* [PATCH v8 2/3] rust: spi: add SPI driver abstractions
[not found] ` <20261114010745.82389-1-847807867@qq.com>
@ 2026-11-14 1:07 ` Shuai Liu
2026-11-14 1:07 ` [PATCH v8 3/3] samples: rust: add SPI driver sample Shuai Liu
1 sibling, 0 replies; 4+ messages in thread
From: Shuai Liu @ 2026-11-14 1:07 UTC (permalink / raw)
To: linux-spi
Cc: rust-for-linux, Mark Brown, ojeda, dakr, linux-kernel, 847807867
Add the Rust abstractions for the SPI driver subsystem, allowing SPI
drivers to be written in Rust.
This adds the following abstractions:
- `spi::DeviceId`: a driver-side device id.
- `spi::Adapter`: the registration of SPI drivers, implementing
`driver::DriverLayout` and `driver::RegistrationOps`.
- `spi::Driver`: the trait that SPI drivers implement, with `probe()`,
`shutdown()` and `unbind()` callbacks.
- `spi::SpiDevice`: a representation of `struct spi_device`, providing
device configuration accessors and device I/O on bound devices.
- `spi::Transfer`: a single SPI transfer that transmits, receives, or
does both simultaneously (full duplex).
- `module_spi_driver!` and `spi_device_table!` macros.
The module is only built when CONFIG_SPI is enabled, since the SPI core
functions it uses are not available otherwise.
The device configuration accessors and the I/O operations are only
available on `SpiDevice<Bound>`: an `ARef<SpiDevice>` may outlive the
driver's unbind and the device's or controller's unregistration, and the
SPI core's transfer path does not check the registration state, so
performing I/O on an unbound device is not sound. Moreover, once the
device is unbound, another driver may bind to the same
`struct spi_device` and mutate the device configuration with plain,
non-atomic writes (e.g. via `spi_setup()`), so reading the configuration
would be a data race. Driver callbacks receive a `SpiDevice<Core>`,
which dereferences to `SpiDevice<Bound>`.
Device I/O is built on a single primitive, `SpiDevice::transfer()`,
which maps to the C `spi_sync()` API: a sequence of `Transfer`s is
submitted as one `spi_message`, executed in order with the chip select
asserted for the whole message. The convenience methods `write()`,
`read()` and `write_then_read()` are thin wrappers on top of it.
`spi_sync()` requires transfer buffers to be DMA-safe, and Rust slices
may be located anywhere (e.g. on the stack), so `transfer()` copies all
data into DMA-safe bounce buffers before submitting the message and
copies received data back afterwards. Unlike the previous approach of
leveraging the C convenience wrappers, this maps directly onto the
lower-level C APIs and also supports full-duplex transfers, which the C
convenience wrappers do not offer.
Match data lookup follows the same order as the C core's
spi_get_device_match_data(): first the OF/ACPI match data, then the SPI
id table. Entries without driver data (e.g. `@none` id tables) are
handled gracefully.
Signed-off-by: Shuai Liu <847807867@qq.com>
Link: https://lore.kernel.org/rust-for-linux/179451185979.339049.12323339081307899766.b4-review@b4/
---
rust/kernel/Kconfig.test | 11 +
rust/kernel/lib.rs | 2 +
rust/kernel/spi.rs | 673 +++++++++++++++++++++++++++++++++++++++
3 files changed, 686 insertions(+)
create mode 100644 rust/kernel/spi.rs
diff --git a/rust/kernel/Kconfig.test b/rust/kernel/Kconfig.test
index d198ea0d136c9..0bcc653bb821b 100644
--- a/rust/kernel/Kconfig.test
+++ b/rust/kernel/Kconfig.test
@@ -105,6 +105,17 @@ config RUST_BUG_KUNIT_TEST
If unsure, say N.
+config RUST_SPI_KUNIT_TEST
+ bool "KUnit tests for the Rust SPI driver abstractions" if !KUNIT_ALL_TESTS
+ depends on SPI=y
+ default KUNIT_ALL_TESTS
+ help
+ This option enables KUnit tests for the Rust SPI driver
+ abstractions. These are only for development and testing, not
+ for regular kernel use cases.
+
+ If unsure, say N.
+
config RUST_TIME_KUNIT_TEST
bool "KUnit tests for the Rust time API" if !KUNIT_ALL_TESTS
default KUNIT_ALL_TESTS
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 0d5e9f5fd3cb2..a169445b41403 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -139,6 +139,8 @@
pub mod sizes;
#[cfg(CONFIG_SOC_BUS)]
pub mod soc;
+#[cfg(CONFIG_SPI)]
+pub mod spi;
#[doc(hidden)]
pub mod std_vendor;
pub mod str;
diff --git a/rust/kernel/spi.rs b/rust/kernel/spi.rs
new file mode 100644
index 0000000000000..424563baddb3e
--- /dev/null
+++ b/rust/kernel/spi.rs
@@ -0,0 +1,673 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! SPI Driver subsystem
+//!
+//! This module adds abstractions for the SPI driver subsystem, allowing drivers to be
+//! written in Rust for SPI devices.
+
+// SPI Driver abstractions.
+use crate::{
+ acpi,
+ device,
+ device_id::{
+ RawDeviceId,
+ RawDeviceIdIndex, //
+ },
+ driver,
+ error::*,
+ of,
+ prelude::*,
+ sync::aref::AlwaysRefCounted,
+ types::Opaque, //
+};
+
+use core::{
+ marker::PhantomData,
+ mem::offset_of,
+ ptr::NonNull, //
+};
+
+/// An SPI device id table.
+#[repr(transparent)]
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::spi_device_id);
+
+impl DeviceId {
+ const SPI_NAME_SIZE: usize = 32;
+
+ /// Create a new device id from an SPI 'id' string.
+ #[inline(always)]
+ pub const fn new(id: &'static CStr) -> Self {
+ let src = id.to_bytes_with_nul();
+ build_assert!(src.len() <= Self::SPI_NAME_SIZE, "ID exceeds 32 bytes");
+ let mut spi: bindings::spi_device_id = pin_init::zeroed();
+ let mut i = 0;
+ while i < src.len() {
+ spi.name[i] = src[i];
+ i += 1;
+ }
+
+ Self(spi)
+ }
+}
+
+// SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `spi_device_id` and does not add
+// additional invariants, so it's safe to transmute to `RawType`.
+unsafe impl RawDeviceId for DeviceId {
+ type RawType = bindings::spi_device_id;
+}
+
+// SAFETY: `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
+unsafe impl RawDeviceIdIndex for DeviceId {
+ const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::spi_device_id, driver_data);
+}
+
+/// IdTable type for SPI
+pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
+
+/// Create a SPI `IdTable` with its alias for modpost.
+#[macro_export]
+macro_rules! spi_device_table {
+ ($($tt:tt)*) => {
+ $crate::module_device_table!("spi", $crate::spi::DeviceId, $($tt)*);
+ };
+}
+
+/// An adapter for the registration of SPI drivers.
+pub struct Adapter<T: Driver>(T);
+
+// SAFETY:
+// - `bindings::spi_driver` is a C type declared as `repr(C)`.
+// - `T::Data` is the type of the driver's device private data.
+// - `struct spi_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::spi_driver;
+ type DriverData<'bound> = T::Data<'bound>;
+ 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 {
+ build_assert!(
+ T::ACPI_ID_TABLE.is_some() || T::OF_ID_TABLE.is_some() || T::SPI_ID_TABLE.is_some(),
+ "At least one of ACPI/OF/Legacy tables must be present when registering an spi driver"
+ );
+
+ let spi_table = match T::SPI_ID_TABLE {
+ Some(table) => table.as_ptr(),
+ None => core::ptr::null(),
+ };
+
+ 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 spi_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()).shutdown = Some(Self::shutdown_callback);
+ (*sdrv.get()).id_table = spi_table;
+ (*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::__spi_register_driver(module.as_ptr(), sdrv.get()) })
+ }
+
+ unsafe fn unregister(sdrv: &Opaque<Self::DriverType>) {
+ // SAFETY: `sdrv` is guaranteed to be a valid `DriverType`.
+ unsafe { bindings::spi_unregister_driver(sdrv.get()) }
+ }
+}
+
+impl<T: Driver> Adapter<T> {
+ extern "C" fn probe_callback(sdev: *mut bindings::spi_device) -> kernel::ffi::c_int {
+ // SAFETY: The SPI bus only ever calls the probe callback with a valid pointer to a
+ // `struct spi_device`.
+ //
+ // INVARIANT: `sdev` is valid for the duration of `probe_callback()`.
+ let sdev = unsafe { &*sdev.cast::<SpiDevice<device::CoreInternal<'_>>>() };
+
+ // Match the lookup order of the C core's `spi_get_device_match_data()`: first the
+ // OF/ACPI match data, then the SPI id table.
+ //
+ // SAFETY: `sdev` matched data is of type `Self::IdInfo`.
+ let info = unsafe { <Self as driver::Adapter>::id_info(sdev.as_ref()) }
+ .or_else(|| Self::spi_id_info(sdev));
+
+ from_result(|| {
+ let data = T::probe(sdev, info);
+
+ sdev.as_ref().set_drvdata(data)?;
+ Ok(0)
+ })
+ }
+
+ extern "C" fn remove_callback(sdev: *mut bindings::spi_device) {
+ // SAFETY: `sdev` is a valid pointer to a `struct spi_device`.
+ let sdev = unsafe { &*sdev.cast::<SpiDevice<device::CoreInternal<'_>>>() };
+
+ // SAFETY: `remove_callback` is only ever called after a successful call to
+ // `probe_callback`, hence it's guaranteed that `SpiDevice::set_drvdata()` has been called
+ // and stored a `Pin<KBox<T::Data<'_>>>`.
+ let data = unsafe { sdev.as_ref().drvdata_borrow::<T::Data<'_>>() };
+
+ T::unbind(sdev, data);
+ }
+
+ extern "C" fn shutdown_callback(sdev: *mut bindings::spi_device) {
+ // SAFETY: `shutdown_callback` is only ever called for a valid `sdev`
+ let sdev = unsafe { &*sdev.cast::<SpiDevice<device::CoreInternal<'_>>>() };
+
+ // SAFETY: `shutdown_callback` is only ever called after a successful call to
+ // `probe_callback`, hence it's guaranteed that `SpiDevice::set_drvdata()` has been called
+ // and stored a `Pin<KBox<T::Data<'_>>>`.
+ let data = unsafe { sdev.as_ref().drvdata_borrow::<T::Data<'_>>() };
+
+ T::shutdown(sdev, data);
+ }
+
+ /// Returns the driver's private data from the matching entry in the [`spi::IdTable`], if any.
+ ///
+ /// If this returns `None`, it means there is no match with an entry in the [`spi::IdTable`].
+ fn spi_id_info(dev: &SpiDevice) -> Option<&'static <Self as driver::Adapter>::IdInfo> {
+ // Ensure the driver has an SPI id table: the entries matched by `spi_get_device_id()`
+ // below come from the table registered in `register()`, i.e. `T::SPI_ID_TABLE`, which
+ // guarantees that every `driver_data` field is a valid `T::IdInfo`.
+ T::SPI_ID_TABLE.as_ref()?;
+
+ // SAFETY:
+ // - `dev` is guaranteed to be valid while it's alive, and so is `dev.as_raw()`.
+ //
+ // `spi_get_device_id()` looks up the registered driver id table using the device's
+ // modalias and returns either a pointer to a matching entry or `NULL`.
+ let raw_id = unsafe { bindings::spi_get_device_id(dev.as_raw()) };
+
+ if raw_id.is_null() {
+ return None;
+ }
+
+ // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of `struct spi_device_id` and
+ // does not add additional invariants, so it's safe to transmute.
+ let id = unsafe { &*raw_id.cast::<DeviceId>() };
+
+ // SAFETY: `id` comes from the driver's id table (as established by the `T::SPI_ID_TABLE`
+ // check above). By the safety requirements of `info_unchecked_opt()`, this is either a
+ // valid `T::IdInfo` or `NULL` (e.g. for a `@none` table), which `info_unchecked_opt()`
+ // handles by returning `None`.
+ unsafe { id.info_unchecked_opt::<T::IdInfo>() }
+ }
+}
+
+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 spi driver.
+///
+/// # Examples
+///
+/// ```ignore
+/// kernel::module_spi_driver! {
+/// type: MyDriver,
+/// name: "Module name",
+/// authors: ["Author name"],
+/// description: "Description",
+/// license: "GPL v2",
+/// }
+/// ```
+#[macro_export]
+macro_rules! module_spi_driver {
+ ($($f:tt)*) => {
+ $crate::module_driver!(<T>, $crate::spi::Adapter<T>, { $($f)* });
+ };
+}
+
+/// The spi driver trait.
+///
+/// Drivers must implement this trait in order to get a spi driver registered.
+///
+/// # Example
+///
+///```
+/// # use kernel::{device::Core, spi, of};
+///
+/// struct MyDriver;
+///
+/// kernel::spi_device_table!(
+/// SPI_TABLE,
+/// <MyDriver as spi::Driver>::IdInfo,
+/// [
+/// (spi::DeviceId::new(c"rust_driver_spi"), ())
+/// ]
+/// );
+///
+/// kernel::of_device_table!(
+/// OF_TABLE,
+/// <MyDriver as spi::Driver>::IdInfo,
+/// [
+/// (of::DeviceId::new(c"test,device"), ())
+/// ]
+/// );
+///
+/// impl spi::Driver for MyDriver {
+/// type IdInfo = ();
+/// type Data<'bound> = Self;
+/// const SPI_ID_TABLE: Option<spi::IdTable<Self::IdInfo>> = Some(&SPI_TABLE);
+/// const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+///
+/// fn probe<'bound>(
+/// _sdev: &'bound spi::SpiDevice<Core<'_>>,
+/// _id_info: Option<&'bound Self::IdInfo>,
+/// ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound {
+/// Err(ENODEV)
+/// }
+///
+/// fn shutdown<'bound>(
+/// _sdev: &'bound spi::SpiDevice<Core<'_>>,
+/// this: Pin<&Self::Data<'bound>>,
+/// ) {
+/// }
+/// }
+///```
+pub trait Driver {
+ /// The type holding information 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 device ids supported by the driver.
+ const SPI_ID_TABLE: Option<IdTable<Self::IdInfo>> = None;
+
+ /// 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;
+
+ /// SPI driver probe.
+ ///
+ /// Called when a new spi device is added or discovered.
+ /// Implementers should attempt to initialize the device here.
+ fn probe<'bound>(
+ dev: &'bound SpiDevice<device::Core<'_>>,
+ id_info: Option<&'bound Self::IdInfo>,
+ ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound;
+
+ /// SPI driver shutdown.
+ ///
+ /// Called by the kernel during system reboot or power-off to allow the [`Driver`] to bring the
+ /// [`SpiDevice`] into a safe state. Implementing this callback is optional.
+ ///
+ /// Typical actions include stopping transfers, disabling interrupts, or resetting the hardware
+ /// to prevent undesired behavior during shutdown.
+ ///
+ /// This callback is distinct from final resource cleanup, as the driver instance remains valid
+ /// after it returns. Any deallocation or teardown of driver-owned resources should instead be
+ /// handled in `Drop`.
+ fn shutdown<'bound>(dev: &'bound SpiDevice<device::Core<'_>>, this: Pin<&Self::Data<'bound>>) {
+ let _ = (dev, this);
+ }
+
+ /// SPI driver unbind.
+ ///
+ /// Called when the [`SpiDevice`] 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, drivers may try to perform I/O
+ /// operations to gracefully tear down the device.
+ ///
+ /// Otherwise, release operations for driver resources should be performed in `Drop`.
+ fn unbind<'bound>(dev: &'bound SpiDevice<device::Core<'_>>, this: Pin<&Self::Data<'bound>>) {
+ let _ = (dev, this);
+ }
+}
+
+/// The spi device representation.
+///
+/// This structure represents the Rust abstraction for a C `struct spi_device`. The
+/// implementation abstracts the usage of an existing C `struct spi_device` that
+/// gets passed from the C side.
+///
+/// # Invariants
+///
+/// A [`SpiDevice`] instance represents a valid `struct spi_device` created by the C portion of
+/// the kernel.
+#[repr(transparent)]
+pub struct SpiDevice<Ctx: device::DeviceContext = device::Normal>(
+ Opaque<bindings::spi_device>,
+ PhantomData<Ctx>,
+);
+
+impl<Ctx: device::DeviceContext> SpiDevice<Ctx> {
+ fn as_raw(&self) -> *mut bindings::spi_device {
+ self.0.get()
+ }
+}
+
+/// A single SPI transfer.
+///
+/// A transfer transmits, receives, or transmits and receives simultaneously (full duplex).
+/// A sequence of transfers is submitted to the device as a single message with
+/// [`SpiDevice::transfer`].
+///
+/// The buffers don't need to be DMA-safe: the data is copied into DMA-safe bounce buffers
+/// internally, since Rust slices may be located anywhere (e.g. on the stack).
+pub struct Transfer<'buf> {
+ tx: Option<&'buf [u8]>,
+ rx: Option<&'buf mut [u8]>,
+}
+
+impl<'buf> Transfer<'buf> {
+ /// Creates a transfer that transmits the data in `tx`.
+ pub fn write(tx: &'buf [u8]) -> Self {
+ Self {
+ tx: Some(tx),
+ rx: None,
+ }
+ }
+
+ /// Creates a transfer that receives data into `rx`.
+ pub fn read(rx: &'buf mut [u8]) -> Self {
+ Self {
+ tx: None,
+ rx: Some(rx),
+ }
+ }
+
+ /// Creates a full-duplex transfer: `tx` is transmitted while `rx` is received
+ /// simultaneously.
+ ///
+ /// The two buffers must have the same length. Controllers with the
+ /// `SPI_CONTROLLER_HALF_DUPLEX` flag (or devices in 3-wire mode) reject full-duplex
+ /// transfers with [`EINVAL`].
+ pub fn full_duplex(tx: &'buf [u8], rx: &'buf mut [u8]) -> Self {
+ Self {
+ tx: Some(tx),
+ rx: Some(rx),
+ }
+ }
+}
+
+/// Device configuration accessors and I/O operations, restricted to bound devices.
+///
+/// An `ARef<SpiDevice>` (i.e. a `SpiDevice<Normal>`) may outlive the driver's unbind and the
+/// device's or controller's unregistration. The SPI core's transfer path does not check the
+/// registration state, and the controller driver's resources (e.g. `spi->controller_state` or
+/// MMIO mappings) may already have been released, so performing I/O on an unbound device is not
+/// sound. Likewise, once the device is unbound, another driver may bind to the same
+/// `struct spi_device` and mutate the device configuration with plain, non-atomic writes (e.g.
+/// via `spi_setup()`), so reading the configuration accessors on an unbound device would be a
+/// data race. Restricting these operations to [`SpiDevice<Bound>`] guarantees that the device is
+/// still bound to a driver; driver callbacks receive a `SpiDevice<Core>`, which dereferences to
+/// `SpiDevice<Bound>`.
+impl SpiDevice<device::Bound> {
+ /// Returns the maximum speed of the SPI device.
+ #[inline]
+ pub fn max_speed_hz(&self) -> u32 {
+ // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a valid pointer to a
+ // `struct spi_device`.
+ unsafe { (*self.as_raw()).max_speed_hz }
+ }
+
+ /// Returns the number of bits per word of the SPI device.
+ #[inline]
+ pub fn bits_per_word(&self) -> u8 {
+ // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a valid pointer to a
+ // `struct spi_device`.
+ unsafe { (*self.as_raw()).bits_per_word }
+ }
+
+ /// Returns the mode flags of the SPI device.
+ #[inline]
+ pub fn mode(&self) -> u32 {
+ // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a valid pointer to a
+ // `struct spi_device`.
+ unsafe { (*self.as_raw()).mode }
+ }
+
+ /// Executes a sequence of [`Transfer`]s as a single SPI message.
+ ///
+ /// This is the primitive that all I/O methods are built on; it maps to the C `spi_sync()`
+ /// API. The transfers are executed in order with the chip select asserted for the whole
+ /// message.
+ ///
+ /// # Examples
+ ///
+ /// ```ignore
+ /// use kernel::spi::{self, Transfer};
+ ///
+ /// fn read_register(dev: &spi::SpiDevice<kernel::device::Bound>, reg: u8) -> Result<u8> {
+ /// let cmd = [reg];
+ /// let mut val = [0u8; 1];
+ /// dev.transfer(&mut [Transfer::write(&cmd), Transfer::read(&mut val)])?;
+ /// Ok(val[0])
+ /// }
+ /// ```
+ pub fn transfer(&self, transfers: &mut [Transfer<'_>]) -> Result {
+ if transfers.is_empty() {
+ return Err(EINVAL);
+ }
+
+ struct Bounce {
+ tx: KVec<u8>,
+ rx: KVec<u8>,
+ }
+
+ // `spi_sync()` requires transfer buffers to be DMA-safe, but Rust slices may be
+ // located anywhere (e.g. on the stack), so the data is copied into DMA-safe bounce
+ // buffers.
+ let mut bounces: KVec<Bounce> = KVec::with_capacity(transfers.len(), GFP_KERNEL)?;
+ let mut xfers: KVec<bindings::spi_transfer> =
+ KVec::with_capacity(transfers.len(), GFP_KERNEL)?;
+
+ for t in transfers.iter() {
+ if let (Some(tx), Some(rx)) = (&t.tx, &t.rx) {
+ if tx.len() != rx.len() {
+ return Err(EINVAL);
+ }
+ }
+
+ let tx_len = t.tx.map_or(0, |buf| buf.len());
+ let rx_len = t.rx.as_deref().map_or(0, |buf| buf.len());
+ let len = tx_len.max(rx_len);
+ if len == 0 || len > u32::MAX as usize {
+ return Err(EINVAL);
+ }
+
+ let tx = t.tx.unwrap_or(&[]);
+ let mut tx_bounce = KVec::with_capacity(tx.len(), GFP_KERNEL)?;
+ tx_bounce.extend_from_slice(tx, GFP_KERNEL)?;
+
+ let mut rx_bounce = KVec::with_capacity(rx_len, GFP_KERNEL)?;
+ rx_bounce.resize(rx_len, 0, GFP_KERNEL)?;
+
+ let xfer = bindings::spi_transfer {
+ tx_buf: if tx_bounce.is_empty() {
+ core::ptr::null()
+ } else {
+ tx_bounce.as_ptr().cast()
+ },
+ rx_buf: if rx_bounce.is_empty() {
+ core::ptr::null_mut()
+ } else {
+ rx_bounce.as_mut_ptr().cast()
+ },
+ len: len as u32,
+ ..pin_init::zeroed()
+ };
+ xfers.push(xfer, GFP_KERNEL)?;
+ bounces.push(
+ Bounce {
+ tx: tx_bounce,
+ rx: rx_bounce,
+ },
+ GFP_KERNEL,
+ )?;
+ }
+
+ let mut msg: bindings::spi_message = pin_init::zeroed();
+
+ // SAFETY: `msg` is a valid `struct spi_message`.
+ unsafe { bindings::spi_message_init(&mut msg) };
+
+ for xfer in xfers.iter_mut() {
+ // SAFETY: `xfer` is a valid `struct spi_transfer` and `msg` has been initialized
+ // by `spi_message_init()` above.
+ unsafe { bindings::spi_message_add_tail(xfer, &mut msg) };
+ }
+
+ // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a valid pointer to a
+ // `struct spi_device`. `msg` and the `struct spi_transfer`s linked into it are valid
+ // for the duration of the call, and `spi_sync()` is synchronous, so they are not
+ // accessed by the C core after it returns.
+ to_result(unsafe { bindings::spi_sync(self.as_raw(), &mut msg) })?;
+
+ for (t, bounce) in transfers.iter_mut().zip(bounces.iter_mut()) {
+ if let Some(rx) = t.rx.as_deref_mut() {
+ rx.copy_from_slice(&bounce.rx);
+ }
+ }
+
+ Ok(())
+ }
+
+ /// Writes the data from `buf` to the SPI device.
+ #[inline]
+ pub fn write(&self, buf: &[u8]) -> Result {
+ self.transfer(&mut [Transfer::write(buf)])
+ }
+
+ /// Reads data from the SPI device into `buf`.
+ #[inline]
+ pub fn read(&self, buf: &mut [u8]) -> Result {
+ self.transfer(&mut [Transfer::read(buf)])
+ }
+
+ /// Writes the data from `write_buf` to the SPI device, then reads data from the SPI device
+ /// into `read_buf`, with the chip select asserted for the whole operation.
+ ///
+ /// This performs the two phases sequentially; to transmit and receive simultaneously, use
+ /// [`Transfer::full_duplex`] with [`SpiDevice::transfer`].
+ #[inline]
+ pub fn write_then_read(&self, write_buf: &[u8], read_buf: &mut [u8]) -> Result {
+ self.transfer(&mut [Transfer::write(write_buf), Transfer::read(read_buf)])
+ }
+}
+
+// SAFETY: `SpiDevice` is a transparent wrapper of `struct spi_device`.
+// The offset is guaranteed to point to a valid device field inside `SpiDevice`.
+unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for SpiDevice<Ctx> {
+ const OFFSET: usize = offset_of!(bindings::spi_device, dev);
+}
+
+// SAFETY: `SpiDevice` is a transparent wrapper of a type that doesn't depend on
+// `SpiDevice`'s generic argument.
+kernel::impl_device_context_deref!(unsafe { SpiDevice });
+kernel::impl_device_context_into_aref!(SpiDevice);
+
+// SAFETY: Instances of `SpiDevice` are always reference-counted.
+unsafe impl AlwaysRefCounted for SpiDevice {
+ fn inc_ref(&self) {
+ // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
+ unsafe { bindings::get_device(self.as_ref().as_raw()) };
+ }
+
+ unsafe fn dec_ref(obj: NonNull<Self>) {
+ // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+ unsafe { bindings::put_device(&raw mut (*obj.as_ref().as_raw()).dev) }
+ }
+}
+
+impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for SpiDevice<Ctx> {
+ fn as_ref(&self) -> &device::Device<Ctx> {
+ let raw = self.as_raw();
+ // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
+ // `struct spi_device`.
+ let dev = unsafe { &raw mut (*raw).dev };
+
+ // SAFETY: `dev` points to a valid `struct device`.
+ unsafe { device::Device::from_raw(dev) }
+ }
+}
+
+// SAFETY: A `SpiDevice` is always reference-counted and can be released from any thread.
+unsafe impl Send for SpiDevice {}
+
+// SAFETY: `SpiDevice` can be shared among threads because `SpiDevice<Normal>` has no methods
+// that could mutate the device state or race with the C core (the configuration accessors and
+// I/O operations are restricted to `SpiDevice<Bound>`).
+unsafe impl Sync for SpiDevice {}
+
+// SAFETY: Same as `SpiDevice<Normal>` -- the underlying `struct spi_device` is the same;
+// `Bound` is a zero-sized type-state marker that does not affect thread safety.
+unsafe impl Sync for SpiDevice<device::Bound> {}
+
+#[cfg(CONFIG_RUST_SPI_KUNIT_TEST)]
+#[kunit_tests(rust_kernel_spi)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn device_id_name_size() {
+ assert_eq!(DeviceId::SPI_NAME_SIZE, bindings::SPI_NAME_SIZE as usize);
+ }
+
+ #[test]
+ fn device_id_new_short_name() {
+ let id = DeviceId::new(c"rust_driver_spi");
+
+ let expected: &[u8] = b"rust_driver_spi\0";
+ assert_eq!(&id.0.name[..expected.len()], expected);
+
+ // The remaining bytes must be zeroed.
+ assert!(id.0.name[expected.len()..].iter().all(|&byte| byte == 0));
+ }
+
+ #[test]
+ fn device_id_new_empty_name() {
+ let id = DeviceId::new(c"");
+
+ assert!(id.0.name.iter().all(|&byte| byte == 0));
+ }
+
+ #[test]
+ fn device_id_new_max_length_name() {
+ // 31 bytes plus the NUL terminator is the maximum accepted name length.
+ let id = DeviceId::new(c"abcdefghijklmnopqrstuvwxyz01234");
+
+ let expected: &[u8] = b"abcdefghijklmnopqrstuvwxyz01234\0";
+ assert_eq!(&id.0.name[..], expected);
+ }
+}
--
2.43.0
^ permalink raw reply [flat|nested] 4+ messages in thread* [PATCH v8 3/3] samples: rust: add SPI driver sample
[not found] ` <20261114010745.82389-1-847807867@qq.com>
2026-11-14 1:07 ` [PATCH v8 2/3] rust: spi: add SPI driver abstractions Shuai Liu
@ 2026-11-14 1:07 ` Shuai Liu
1 sibling, 0 replies; 4+ messages in thread
From: Shuai Liu @ 2026-11-14 1:07 UTC (permalink / raw)
To: linux-spi
Cc: rust-for-linux, Mark Brown, ojeda, dakr, linux-kernel, 847807867
Add a sample driver for the Rust SPI abstractions to demonstrate their
usage.
Signed-off-by: Shuai Liu <847807867@qq.com>
---
samples/rust/Kconfig | 11 ++++++
samples/rust/Makefile | 1 +
samples/rust/rust_driver_spi.rs | 66 +++++++++++++++++++++++++++++++++
3 files changed, 78 insertions(+)
create mode 100644 samples/rust/rust_driver_spi.rs
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index 31d62533ef25f..f99bf52654a15 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -84,6 +84,17 @@ config SAMPLE_RUST_DEBUGFS_SCOPED
If unsure, say N.
+config SAMPLE_RUST_DRIVER_SPI
+ tristate "SPI Driver"
+ depends on SPI=y
+ help
+ This option builds the Rust SPI driver sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_driver_spi.
+
+ If unsure, say N.
+
config SAMPLE_RUST_DRIVER_I2C
tristate "I2C Driver"
depends on I2C=y
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index b986b681cde5a..efe04638a990b 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_SAMPLE_RUST_DEBUGFS) += rust_debugfs.o
obj-$(CONFIG_SAMPLE_RUST_DEBUGFS_SCOPED) += rust_debugfs_scoped.o
obj-$(CONFIG_SAMPLE_RUST_DMA) += rust_dma.o
obj-$(CONFIG_SAMPLE_RUST_DRIVER_I2C) += rust_driver_i2c.o
+obj-$(CONFIG_SAMPLE_RUST_DRIVER_SPI) += rust_driver_spi.o
obj-$(CONFIG_SAMPLE_RUST_I2C_CLIENT) += rust_i2c_client.o
obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI) += rust_driver_pci.o
obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM) += rust_driver_platform.o
diff --git a/samples/rust/rust_driver_spi.rs b/samples/rust/rust_driver_spi.rs
new file mode 100644
index 0000000000000..7eee7b7357947
--- /dev/null
+++ b/samples/rust/rust_driver_spi.rs
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust SPI driver sample.
+
+use kernel::{
+ device::Core,
+ of,
+ prelude::*,
+ spi, //
+};
+
+struct SampleDriver;
+
+kernel::spi_device_table! {
+ SPI_TABLE,
+ <SampleDriver as spi::Driver>::IdInfo,
+ [(spi::DeviceId::new(c"rust_driver_spi"), 0)]
+}
+
+kernel::of_device_table! {
+ OF_TABLE,
+ <SampleDriver as spi::Driver>::IdInfo,
+ [(of::DeviceId::new(c"test,rust_driver_spi"), 0)]
+}
+
+impl spi::Driver for SampleDriver {
+ type IdInfo = u32;
+ type Data<'bound> = Self;
+
+ const SPI_ID_TABLE: Option<spi::IdTable<Self::IdInfo>> = Some(&SPI_TABLE);
+ const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+
+ fn probe<'bound>(
+ sdev: &'bound spi::SpiDevice<Core<'_>>,
+ info: Option<&'bound Self::IdInfo>,
+ ) -> impl PinInit<Self, Error> + 'bound {
+ let dev = sdev.as_ref();
+
+ dev_info!(dev, "Probe Rust SPI driver sample.\n");
+ dev_info!(dev, "max_speed_hz: {}.\n", sdev.max_speed_hz());
+ dev_info!(dev, "bits_per_word: {}.\n", sdev.bits_per_word());
+ dev_info!(dev, "mode: {:#x}.\n", sdev.mode());
+
+ if let Some(info) = info {
+ dev_info!(dev, "Probed with info: '{}'.\n", info);
+ }
+
+ Ok(Self)
+ }
+
+ fn shutdown<'bound>(sdev: &'bound spi::SpiDevice<Core<'_>>, _this: Pin<&Self>) {
+ dev_info!(sdev.as_ref(), "Shutdown Rust SPI driver sample.\n");
+ }
+
+ fn unbind<'bound>(sdev: &'bound spi::SpiDevice<Core<'_>>, _this: Pin<&Self>) {
+ dev_info!(sdev.as_ref(), "Unbind Rust SPI driver sample.\n");
+ }
+}
+
+kernel::module_spi_driver! {
+ type: SampleDriver,
+ name: "rust_driver_spi",
+ authors: ["Shuai Liu"],
+ description: "Rust SPI driver",
+ license: "GPL v2",
+}
--
2.43.0
^ permalink raw reply [flat|nested] 4+ messages in thread