to use.
+ ///
+ /// Use [`Device::write_flush`] before calling this if you have written data prior to this call.
+ pub fn set_parity(&self, parity: Parity) -> Result {
+ // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `serdev_device`.
+ to_result(unsafe { bindings::serdev_device_set_parity(self.as_raw(), parity as u32) })
+ }
+
+ /// Write data to the serial device until the controller has accepted all the data or has
+ /// been interrupted by a timeout or signal.
+ ///
+ /// Note that any accepted data has only been buffered by the controller. Use
+ /// [`Device::wait_until_sent`] to make sure the controller write buffer has actually been
+ /// emptied.
+ ///
+ /// Returns the number of bytes written (less than `data.len()` if interrupted).
+ /// [`kernel::error::code::ETIMEDOUT`] or [`kernel::error::code::ERESTARTSYS`] if interrupted
+ /// before any bytes were written.
+ pub fn write_all(&self, data: &[u8], timeout: Timeout) -> Result<usize> {
+ // SAFETY:
+ // - `self.as_raw()` is guaranteed to be a pointer to a valid `serdev_device`.
+ // - `data.as_ptr()` is guaranteed to be a valid array pointer with the size of
+ // `data.len()`.
+ let ret = unsafe {
+ bindings::serdev_device_write(
+ self.as_raw(),
+ data.as_ptr(),
+ data.len(),
+ timeout.into_jiffies(),
+ )
+ };
+ // CAST: negative return values are guaranteed to be between `-MAX_ERRNO` and `-1`,
+ // which always fit into a `i32`.
+ to_result(ret as i32).map(|()| ret.unsigned_abs())
+ }
+
+ /// Write data to the serial device.
+ ///
+ /// If you want to write until the controller has accepted all the data, use
+ /// [`Device::write_all`].
+ ///
+ /// Note that any accepted data has only been buffered by the controller. Use
+ /// [ Device::wait_until_sent`] to make sure the controller write buffer has actually been
+ /// emptied.
+ ///
+ /// Returns the number of bytes written (less than `data.len()` if not enough room in the
+ /// write buffer).
+ pub fn write(&self, data: &[u8]) -> Result<u32> {
+ // SAFETY:
+ // - `self.as_raw()` is guaranteed to be a pointer to a valid `serdev_device`.
+ // - `data.as_ptr()` is guaranteed to be a valid array pointer with the size of
+ // `data.len()`.
+ let ret =
+ unsafe { bindings::serdev_device_write_buf(self.as_raw(), data.as_ptr(), data.len()) };
+
+ to_result(ret as i32).map(|()| ret.unsigned_abs())
+ }
+
+ /// Send data to the serial device immediately.
+ ///
+ /// Note that this doesn't guarantee that the data has been transmitted.
+ /// Use [`Device::wait_until_sent`] for this purpose.
+ pub fn write_flush(&self) {
+ // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `serdev_device`.
+ unsafe { bindings::serdev_device_write_flush(self.as_raw()) };
+ }
+
+ /// Wait for the data to be sent.
+ ///
+ /// After this function, the write buffer of the controller should be empty.
+ pub fn wait_until_sent(&self, timeout: Timeout) {
+ // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `serdev_device`.
+ unsafe { bindings::serdev_device_wait_until_sent(self.as_raw(), timeout.into_jiffies()) };
+ }
+}
+
+// SAFETY: `serdev::Device` is a transparent wrapper of `struct serdev_device`.
+// The offset is guaranteed to point to a valid device field inside `serdev::Device`.
+unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx> {
+ const OFFSET: usize = offset_of!(bindings::serdev_device, dev);
+}
+
+// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
+// argument.
+kernel::impl_device_context_deref!(unsafe { Device });
+kernel::impl_device_context_into_aref!(Device);
+
+// SAFETY: Instances of `Device` are always reference-counted.
+unsafe impl AlwaysRefCounted for Device {
+ fn inc_ref(&self) {
+ self.as_ref().inc_ref();
+ }
+
+ unsafe fn dec_ref(obj: NonNull<Self>) {
+ // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+ unsafe { bindings::serdev_device_put(obj.cast().as_ptr()) }
+ }
+}
+
+impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
+ fn as_ref(&self) -> &device::Device<Ctx> {
+ // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
+ // `struct serdev_device`.
+ let dev = unsafe { &raw mut (*self.as_raw()).dev };
+
+ // SAFETY: `dev` points to a valid `struct device`.
+ unsafe { device::Device::from_raw(dev) }
+ }
+}
+
+// SAFETY: A `Device` is always reference-counted and can be released from any thread.
+unsafe impl Send for Device {}
+
+// SAFETY: `Device` can be shared among threads because all methods of `Device`
+// (i.e. `Device<Normal>) are thread safe.
+unsafe impl Sync for Device {}
+
+// SAFETY: Same as `Device<Normal>` -- the underlying `struct serdev_device` is the same;
+// `Bound` is a zero-sized type-state marker that does not affect thread safety.
+unsafe impl Sync for Device<device::Bound> {}
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v13 2/3] samples: rust: add Rust serial device bus sample device driver
2026-07-12 16:58 [PATCH v13 0/3] rust: add basic serial device bus abstractions Markus Probst
2026-07-12 16:58 ` [PATCH v13 1/3] " Markus Probst
@ 2026-07-12 16:58 ` Markus Probst
2026-07-12 17:19 ` sashiko-bot
2026-07-12 16:58 ` [PATCH v13 3/3] MAINTAINERS: serdev: Add self for serdev Markus Probst
2 siblings, 1 reply; 6+ messages in thread
From: Markus Probst @ 2026-07-12 16:58 UTC (permalink / raw)
To: Rob Herring, Greg Kroah-Hartman, Jiri Slaby, Miguel Ojeda,
Gary Guo, Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Kari Argillander,
Rafael J. Wysocki, Viresh Kumar, Boqun Feng, David Airlie,
Simona Vetter, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, Boqun Feng
Cc: linux-serial, linux-kernel, rust-for-linux, linux-pm, driver-core,
dri-devel, Markus Probst
Add a sample Rust serial device bus device driver illustrating the usage
of the serial device bus abstractions.
This drivers probes through either a match of device / driver name or a
match within the OF ID table.
Signed-off-by: Markus Probst <markus.probst@posteo.de>
---
MAINTAINERS | 1 +
samples/rust/Kconfig | 11 +++++
samples/rust/Makefile | 1 +
samples/rust/rust_driver_serdev.rs | 91 ++++++++++++++++++++++++++++++++++++++
4 files changed, 104 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 00d977ce7028..ed4f8f2f17d5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -24569,6 +24569,7 @@ F: drivers/tty/serdev/
F: include/linux/serdev.h
F: rust/helpers/serdev.c
F: rust/kernel/serdev.rs
+F: samples/rust/rust_driver_serdev.rs
SERIAL IR RECEIVER
M: Sean Young <sean@mess.org>
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index c49ab9106345..31d62533ef25 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -161,6 +161,17 @@ config SAMPLE_RUST_DRIVER_AUXILIARY
If unsure, say N.
+config SAMPLE_RUST_DRIVER_SERDEV
+ tristate "Serial Device Bus Device Driver"
+ select RUST_SERIAL_DEV_BUS_ABSTRACTIONS
+ help
+ This option builds the Rust serial device bus driver sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_driver_serdev.
+
+ If unsure, say N.
+
config SAMPLE_RUST_SOC
tristate "SoC Driver"
select SOC_BUS
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index 6c0aaa58cccc..b986b681cde5 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-$(CONFIG_SAMPLE_RUST_DRIVER_SERDEV) += rust_driver_serdev.o
obj-$(CONFIG_SAMPLE_RUST_CONFIGFS) += rust_configfs.o
obj-$(CONFIG_SAMPLE_RUST_SOC) += rust_soc.o
diff --git a/samples/rust/rust_driver_serdev.rs b/samples/rust/rust_driver_serdev.rs
new file mode 100644
index 000000000000..824affbf6593
--- /dev/null
+++ b/samples/rust/rust_driver_serdev.rs
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust Serial device bus device driver sample.
+
+use kernel::{
+ acpi,
+ device::{
+ Bound,
+ Core, //
+ },
+ of,
+ prelude::*,
+ serdev,
+ sync::aref::ARef, //
+};
+
+struct SampleDriver {
+ sdev: ARef<serdev::Device>,
+}
+
+kernel::of_device_table!(
+ OF_TABLE,
+ MODULE_OF_TABLE,
+ <SampleDriver as serdev::Driver>::IdInfo,
+ [(of::DeviceId::new(c"test,rust_driver_serdev"), ())]
+);
+
+kernel::acpi_device_table!(
+ ACPI_TABLE,
+ MODULE_ACPI_TABLE,
+ <SampleDriver as serdev::Driver>::IdInfo,
+ [(acpi::DeviceId::new(c"LNUXBEEF"), ())]
+);
+
+#[vtable]
+impl serdev::Driver for SampleDriver {
+ type IdInfo = ();
+ type Data<'bound> = Self;
+ const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+ const ACPI_ID_TABLE: Option<acpi::IdTable<Self::IdInfo>> = Some(&ACPI_TABLE);
+
+ fn probe<'bound>(
+ sdev: &'bound serdev::Device<Core<'_>>,
+ _info: Option<&'bound Self::IdInfo>,
+ ) -> impl PinInit<Self, Error> + 'bound {
+ let dev = sdev.as_ref();
+
+ dev_dbg!(dev, "Probe Rust Serial device bus device driver sample.\n");
+
+ if sdev
+ .set_baudrate(
+ dev.fwnode()
+ .and_then(|fwnode| fwnode.property_read(c"baudrate").optional())
+ .unwrap_or(115200),
+ )
+ .is_err()
+ {
+ return Err(EINVAL);
+ }
+ sdev.set_flow_control(false);
+ sdev.set_parity(serdev::Parity::None)?;
+
+ Ok(Self { sdev: sdev.into() })
+ }
+
+ fn receive<'bound>(
+ sdev: &'bound serdev::Device<Bound>,
+ _this: Pin<&Self>,
+ data: &[u8],
+ ) -> usize {
+ let _ = sdev.write_all(data, serdev::Timeout::Max);
+ data.len()
+ }
+}
+
+impl Drop for SampleDriver {
+ fn drop(&mut self) {
+ dev_dbg!(
+ self.sdev.as_ref(),
+ "Remove Rust Serial device bus device driver sample.\n"
+ );
+ }
+}
+
+kernel::module_serdev_device_driver! {
+ type: SampleDriver,
+ name: "rust_driver_serdev",
+ authors: ["Markus Probst"],
+ description: "Rust Serial device bus device driver",
+ license: "GPL v2",
+}
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread