[PATCH v8 0/4] rust: i2c: Add basic I2C driver abstractions

[PATCH v8 0/4] rust: i2c: Add basic I2C driver abstractions

[Igor Korotin]

This patch series lays the groundwork for writing Linux I2C drivers in 
Rust by:

 1. Core abstractions 
    Introduce `i2c::I2cClient`, `i2c::I2cAdapter`, `i2c::Driver` and 
    built on the existing `struct i2c_client`, `struct i2c_adapter` 
    and `struct i2c_driver`, with safe Rust wrappers around probe, 
    transfer, and teardown logic.

 2. Manual device creation  
    Provide an API to register an I2C device at runtime from Rust using
    `I2cBoardInfo` and `I2cAdapter`, including automatic cleanup when 
    the driver unloads.

 3. Sample I2C driver (legacy table, OF & ACPI)  
    Add `rust_driver_i2c`, a sample that:
      - binds to an I2C client via: 
        - legacy I2C-ID table, 
        - Open Firmware (device-tree) compatible strings, or
        - ACPI IDs.
 4. Sample I2C client registration (OF & ACPI)
    Add `rust_i2c_client`, a sample that:
      - binds to a platform parent device using OF/ACPI table
      - registers new I2C client bound to the parent platform device
        using `i2c::Registration::new()`
      - destroyes the I2C client device on exit.

Together, these four patches:

- Establish the essential Rust traits and types for I2C drivers.
- Enable driver binding via legacy ID table, device-tree (OF), or ACPI
- Enable manual device creation at runtime.
- Ship a samples showing typical usage 

Igor Korotin (4):
  rust: i2c: add basic I2C device and driver abstractions
  rust: i2c: add manual I2C device creation abstractions
  samples: rust: add Rust I2C sample driver
  samples: rust: add Rust I2C client registration sample

Changelog
---------
v8:
 - Rebase commits on top of [1]
 - Applied kernel vertical style [2] 
 - Replace core::mem::zeroed() with pin_init::zeroed()
 - Rename `I2cAdapter::get_nr` to `I2cAdapter::index`
 - fixed some minor format issues
 - Link to v7: [3]

 [1] https://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git/log/?h=driver-core-next
 [2] https://docs.kernel.org/rust/coding-guidelines.html#imports
 [3] https://lore.kernel.org/rust-for-linux/20251110112437.50405-1-igor.korotin.linux@gmail.com/

v7:
 - Rebase and update `i2c::Driver::probe` function based on patch 
   series [1].
 - use `i2c::Driver::unbind` instead of `drop` in 
   `i2c::Adapter::remove_callback`
 - Implement and use `i2c::Driver::unbind` for I2C SampleDriver
   instead of Drop.
 - `i2c::Registration::new` requires a parent device to which a new
   I2C client will be bound. 
 - `i2c::Registration::new` returns `impl PinInit<Devres<Self>, Error>`
 - The existing rust_driver_i2c sample has been split into two:
   `rust_driver_i2c`, which demonstrates the implementation of an I2C 
   driver, and `rust_i2c_client`, which demonstrates registering a new 
   I2C client bound to a parent platform device.
 - Link to v6: [2]

 [1] https://lore.kernel.org/all/20251016125544.15559-1-dakr@kernel.org/
 [2] https://lore.kernel.org/rust-for-linux/20251005102226.41876-1-igor.korotin.linux@gmail.com/ 

v6:
 - Add implementation of unbind for `i2c::Driver` trait;
 - Add argument `Pin<&Self>` to `i2c::Driver::shutdown` method; 
 - Adjust usage of `i2c::Driver::shutdown` in 
   `i2c::Adapter::shutdown_callback` in `i2c::Driver` trait code 
   example and in rust_driver_i2c code;
 - Remove dummy AsRef implementation for I2cAdapter. Adjust code 
   in rust_driver_i2c;
 - Add `i2c::I2cAdapter::get_nr` method that returns I2cAdapter index;
 - Optimize unsafe sections in inc_ref/dec_ref in AlwaysRefCounted 
   for I2cAdapter implementation;
 - Remove unnecessary Drop implementation for I2cAdapter, because 
   I2cAdapter is always a reference;
 - Remove unnecessary type definition `Ops<T>` in rust_driver_i2c
 - Simplify call of `i2c::I2cAdapter::get` in `try_pin_init!` macro 
   for rust_driver_i2c
 - Link to v5: https://lore.kernel.org/rust-for-linux/20250911154717.96637-1-igor.korotin.linux@gmail.com/ 
v5:
 - Rename missed pdev variables to idev (thanks to Daniel).
 - Import `crate::device_id::RawDeviceIdIndex` and 
   `crate::types::AlwaysRefCounted` in i2c.rs.
 - Switch dev_dbg to dev_info in the sample I2C driver messages.
 - Make `I2cAdapter::get()` return `ARef<I2cAdapter>` instead of 
   `&I2cAdapter`.
 - Remove `TryFrom<device::Device<Ctx>> for I2cAdapter<Ctx>` (unused; 
   to be reintroduced in a later I2C series).
 - Remove `AsRef<device::Device<Ctx>> for I2cAdapter<Ctx>` (unused; 
   to be reintroduced in a later I2C series).
 - Add `AsRef<I2cAdapter> for I2cAdapter<Ctx>`.
 - Use i2c_get/put_adapter instead of get/put_device for 
   `AlwaysRefCounted<I2cAdapter>`.
 - Update safety comment for `unsafe impl Sync for Registration {}`.
 - Tweak comment for `I2cBoardInfo::new`.
 - Adjust build-time assertion message in `Adapter::register`.
 - Link to v4: https://lore.kernel.org/rust-for-linux/20250820151427.1812482-1-igor.korotin.linux@gmail.com/ 
v4:
 - Renamed `i2c::I2cAdapterRef` to `i2c::I2cAdapter`.
 - Renamed `i2c::Device` to `i2c::I2cClient` for consistency with 
   `i2c::I2cAdapter` and to avoid confusion with `i2c::Adapter`
 - Reworked `i2c::I2cAdapter` to be an Opaque around `i2c_adapter` struct
 - Implemented AlwaysRefCounted trait for `i2c::I2cAdapter`. 
 - Fixed numerous comment mistakes and typos all over the code, thanks 
   to Danilo and Daniel
 - Got rid of all unwrap() use-cases in i2c.rs and rust_driver_i2c.rs.
   This covers 0-day kernel panic <202508071027.8981cbd4-lkp@intel.com>
 - Removed unnecessary casts.
 - Replaced all addr_of_mut! macros to &raw mut.
 - In `i2c::Adapter::register` method build assert if all ID tables are 
   None.
 - Renamed all pdrv and pdev instances to idrv and idev respectivly 
 - Implemented an ealry return in `i2c::Adapter::i2c_id_info`
 - Added all missing Safety comments. 
 - Removed `unsafe impl<Ctx: device::DeviceContext> crate::types::AlwaysRefCounted for Device<Ctx>` 
   implementation which came to v3 from v2 by mistake.
 - Added more details regarding i2c-stub driver usage in rust_driver_i2c
   comment.
 - Changed `i2c::I2cAdapter::get` return type from `Option<Self>` to 
   `Result<&'static Self>`.
 - Added Daniel Almeida as a reviewer to the "I2C Subsystem [RUST]" entry 
   in MAINTAINERS, per his offer.
 - Link to v3: https://lore.kernel.org/rust-for-linux/20250801153742.13472-1-igor.korotin.linux@gmail.com/
v3: 
 - removed unnecessary i2c_get_clientdata and i2c_set_clientdata rust 
   helpers. Using generic accessors implemented in [1] instead.
 - Reimplemented i2c::DeviceId based on changes in [2].
 - Using from_result in i2c::Adapter::probe_callback
 - Using explicit drop() for i2c client private data in 
   `i2c::Adapter::remove_callback`
 - replaced device::Device::as_ref() with device::Device::from_raw in 
   `i2c::Device::as_ref()`. It is renamed in device::Device.
 - Build Rust I2C only if I2C is built-in
 - Reimplement overcomplicated trait i2c::DeviceOwned the same way it is 
   implemented in auxiliary [3].
 - Merge rust_device_i2c and rust_driver_i2c samples. Resulting 
   rust_driver_i2c creates pined i2c_client using i2c::Registration::new 
   and probes newly created i2c_client.
 - Created a new entry in MAINTAINERS file containing i2c.rs and 
   rust_driver_i2c.rs in it.
 - Link to v2: [4] 

 [1] https://lore.kernel.org/lkml/20250621195118.124245-3-dakr@kernel.org/
 [2] https://lore.kernel.org/rust-for-linux/20250711040947.1252162-1-fujita.tomonori@gmail.com/
 [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/rust/kernel/auxiliary.rs?h=v6.16-rc4#n299
 [4] https://lore.kernel.org/rust-for-linux/20250704153332.1193214-1-igor.korotin.linux@gmail.com/ 

v2:
 - Merged separated ACPI support patches since ACPI-table support is 
   merged into driver-core-next.
 - Added I2cAdapterRef and I2cBoardInfo abstractions 
 - Added DeviceState generic parameter which is used for `i2c::Device`
   as a sign if the device is created manually
 - Added `DeviceOwned` abstraction which is a safe reference to a 
   manually created `i2c::Device<Ctx, state::Owned>`. 
 - Added Rust manual I2C device creation sample
 - Link to v1: https://lore.kernel.org/rust-for-linux/20250626174623.904917-1-igor.korotin.linux@gmail.com/

 MAINTAINERS                     |   9 +
 rust/bindings/bindings_helper.h |   1 +
 rust/kernel/i2c.rs              | 589 ++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |   2 +
 samples/rust/Kconfig            |  23 ++
 samples/rust/Makefile           |   2 +
 samples/rust/rust_driver_i2c.rs |  74 ++++
 samples/rust/rust_i2c_client.rs | 157 +++++++++
 8 files changed, 857 insertions(+)
 create mode 100644 rust/kernel/i2c.rs
 create mode 100644 samples/rust/rust_driver_i2c.rs
 create mode 100644 samples/rust/rust_i2c_client.rs


base-commit: ededb7bcdfdbcfbb7af93e3a543165a9553e1683
-- 
2.43.0

[PATCH v8 1/4] rust: i2c: add basic I2C device and driver abstractions

[Igor Korotin]

Implement the core abstractions needed for I2C drivers, including:

* `i2c::Driver` — the trait drivers must implement, including `probe`

* `i2c::I2cClient` — a safe wrapper around `struct i2c_client`

* `i2c::Adapter` — implements `driver::RegistrationOps` to hook into the
  generic `driver::Registration` machinery

* `i2c::DeviceId` — a `RawDeviceIdIndex` implementation for I2C device IDs

Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
---
 MAINTAINERS                     |   8 +
 rust/bindings/bindings_helper.h |   1 +
 rust/kernel/i2c.rs              | 436 ++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |   2 +
 4 files changed, 447 insertions(+)
 create mode 100644 rust/kernel/i2c.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 3da2c26a796b..a8dfde2f5633 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11743,6 +11743,14 @@ F:	include/linux/i2c.h
 F:	include/uapi/linux/i2c-*.h
 F:	include/uapi/linux/i2c.h
 
+I2C SUBSYSTEM [RUST]
+M:	Igor Korotin <igor.korotin.linux@gmail.com>
+R:	Danilo Krummrich <dakr@kernel.org>
+R:	Daniel Almeida <daniel.almeida@collabora.com>
+L:	rust-for-linux@vger.kernel.org
+S:	Maintained
+F:	rust/kernel/i2c.rs
+
 I2C SUBSYSTEM HOST DRIVERS
 M:	Andi Shyti <andi.shyti@kernel.org>
 L:	linux-i2c@vger.kernel.org
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index a79fd111f886..f92abb578b56 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -58,6 +58,7 @@
 #include <linux/firmware.h>
 #include <linux/interrupt.h>
 #include <linux/fs.h>
+#include <linux/i2c.h>
 #include <linux/ioport.h>
 #include <linux/jiffies.h>
 #include <linux/jump_label.h>
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
new file mode 100644
index 000000000000..a5ad8213d9ac
--- /dev/null
+++ b/rust/kernel/i2c.rs
@@ -0,0 +1,436 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! I2C Driver subsystem
+
+// I2C Driver abstractions.
+use crate::{
+    acpi,
+    container_of,
+    device,
+    device_id::{
+        RawDeviceId,
+        RawDeviceIdIndex, //
+    },
+    driver,
+    error::*,
+    of,
+    prelude::*,
+    types::{
+        AlwaysRefCounted,
+        Opaque, //
+    }, //
+};
+
+use core::{
+    marker::PhantomData,
+    ptr::NonNull, //
+};
+
+/// An I2C device id table.
+#[repr(transparent)]
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::i2c_device_id);
+
+impl DeviceId {
+    const I2C_NAME_SIZE: usize = 20;
+
+    /// Create a new device id from an I2C 'id' string.
+    #[inline(always)]
+    pub const fn new(id: &'static CStr) -> Self {
+        build_assert!(
+            id.len_with_nul() <= Self::I2C_NAME_SIZE,
+            "ID exceeds 20 bytes"
+        );
+        let src = id.as_bytes_with_nul();
+        // Replace with `bindings::i2c_device_id::default()` once stabilized for `const`.
+        // SAFETY: FFI type is valid to be zero-initialized.
+        let mut i2c: bindings::i2c_device_id = pin_init::zeroed();
+        let mut i = 0;
+        while i < src.len() {
+            i2c.name[i] = src[i];
+            i += 1;
+        }
+
+        Self(i2c)
+    }
+}
+
+// SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `i2c_device_id` and does not add
+// additional invariants, so it's safe to transmute to `RawType`.
+unsafe impl RawDeviceId for DeviceId {
+    type RawType = bindings::i2c_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::i2c_device_id, driver_data);
+
+    fn index(&self) -> usize {
+        self.0.driver_data
+    }
+}
+
+/// IdTable type for I2C
+pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
+
+/// Create a I2C `IdTable` with its alias for modpost.
+#[macro_export]
+macro_rules! i2c_device_table {
+    ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
+        const $table_name: $crate::device_id::IdArray<
+            $crate::i2c::DeviceId,
+            $id_info_type,
+            { $table_data.len() },
+        > = $crate::device_id::IdArray::new($table_data);
+
+        $crate::module_device_table!("i2c", $module_table_name, $table_name);
+    };
+}
+
+/// An adapter for the registration of I2C drivers.
+pub struct Adapter<T: Driver>(T);
+
+// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
+// a preceding call to `register` has been successful.
+unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
+    type RegType = bindings::i2c_driver;
+
+    unsafe fn register(
+        idrv: &Opaque<Self::RegType>,
+        name: &'static CStr,
+        module: &'static ThisModule,
+    ) -> Result {
+        build_assert!(
+            T::ACPI_ID_TABLE.is_some() || T::OF_ID_TABLE.is_some() || T::I2C_ID_TABLE.is_some(),
+            "At least one of ACPI/OF/Legacy tables must be present when registering an i2c driver"
+        );
+
+        let i2c_table = match T::I2C_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 i2c_client` on initialization.
+        unsafe {
+            (*idrv.get()).driver.name = name.as_char_ptr();
+            (*idrv.get()).probe = Some(Self::probe_callback);
+            (*idrv.get()).remove = Some(Self::remove_callback);
+            (*idrv.get()).shutdown = Some(Self::shutdown_callback);
+            (*idrv.get()).id_table = i2c_table;
+            (*idrv.get()).driver.of_match_table = of_table;
+            (*idrv.get()).driver.acpi_match_table = acpi_table;
+        }
+
+        // SAFETY: `idrv` is guaranteed to be a valid `RegType`.
+        to_result(unsafe { bindings::i2c_register_driver(module.0, idrv.get()) })
+    }
+
+    unsafe fn unregister(idrv: &Opaque<Self::RegType>) {
+        // SAFETY: `idrv` is guaranteed to be a valid `RegType`.
+        unsafe { bindings::i2c_del_driver(idrv.get()) }
+    }
+}
+
+impl<T: Driver + 'static> Adapter<T> {
+    extern "C" fn probe_callback(idev: *mut bindings::i2c_client) -> kernel::ffi::c_int {
+        // SAFETY: The I2C bus only ever calls the probe callback with a valid pointer to a
+        // `struct i2c_client`.
+        //
+        // INVARIANT: `idev` is valid for the duration of `probe_callback()`.
+        let idev = unsafe { &*idev.cast::<I2cClient<device::CoreInternal>>() };
+
+        let info =
+            Self::i2c_id_info(idev).or_else(|| <Self as driver::Adapter>::id_info(idev.as_ref()));
+
+        from_result(|| {
+            let data = T::probe(idev, info);
+
+            idev.as_ref().set_drvdata(data)?;
+            Ok(0)
+        })
+    }
+
+    extern "C" fn remove_callback(idev: *mut bindings::i2c_client) {
+        // SAFETY: `idev` is a valid pointer to a `struct i2c_client`.
+        let idev = unsafe { &*idev.cast::<I2cClient<device::CoreInternal>>() };
+
+        // SAFETY: `remove_callback` is only ever called after a successful call to
+        // `probe_callback`, hence it's guaranteed that `I2cClient::set_drvdata()` has been called
+        // and stored a `Pin<KBox<T>>`.
+        let data = unsafe { idev.as_ref().drvdata_obtain::<T>() };
+
+        T::unbind(idev, data.as_ref());
+    }
+
+    extern "C" fn shutdown_callback(idev: *mut bindings::i2c_client) {
+        // SAFETY: `shutdown_callback` is only ever called for a valid `idev`
+        let idev = unsafe { &*idev.cast::<I2cClient<device::CoreInternal>>() };
+
+        // SAFETY: `shutdown_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<T>>`.
+        let data = unsafe { idev.as_ref().drvdata_obtain::<T>() };
+
+        T::shutdown(idev, data.as_ref());
+    }
+
+    /// The [`i2c::IdTable`] of the corresponding driver.
+    fn i2c_id_table() -> Option<IdTable<<Self as driver::Adapter>::IdInfo>> {
+        T::I2C_ID_TABLE
+    }
+
+    /// Returns the driver's private data from the matching entry in the [`i2c::IdTable`], if any.
+    ///
+    /// If this returns `None`, it means there is no match with an entry in the [`i2c::IdTable`].
+    fn i2c_id_info(dev: &I2cClient) -> Option<&'static <Self as driver::Adapter>::IdInfo> {
+        let table = Self::i2c_id_table()?;
+
+        // SAFETY:
+        // - `table` has static lifetime, hence it's valid for reads
+        // - `dev` is guaranteed to be valid while it's alive, and so is `dev.as_raw()`.
+        let raw_id = unsafe { bindings::i2c_match_id(table.as_ptr(), dev.as_raw()) };
+
+        if raw_id.is_null() {
+            return None;
+        }
+
+        // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of `struct i2c_device_id` and
+        // does not add additional invariants, so it's safe to transmute.
+        let id = unsafe { &*raw_id.cast::<DeviceId>() };
+
+        Some(table.info(<DeviceId as RawDeviceIdIndex>::index(id)))
+    }
+}
+
+impl<T: Driver + 'static> 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 i2c driver.
+///
+/// # Examples
+///
+/// ```ignore
+/// kernel::module_i2c_driver! {
+///     type: MyDriver,
+///     name: "Module name",
+///     authors: ["Author name"],
+///     description: "Description",
+///     license: "GPL v2",
+/// }
+/// ```
+#[macro_export]
+macro_rules! module_i2c_driver {
+    ($($f:tt)*) => {
+        $crate::module_driver!(<T>, $crate::i2c::Adapter<T>, { $($f)* });
+    };
+}
+
+/// The i2c driver trait.
+///
+/// Drivers must implement this trait in order to get a i2c driver registered.
+///
+/// # Example
+///
+///```
+/// # use kernel::{acpi, bindings, c_str, device::Core, i2c, of};
+///
+/// struct MyDriver;
+///
+/// kernel::acpi_device_table!(
+///     ACPI_TABLE,
+///     MODULE_ACPI_TABLE,
+///     <MyDriver as i2c::Driver>::IdInfo,
+///     [
+///         (acpi::DeviceId::new(c_str!("LNUXBEEF")), ())
+///     ]
+/// );
+///
+/// kernel::i2c_device_table!(
+///     I2C_TABLE,
+///     MODULE_I2C_TABLE,
+///     <MyDriver as i2c::Driver>::IdInfo,
+///     [
+///          (i2c::DeviceId::new(c_str!("rust_driver_i2c")), ())
+///     ]
+/// );
+///
+/// kernel::of_device_table!(
+///     OF_TABLE,
+///     MODULE_OF_TABLE,
+///     <MyDriver as i2c::Driver>::IdInfo,
+///     [
+///         (of::DeviceId::new(c_str!("test,device")), ())
+///     ]
+/// );
+///
+/// impl i2c::Driver for MyDriver {
+///     type IdInfo = ();
+///     const I2C_ID_TABLE: Option<i2c::IdTable<Self::IdInfo>> = Some(&I2C_TABLE);
+///     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(
+///         _idev: &i2c::I2cClient<Core>,
+///         _id_info: Option<&Self::IdInfo>,
+///     ) -> impl PinInit<Self, Error> {
+///         Err(ENODEV)
+///     }
+///
+///     fn shutdown(_idev: &i2c::I2cClient<Core>, this: Pin<&Self>) {
+///     }
+/// }
+///```
+pub trait Driver: Send {
+    /// 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 table of device ids supported by the driver.
+    const I2C_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;
+
+    /// I2C driver probe.
+    ///
+    /// Called when a new i2c client is added or discovered.
+    /// Implementers should attempt to initialize the client here.
+    fn probe(
+        dev: &I2cClient<device::Core>,
+        id_info: Option<&Self::IdInfo>,
+    ) -> impl PinInit<Self, Error>;
+
+    /// I2C driver shutdown.
+    ///
+    /// Called by the kernel during system reboot or power-off to allow the [`Driver`] to bring the
+    /// [`Device`] 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 `Self::drop`.
+    fn shutdown(dev: &I2cClient<device::Core>, this: Pin<&Self>) {
+        let _ = (dev, this);
+    }
+
+    /// I2C 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, drivers may try to perform I/O
+    /// operations to gracefully tear down the device.
+    ///
+    /// Otherwise, release operations for driver resources should be performed in `Self::drop`.
+    fn unbind(dev: &I2cClient<device::Core>, this: Pin<&Self>) {
+        let _ = (dev, this);
+    }
+}
+
+/// The i2c client representation.
+///
+/// This structure represents the Rust abstraction for a C `struct i2c_client`. The
+/// implementation abstracts the usage of an existing C `struct i2c_client` that
+/// gets passed from the C side
+///
+/// # Invariants
+///
+/// A [`I2cClient`] instance represents a valid `struct i2c_client` created by the C portion of
+/// the kernel.
+#[repr(transparent)]
+pub struct I2cClient<Ctx: device::DeviceContext = device::Normal>(
+    Opaque<bindings::i2c_client>,
+    PhantomData<Ctx>,
+);
+
+impl<Ctx: device::DeviceContext> I2cClient<Ctx> {
+    fn as_raw(&self) -> *mut bindings::i2c_client {
+        self.0.get()
+    }
+}
+
+// SAFETY: `I2cClient` is a transparent wrapper of a type that doesn't depend on
+// `I2cClient`'s generic argument.
+kernel::impl_device_context_deref!(unsafe { I2cClient });
+kernel::impl_device_context_into_aref!(I2cClient);
+
+// SAFETY: Instances of `I2cClient` are always reference-counted.
+unsafe impl AlwaysRefCounted for I2cClient {
+    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 I2cClient<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 i2c_client`.
+        let dev = unsafe { &raw mut (*raw).dev };
+
+        // SAFETY: `dev` points to a valid `struct device`.
+        unsafe { device::Device::from_raw(dev) }
+    }
+}
+
+impl<Ctx: device::DeviceContext> TryFrom<&device::Device<Ctx>> for &I2cClient<Ctx> {
+    type Error = kernel::error::Error;
+
+    fn try_from(dev: &device::Device<Ctx>) -> Result<Self, Self::Error> {
+        // SAFETY: By the type invariant of `Device`, `dev.as_raw()` is a valid pointer to a
+        // `struct device`.
+        if unsafe { bindings::i2c_verify_client(dev.as_raw()).is_null() } {
+            return Err(EINVAL);
+        }
+
+        // SAFETY: We've just verified that the type of `dev` equals to
+        // `bindings::i2c_client_type`, hence `dev` must be embedded in a valid
+        // `struct i2c_client` as guaranteed by the corresponding C code.
+        let idev = unsafe { container_of!(dev.as_raw(), bindings::i2c_client, dev) };
+
+        // SAFETY: `idev` is a valid pointer to a `struct i2c_client`.
+        Ok(unsafe { &*idev.cast() })
+    }
+}
+
+// SAFETY: A `I2cClient` is always reference-counted and can be released from any thread.
+unsafe impl Send for I2cClient {}
+
+// SAFETY: `I2cClient` can be shared among threads because all methods of `I2cClient`
+// (i.e. `I2cClient<Normal>) are thread safe.
+unsafe impl Sync for I2cClient {}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 3dd7bebe7888..8c0070a8029e 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -94,6 +94,8 @@
 pub mod firmware;
 pub mod fmt;
 pub mod fs;
+#[cfg(CONFIG_I2C = "y")]
+pub mod i2c;
 pub mod id_pool;
 pub mod init;
 pub mod io;
-- 
2.43.0

[PATCH v8 2/4] rust: i2c: add manual I2C device creation abstractions

[Igor Korotin]

In addition to the basic I2C device support, add rust abstractions
upon `i2c_new_client_device`/`i2c_unregister_device` C functions.

Implement the core abstractions needed for manual creation/deletion
of I2C devices, including:

 * `i2c::Registration` — a NonNull pointer created by the function
                          `i2c_new_client_device`

 * `i2c::I2cAdapter` — a ref counted wrapper around `struct i2c_adapter`

 * `i2c::I2cBoardInfo` — a safe wrapper around `struct i2c_board_info`

Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
---
 rust/kernel/i2c.rs | 155 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 154 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index a5ad8213d9ac..3695b4adf436 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -11,6 +11,7 @@
         RawDeviceId,
         RawDeviceIdIndex, //
     },
+    devres::Devres,
     driver,
     error::*,
     of,
@@ -23,9 +24,14 @@
 
 use core::{
     marker::PhantomData,
-    ptr::NonNull, //
+    ptr::{
+        from_ref,
+        NonNull, //
+    }, //
 };
 
+use kernel::types::ARef;
+
 /// An I2C device id table.
 #[repr(transparent)]
 #[derive(Clone, Copy)]
@@ -356,6 +362,102 @@ fn unbind(dev: &I2cClient<device::Core>, this: Pin<&Self>) {
     }
 }
 
+/// The i2c adapter representation.
+///
+/// This structure represents the Rust abstraction for a C `struct i2c_adapter`. The
+/// implementation abstracts the usage of an existing C `struct i2c_adapter` that
+/// gets passed from the C side
+///
+/// # Invariants
+///
+/// A [`I2cAdapter`] instance represents a valid `struct i2c_adapter` created by the C portion of
+/// the kernel.
+#[repr(transparent)]
+pub struct I2cAdapter<Ctx: device::DeviceContext = device::Normal>(
+    Opaque<bindings::i2c_adapter>,
+    PhantomData<Ctx>,
+);
+
+impl<Ctx: device::DeviceContext> I2cAdapter<Ctx> {
+    fn as_raw(&self) -> *mut bindings::i2c_adapter {
+        self.0.get()
+    }
+}
+
+impl I2cAdapter {
+    /// Returns the I2C Adapter index.
+    #[inline]
+    pub fn index(&self) -> i32 {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct i2c_adapter`.
+        unsafe { (*self.as_raw()).nr }
+    }
+
+    /// Gets pointer to an `i2c_adapter` by index.
+    pub fn get(index: i32) -> Result<ARef<Self>> {
+        // SAFETY: `index` must refer to a valid I2C adapter; the kernel
+        // guarantees that `i2c_get_adapter(index)` returns either a valid
+        // pointer or NULL. `NonNull::new` guarantees the correct check.
+        let adapter = NonNull::new(unsafe { bindings::i2c_get_adapter(index) }).ok_or(ENODEV)?;
+
+        // SAFETY: `adapter` is non-null and points to a live `i2c_adapter`.
+        // `I2cAdapter` is #[repr(transparent)], so this cast is valid.
+        Ok(unsafe { (&*adapter.as_ptr().cast::<I2cAdapter<device::Normal>>()).into() })
+    }
+}
+
+// SAFETY: `I2cAdapter` is a transparent wrapper of a type that doesn't depend on
+// `I2cAdapter`'s generic argument.
+kernel::impl_device_context_deref!(unsafe { I2cAdapter });
+kernel::impl_device_context_into_aref!(I2cAdapter);
+
+// SAFETY: Instances of `I2cAdapter` are always reference-counted.
+unsafe impl crate::types::AlwaysRefCounted for I2cAdapter {
+    fn inc_ref(&self) {
+        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
+        unsafe { bindings::i2c_get_adapter(self.index()) };
+    }
+
+    unsafe fn dec_ref(obj: NonNull<Self>) {
+        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+        unsafe { bindings::i2c_put_adapter(obj.as_ref().as_raw()) }
+    }
+}
+
+/// The i2c board info representation
+///
+/// This structure represents the Rust abstraction for a C `struct i2c_board_info` structure,
+/// which is used for manual I2C client creation.
+#[repr(transparent)]
+pub struct I2cBoardInfo(bindings::i2c_board_info);
+
+impl I2cBoardInfo {
+    const I2C_TYPE_SIZE: usize = 20;
+    /// Create a new [`I2cBoardInfo`] for a kernel driver.
+    #[inline(always)]
+    pub const fn new(type_: &'static CStr, addr: u16) -> Self {
+        build_assert!(
+            type_.len_with_nul() <= Self::I2C_TYPE_SIZE,
+            "Type exceeds 20 bytes"
+        );
+        let src = type_.as_bytes_with_nul();
+        // Replace with `bindings::i2c_board_info::default()` once stabilized for `const`.
+        // SAFETY: FFI type is valid to be zero-initialized.
+        let mut i2c_board_info: bindings::i2c_board_info = pin_init::zeroed();
+        let mut i: usize = 0;
+        while i < src.len() {
+            i2c_board_info.type_[i] = src[i];
+            i += 1;
+        }
+
+        i2c_board_info.addr = addr;
+        Self(i2c_board_info)
+    }
+
+    fn as_raw(&self) -> *const bindings::i2c_board_info {
+        from_ref(&self.0)
+    }
+}
+
 /// The i2c client representation.
 ///
 /// This structure represents the Rust abstraction for a C `struct i2c_client`. The
@@ -434,3 +536,54 @@ unsafe impl Send for I2cClient {}
 // SAFETY: `I2cClient` can be shared among threads because all methods of `I2cClient`
 // (i.e. `I2cClient<Normal>) are thread safe.
 unsafe impl Sync for I2cClient {}
+
+/// The registration of an i2c client device.
+///
+/// This type represents the registration of a [`struct i2c_client`]. When an instance of this
+/// type is dropped, its respective i2c client device will be unregistered from the system.
+///
+/// # Invariants
+///
+/// `self.0` always holds a valid pointer to an initialized and registered
+/// [`struct i2c_client`].
+#[repr(transparent)]
+pub struct Registration(NonNull<bindings::i2c_client>);
+
+impl Registration {
+    /// The C `i2c_new_client_device` function wrapper for manual I2C client creation.
+    pub fn new<'a>(
+        i2c_adapter: &I2cAdapter,
+        i2c_board_info: &I2cBoardInfo,
+        parent_dev: &'a device::Device<device::Bound>,
+    ) -> impl PinInit<Devres<Self>, Error> + 'a {
+        Devres::new(parent_dev, Self::try_new(i2c_adapter, i2c_board_info))
+    }
+
+    fn try_new(i2c_adapter: &I2cAdapter, i2c_board_info: &I2cBoardInfo) -> Result<Self> {
+        // SAFETY: the kernel guarantees that `i2c_new_client_device()` returns either a valid
+        // pointer or NULL. `from_err_ptr` separates errors. Following `NonNull::new`
+        // checks for NULL.
+        let raw_dev = from_err_ptr(unsafe {
+            bindings::i2c_new_client_device(i2c_adapter.as_raw(), i2c_board_info.as_raw())
+        })?;
+
+        let dev_ptr = NonNull::new(raw_dev).ok_or(ENODEV)?;
+
+        Ok(Self(dev_ptr))
+    }
+}
+
+impl Drop for Registration {
+    fn drop(&mut self) {
+        // SAFETY: `Drop` is only called for a valid `Registration`, which by invariant
+        // always contains a non-null pointer to an `i2c_client`.
+        unsafe { bindings::i2c_unregister_device(self.0.as_ptr()) }
+    }
+}
+
+// SAFETY: A `Registration` of a `struct i2c_client` can be released from any thread.
+unsafe impl Send for Registration {}
+
+// SAFETY: `Registration` offers no interior mutability (no mutation through &self
+// and no mutable access is exposed)
+unsafe impl Sync for Registration {}
-- 
2.43.0

[PATCH v8 3/4] samples: rust: add Rust I2C sample driver

[Igor Korotin]

Add a new `rust_driver_i2c` sample, showing how to create a new
i2c driver using ACPI/OF/Legacy ID tables.

Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
---
 MAINTAINERS                     |  1 +
 samples/rust/Kconfig            | 11 +++++
 samples/rust/Makefile           |  1 +
 samples/rust/rust_driver_i2c.rs | 74 +++++++++++++++++++++++++++++++++
 4 files changed, 87 insertions(+)
 create mode 100644 samples/rust/rust_driver_i2c.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index a8dfde2f5633..8133987c4b54 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11750,6 +11750,7 @@ R:	Daniel Almeida <daniel.almeida@collabora.com>
 L:	rust-for-linux@vger.kernel.org
 S:	Maintained
 F:	rust/kernel/i2c.rs
+F:	samples/rust/rust_driver_i2c.rs
 
 I2C SUBSYSTEM HOST DRIVERS
 M:	Andi Shyti <andi.shyti@kernel.org>
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index c376eb899b7a..181466319588 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_I2C
+	tristate "I2C Driver"
+	depends on I2C=y
+	help
+	  This option builds the Rust I2C driver sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_driver_i2c.
+
+	  If unsure, say N.
+
 config SAMPLE_RUST_DRIVER_PCI
 	tristate "PCI Driver"
 	depends on PCI
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index cf8422f8f219..aec865e2adef 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o
 obj-$(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_PCI)		+= rust_driver_pci.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM)	+= rust_driver_platform.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_USB)		+= rust_driver_usb.o
diff --git a/samples/rust/rust_driver_i2c.rs b/samples/rust/rust_driver_i2c.rs
new file mode 100644
index 000000000000..ecefeca3e22f
--- /dev/null
+++ b/samples/rust/rust_driver_i2c.rs
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust I2C driver sample.
+
+use kernel::{
+    acpi,
+    c_str,
+    device::Core,
+    i2c,
+    of,
+    prelude::*, //
+};
+
+struct SampleDriver;
+
+kernel::acpi_device_table! {
+    ACPI_TABLE,
+    MODULE_ACPI_TABLE,
+    <SampleDriver as i2c::Driver>::IdInfo,
+    [(acpi::DeviceId::new(c_str!("LNUXBEEF")), 0)]
+}
+
+kernel::i2c_device_table! {
+    I2C_TABLE,
+    MODULE_I2C_TABLE,
+    <SampleDriver as i2c::Driver>::IdInfo,
+    [(i2c::DeviceId::new(c_str!("rust_driver_i2c")), 0)]
+}
+
+kernel::of_device_table! {
+    OF_TABLE,
+    MODULE_OF_TABLE,
+    <SampleDriver as i2c::Driver>::IdInfo,
+    [(of::DeviceId::new(c_str!("test,rust_driver_i2c")), 0)]
+}
+
+impl i2c::Driver for SampleDriver {
+    type IdInfo = u32;
+
+    const ACPI_ID_TABLE: Option<acpi::IdTable<Self::IdInfo>> = Some(&ACPI_TABLE);
+    const I2C_ID_TABLE: Option<i2c::IdTable<Self::IdInfo>> = Some(&I2C_TABLE);
+    const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+
+    fn probe(
+        idev: &i2c::I2cClient<Core>,
+        info: Option<&Self::IdInfo>,
+    ) -> impl PinInit<Self, Error> {
+        let dev = idev.as_ref();
+
+        dev_info!(dev, "Probe Rust I2C driver sample.\n");
+
+        if let Some(info) = info {
+            dev_info!(dev, "Probed with info: '{}'.\n", info);
+        }
+
+        Ok(Self)
+    }
+
+    fn shutdown(idev: &i2c::I2cClient<Core>, _this: Pin<&Self>) {
+        dev_info!(idev.as_ref(), "Shutdown Rust I2C driver sample.\n");
+    }
+
+    fn unbind(idev: &i2c::I2cClient<Core>, _this: Pin<&Self>) {
+        dev_info!(idev.as_ref(), "Unbind Rust I2C driver sample.\n");
+    }
+}
+
+kernel::module_i2c_driver! {
+    type: SampleDriver,
+    name: "rust_driver_i2c",
+    authors: ["Igor Korotin"],
+    description: "Rust I2C driver",
+    license: "GPL v2",
+}
-- 
2.43.0

[PATCH v8 4/4] samples: rust: add Rust I2C client registration sample

[Igor Korotin]

Add a new `rust_i2c_client` sample, showing how to create a new
i2c client using `i2c::Registration`

Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
---
 samples/rust/Kconfig            |  12 +++
 samples/rust/Makefile           |   1 +
 samples/rust/rust_i2c_client.rs | 157 ++++++++++++++++++++++++++++++++
 3 files changed, 170 insertions(+)
 create mode 100644 samples/rust/rust_i2c_client.rs

diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index 181466319588..a952220cdff7 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -95,6 +95,18 @@ config SAMPLE_RUST_DRIVER_I2C
 
 	  If unsure, say N.
 
+config SAMPLE_RUST_I2C_CLIENT
+	tristate "Manual I2C Client"
+	depends on I2C && I2C_CHARDEV
+	help
+	  This option builds the Rust I2C client manual creation
+	  sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_i2c_client.
+
+	  If unsure, say N.
+
 config SAMPLE_RUST_DRIVER_PCI
 	tristate "PCI Driver"
 	depends on PCI
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index aec865e2adef..f65885d1d62b 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-$(CONFIG_SAMPLE_RUST_I2C_CLIENT)		+= rust_i2c_client.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI)		+= rust_driver_pci.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM)	+= rust_driver_platform.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_USB)		+= rust_driver_usb.o
diff --git a/samples/rust/rust_i2c_client.rs b/samples/rust/rust_i2c_client.rs
new file mode 100644
index 000000000000..abc6323a5817
--- /dev/null
+++ b/samples/rust/rust_i2c_client.rs
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust I2C client registration sample.
+//!
+//! An I2C client in Rust cannot exist on its own. To register a new I2C client,
+//! it must be bound to a parent device. In this sample driver, a platform device
+//! is used as the parent.
+//!
+
+//! ACPI match table test
+//!
+//! This demonstrates how to test an ACPI-based Rust I2C client registration driver
+//! using QEMU with a custom SSDT.
+//!
+//! Steps:
+//!
+//! 1. **Create an SSDT source file** (`ssdt.dsl`) with the following content:
+//!
+//!     ```asl
+//!     DefinitionBlock ("", "SSDT", 2, "TEST", "VIRTACPI", 0x00000001)
+//!     {
+//!         Scope (\_SB)
+//!         {
+//!             Device (T432)
+//!             {
+//!                 Name (_HID, "LNUXBEEF")  // ACPI hardware ID to match
+//!                 Name (_UID, 1)
+//!                 Name (_STA, 0x0F)        // Device present, enabled
+//!                 Name (_CRS, ResourceTemplate ()
+//!                 {
+//!                     Memory32Fixed (ReadWrite, 0xFED00000, 0x1000)
+//!                 })
+//!             }
+//!         }
+//!     }
+//!     ```
+//!
+//! 2. **Compile the table**:
+//!
+//!     ```sh
+//!     iasl -tc ssdt.dsl
+//!     ```
+//!
+//!     This generates `ssdt.aml`
+//!
+//! 3. **Run QEMU** with the compiled AML file:
+//!
+//!     ```sh
+//!     qemu-system-x86_64 -m 512M \
+//!         -enable-kvm \
+//!         -kernel path/to/bzImage \
+//!         -append "root=/dev/sda console=ttyS0" \
+//!         -hda rootfs.img \
+//!         -serial stdio \
+//!         -acpitable file=ssdt.aml
+//!     ```
+//!
+//!     Requirements:
+//!     - The `rust_driver_platform` must be present either:
+//!         - built directly into the kernel (`bzImage`), or
+//!         - available as a `.ko` file and loadable from `rootfs.img`
+//!
+//! 4. **Verify it worked** by checking `dmesg`:
+//!
+//!     ```
+//!     rust_driver_platform LNUXBEEF:00: Probed with info: '0'.
+//!     ```
+//!
+
+use kernel::{
+    acpi,
+    c_str,
+    device,
+    devres,
+    i2c,
+    of,
+    platform,
+    prelude::*,
+    sync::aref::ARef, //
+};
+
+#[pin_data(PinnedDrop)]
+struct SampleDriver {
+    parent_dev: ARef<platform::Device>,
+    #[pin]
+    idev: devres::Devres<i2c::Registration>,
+}
+
+kernel::of_device_table!(
+    OF_TABLE,
+    MODULE_OF_TABLE,
+    <SampleDriver as platform::Driver>::IdInfo,
+    [(of::DeviceId::new(c_str!("test,rust-device")), ())]
+);
+
+kernel::acpi_device_table!(
+    ACPI_TABLE,
+    MODULE_ACPI_TABLE,
+    <SampleDriver as platform::Driver>::IdInfo,
+    [(acpi::DeviceId::new(c_str!("LNUXBEEF")), ())]
+);
+
+const SAMPLE_I2C_CLIENT_ADDR: u16 = 0x30;
+const SAMPLE_I2C_ADAPTER_INDEX: i32 = 0;
+const BOARD_INFO: i2c::I2cBoardInfo =
+    i2c::I2cBoardInfo::new(c_str!("rust_driver_i2c"), SAMPLE_I2C_CLIENT_ADDR);
+
+impl platform::Driver for SampleDriver {
+    type IdInfo = ();
+    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(
+        pdev: &platform::Device<device::Core>,
+        _info: Option<&Self::IdInfo>,
+    ) -> impl PinInit<Self, Error> {
+        dev_info!(
+            pdev.as_ref(),
+            "Probe Rust I2C Client registration sample.\n"
+        );
+
+        kernel::try_pin_init!( Self {
+            parent_dev: pdev.into(),
+
+            idev <- {
+                let adapter = i2c::I2cAdapter::get(SAMPLE_I2C_ADAPTER_INDEX)?;
+
+                i2c::Registration::new(&adapter, &BOARD_INFO, pdev.as_ref())
+            }
+        })
+    }
+
+    fn unbind(pdev: &platform::Device<device::Core>, _this: Pin<&Self>) {
+        dev_info!(
+            pdev.as_ref(),
+            "Unbind Rust I2C Client registration sample.\n"
+        );
+    }
+}
+
+#[pinned_drop]
+impl PinnedDrop for SampleDriver {
+    fn drop(self: Pin<&mut Self>) {
+        dev_info!(
+            self.parent_dev.as_ref(),
+            "Remove Rust Platform driver for I2C Client registration sample.\n"
+        );
+    }
+}
+
+kernel::module_platform_driver! {
+    type: SampleDriver,
+    name: "rust_device_i2c",
+    authors: ["Danilo Krummrich", "Igor Korotin"],
+    description: "Rust Platform driver",
+    license: "GPL v2",
+}
-- 
2.43.0

Re: [PATCH v8 1/4] rust: i2c: add basic I2C device and driver abstractions

[Markus Probst]

On Sun, 2025-11-16 at 16:21 +0000, Igor Korotin wrote:
> Implement the core abstractions needed for I2C drivers, including:
> 
> * `i2c::Driver` — the trait drivers must implement, including `probe`
> 
> * `i2c::I2cClient` — a safe wrapper around `struct i2c_client`
> 
> * `i2c::Adapter` — implements `driver::RegistrationOps` to hook into the
>   generic `driver::Registration` machinery
> 
> * `i2c::DeviceId` — a `RawDeviceIdIndex` implementation for I2C device IDs
> 
> Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
> ---
>  MAINTAINERS                     |   8 +
>  rust/bindings/bindings_helper.h |   1 +
>  rust/kernel/i2c.rs              | 436 ++++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs              |   2 +
>  4 files changed, 447 insertions(+)
>  create mode 100644 rust/kernel/i2c.rs
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3da2c26a796b..a8dfde2f5633 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11743,6 +11743,14 @@ F:	include/linux/i2c.h
>  F:	include/uapi/linux/i2c-*.h
>  F:	include/uapi/linux/i2c.h
>  
> +I2C SUBSYSTEM [RUST]
> +M:	Igor Korotin <igor.korotin.linux@gmail.com>
> +R:	Danilo Krummrich <dakr@kernel.org>
> +R:	Daniel Almeida <daniel.almeida@collabora.com>
> +L:	rust-for-linux@vger.kernel.org
> +S:	Maintained
> +F:	rust/kernel/i2c.rs
> +
>  I2C SUBSYSTEM HOST DRIVERS
>  M:	Andi Shyti <andi.shyti@kernel.org>
>  L:	linux-i2c@vger.kernel.org
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index a79fd111f886..f92abb578b56 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -58,6 +58,7 @@
>  #include <linux/firmware.h>
>  #include <linux/interrupt.h>
>  #include <linux/fs.h>
> +#include <linux/i2c.h>
>  #include <linux/ioport.h>
>  #include <linux/jiffies.h>
>  #include <linux/jump_label.h>
> diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
> new file mode 100644
> index 000000000000..a5ad8213d9ac
> --- /dev/null
> +++ b/rust/kernel/i2c.rs
> @@ -0,0 +1,436 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! I2C Driver subsystem
> +
> +// I2C Driver abstractions.
> +use crate::{
> +    acpi,
> +    container_of,
> +    device,
> +    device_id::{
> +        RawDeviceId,
> +        RawDeviceIdIndex, //
> +    },
> +    driver,
> +    error::*,
> +    of,
> +    prelude::*,
> +    types::{
> +        AlwaysRefCounted,
> +        Opaque, //
> +    }, //
> +};
> +
> +use core::{
> +    marker::PhantomData,
> +    ptr::NonNull, //
> +};
> +
> +/// An I2C device id table.
> +#[repr(transparent)]
> +#[derive(Clone, Copy)]
> +pub struct DeviceId(bindings::i2c_device_id);
> +
> +impl DeviceId {
> +    const I2C_NAME_SIZE: usize = 20;
> +
> +    /// Create a new device id from an I2C 'id' string.
> +    #[inline(always)]
> +    pub const fn new(id: &'static CStr) -> Self {
> +        build_assert!(
> +            id.len_with_nul() <= Self::I2C_NAME_SIZE,
> +            "ID exceeds 20 bytes"
> +        );
> +        let src = id.as_bytes_with_nul();
> +        // Replace with `bindings::i2c_device_id::default()` once stabilized for `const`.
> +        // SAFETY: FFI type is valid to be zero-initialized.
> +        let mut i2c: bindings::i2c_device_id = pin_init::zeroed();
Clippy throws the error:

error: statement has unnecessary safety comment
  --> rust/kernel/i2c.rs:54:9
   |
54 |         let mut i2c: bindings::i2c_device_id = pin_init::zeroed();
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
help: consider removing the safety comment
  --> rust/kernel/i2c.rs:53:9
   |
53 |         // SAFETY: FFI type is valid to be zero-initialized.
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = help: for further information visit
https://rust-lang.github.io/rust-clippy/rust-1.91.0/index.html#unnecessary_safety_comment
   = note: `-D clippy::unnecessary-safety-comment` implied by `-D
warnings`
   = help: to override `-D warnings` add
`#[allow(clippy::unnecessary_safety_comment)]`

Thanks
- Markus Probst

> +        let mut i = 0;
> +        while i < src.len() {
> +            i2c.name[i] = src[i];
> +            i += 1;
> +        }
> +
> +        Self(i2c)
> +    }
> +}
> +
> +// SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `i2c_device_id` and does not add
> +// additional invariants, so it's safe to transmute to `RawType`.
> +unsafe impl RawDeviceId for DeviceId {
> +    type RawType = bindings::i2c_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::i2c_device_id, driver_data);
> +
> +    fn index(&self) -> usize {
> +        self.0.driver_data
> +    }
> +}
> +
> +/// IdTable type for I2C
> +pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
> +
> +/// Create a I2C `IdTable` with its alias for modpost.
> +#[macro_export]
> +macro_rules! i2c_device_table {
> +    ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
> +        const $table_name: $crate::device_id::IdArray<
> +            $crate::i2c::DeviceId,
> +            $id_info_type,
> +            { $table_data.len() },
> +        > = $crate::device_id::IdArray::new($table_data);
> +
> +        $crate::module_device_table!("i2c", $module_table_name, $table_name);
> +    };
> +}
> +
> +/// An adapter for the registration of I2C drivers.
> +pub struct Adapter<T: Driver>(T);
> +
> +// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
> +// a preceding call to `register` has been successful.
> +unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
> +    type RegType = bindings::i2c_driver;
> +
> +    unsafe fn register(
> +        idrv: &Opaque<Self::RegType>,
> +        name: &'static CStr,
> +        module: &'static ThisModule,
> +    ) -> Result {
> +        build_assert!(
> +            T::ACPI_ID_TABLE.is_some() || T::OF_ID_TABLE.is_some() || T::I2C_ID_TABLE.is_some(),
> +            "At least one of ACPI/OF/Legacy tables must be present when registering an i2c driver"
> +        );
> +
> +        let i2c_table = match T::I2C_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 i2c_client` on initialization.
> +        unsafe {
> +            (*idrv.get()).driver.name = name.as_char_ptr();
> +            (*idrv.get()).probe = Some(Self::probe_callback);
> +            (*idrv.get()).remove = Some(Self::remove_callback);
> +            (*idrv.get()).shutdown = Some(Self::shutdown_callback);
> +            (*idrv.get()).id_table = i2c_table;
> +            (*idrv.get()).driver.of_match_table = of_table;
> +            (*idrv.get()).driver.acpi_match_table = acpi_table;
> +        }
> +
> +        // SAFETY: `idrv` is guaranteed to be a valid `RegType`.
> +        to_result(unsafe { bindings::i2c_register_driver(module.0, idrv.get()) })
> +    }
> +
> +    unsafe fn unregister(idrv: &Opaque<Self::RegType>) {
> +        // SAFETY: `idrv` is guaranteed to be a valid `RegType`.
> +        unsafe { bindings::i2c_del_driver(idrv.get()) }
> +    }
> +}
> +
> +impl<T: Driver + 'static> Adapter<T> {
> +    extern "C" fn probe_callback(idev: *mut bindings::i2c_client) -> kernel::ffi::c_int {
> +        // SAFETY: The I2C bus only ever calls the probe callback with a valid pointer to a
> +        // `struct i2c_client`.
> +        //
> +        // INVARIANT: `idev` is valid for the duration of `probe_callback()`.
> +        let idev = unsafe { &*idev.cast::<I2cClient<device::CoreInternal>>() };
> +
> +        let info =
> +            Self::i2c_id_info(idev).or_else(|| <Self as driver::Adapter>::id_info(idev.as_ref()));
> +
> +        from_result(|| {
> +            let data = T::probe(idev, info);
> +
> +            idev.as_ref().set_drvdata(data)?;
> +            Ok(0)
> +        })
> +    }
> +
> +    extern "C" fn remove_callback(idev: *mut bindings::i2c_client) {
> +        // SAFETY: `idev` is a valid pointer to a `struct i2c_client`.
> +        let idev = unsafe { &*idev.cast::<I2cClient<device::CoreInternal>>() };
> +
> +        // SAFETY: `remove_callback` is only ever called after a successful call to
> +        // `probe_callback`, hence it's guaranteed that `I2cClient::set_drvdata()` has been called
> +        // and stored a `Pin<KBox<T>>`.
> +        let data = unsafe { idev.as_ref().drvdata_obtain::<T>() };
> +
> +        T::unbind(idev, data.as_ref());
> +    }
> +
> +    extern "C" fn shutdown_callback(idev: *mut bindings::i2c_client) {
> +        // SAFETY: `shutdown_callback` is only ever called for a valid `idev`
> +        let idev = unsafe { &*idev.cast::<I2cClient<device::CoreInternal>>() };
> +
> +        // SAFETY: `shutdown_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<T>>`.
> +        let data = unsafe { idev.as_ref().drvdata_obtain::<T>() };
> +
> +        T::shutdown(idev, data.as_ref());
> +    }
> +
> +    /// The [`i2c::IdTable`] of the corresponding driver.
> +    fn i2c_id_table() -> Option<IdTable<<Self as driver::Adapter>::IdInfo>> {
> +        T::I2C_ID_TABLE
> +    }
> +
> +    /// Returns the driver's private data from the matching entry in the [`i2c::IdTable`], if any.
> +    ///
> +    /// If this returns `None`, it means there is no match with an entry in the [`i2c::IdTable`].
> +    fn i2c_id_info(dev: &I2cClient) -> Option<&'static <Self as driver::Adapter>::IdInfo> {
> +        let table = Self::i2c_id_table()?;
> +
> +        // SAFETY:
> +        // - `table` has static lifetime, hence it's valid for reads
> +        // - `dev` is guaranteed to be valid while it's alive, and so is `dev.as_raw()`.
> +        let raw_id = unsafe { bindings::i2c_match_id(table.as_ptr(), dev.as_raw()) };
> +
> +        if raw_id.is_null() {
> +            return None;
> +        }
> +
> +        // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of `struct i2c_device_id` and
> +        // does not add additional invariants, so it's safe to transmute.
> +        let id = unsafe { &*raw_id.cast::<DeviceId>() };
> +
> +        Some(table.info(<DeviceId as RawDeviceIdIndex>::index(id)))
> +    }
> +}
> +
> +impl<T: Driver + 'static> 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 i2c driver.
> +///
> +/// # Examples
> +///
> +/// ```ignore
> +/// kernel::module_i2c_driver! {
> +///     type: MyDriver,
> +///     name: "Module name",
> +///     authors: ["Author name"],
> +///     description: "Description",
> +///     license: "GPL v2",
> +/// }
> +/// ```
> +#[macro_export]
> +macro_rules! module_i2c_driver {
> +    ($($f:tt)*) => {
> +        $crate::module_driver!(<T>, $crate::i2c::Adapter<T>, { $($f)* });
> +    };
> +}
> +
> +/// The i2c driver trait.
> +///
> +/// Drivers must implement this trait in order to get a i2c driver registered.
> +///
> +/// # Example
> +///
> +///```
> +/// # use kernel::{acpi, bindings, c_str, device::Core, i2c, of};
> +///
> +/// struct MyDriver;
> +///
> +/// kernel::acpi_device_table!(
> +///     ACPI_TABLE,
> +///     MODULE_ACPI_TABLE,
> +///     <MyDriver as i2c::Driver>::IdInfo,
> +///     [
> +///         (acpi::DeviceId::new(c_str!("LNUXBEEF")), ())
> +///     ]
> +/// );
> +///
> +/// kernel::i2c_device_table!(
> +///     I2C_TABLE,
> +///     MODULE_I2C_TABLE,
> +///     <MyDriver as i2c::Driver>::IdInfo,
> +///     [
> +///          (i2c::DeviceId::new(c_str!("rust_driver_i2c")), ())
> +///     ]
> +/// );
> +///
> +/// kernel::of_device_table!(
> +///     OF_TABLE,
> +///     MODULE_OF_TABLE,
> +///     <MyDriver as i2c::Driver>::IdInfo,
> +///     [
> +///         (of::DeviceId::new(c_str!("test,device")), ())
> +///     ]
> +/// );
> +///
> +/// impl i2c::Driver for MyDriver {
> +///     type IdInfo = ();
> +///     const I2C_ID_TABLE: Option<i2c::IdTable<Self::IdInfo>> = Some(&I2C_TABLE);
> +///     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(
> +///         _idev: &i2c::I2cClient<Core>,
> +///         _id_info: Option<&Self::IdInfo>,
> +///     ) -> impl PinInit<Self, Error> {
> +///         Err(ENODEV)
> +///     }
> +///
> +///     fn shutdown(_idev: &i2c::I2cClient<Core>, this: Pin<&Self>) {
> +///     }
> +/// }
> +///```
> +pub trait Driver: Send {
> +    /// 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 table of device ids supported by the driver.
> +    const I2C_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;
> +
> +    /// I2C driver probe.
> +    ///
> +    /// Called when a new i2c client is added or discovered.
> +    /// Implementers should attempt to initialize the client here.
> +    fn probe(
> +        dev: &I2cClient<device::Core>,
> +        id_info: Option<&Self::IdInfo>,
> +    ) -> impl PinInit<Self, Error>;
> +
> +    /// I2C driver shutdown.
> +    ///
> +    /// Called by the kernel during system reboot or power-off to allow the [`Driver`] to bring the
> +    /// [`Device`] 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 `Self::drop`.
> +    fn shutdown(dev: &I2cClient<device::Core>, this: Pin<&Self>) {
> +        let _ = (dev, this);
> +    }
> +
> +    /// I2C 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, drivers may try to perform I/O
> +    /// operations to gracefully tear down the device.
> +    ///
> +    /// Otherwise, release operations for driver resources should be performed in `Self::drop`.
> +    fn unbind(dev: &I2cClient<device::Core>, this: Pin<&Self>) {
> +        let _ = (dev, this);
> +    }
> +}
> +
> +/// The i2c client representation.
> +///
> +/// This structure represents the Rust abstraction for a C `struct i2c_client`. The
> +/// implementation abstracts the usage of an existing C `struct i2c_client` that
> +/// gets passed from the C side
> +///
> +/// # Invariants
> +///
> +/// A [`I2cClient`] instance represents a valid `struct i2c_client` created by the C portion of
> +/// the kernel.
> +#[repr(transparent)]
> +pub struct I2cClient<Ctx: device::DeviceContext = device::Normal>(
> +    Opaque<bindings::i2c_client>,
> +    PhantomData<Ctx>,
> +);
> +
> +impl<Ctx: device::DeviceContext> I2cClient<Ctx> {
> +    fn as_raw(&self) -> *mut bindings::i2c_client {
> +        self.0.get()
> +    }
> +}
> +
> +// SAFETY: `I2cClient` is a transparent wrapper of a type that doesn't depend on
> +// `I2cClient`'s generic argument.
> +kernel::impl_device_context_deref!(unsafe { I2cClient });
> +kernel::impl_device_context_into_aref!(I2cClient);
> +
> +// SAFETY: Instances of `I2cClient` are always reference-counted.
> +unsafe impl AlwaysRefCounted for I2cClient {
> +    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 I2cClient<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 i2c_client`.
> +        let dev = unsafe { &raw mut (*raw).dev };
> +
> +        // SAFETY: `dev` points to a valid `struct device`.
> +        unsafe { device::Device::from_raw(dev) }
> +    }
> +}
> +
> +impl<Ctx: device::DeviceContext> TryFrom<&device::Device<Ctx>> for &I2cClient<Ctx> {
> +    type Error = kernel::error::Error;
> +
> +    fn try_from(dev: &device::Device<Ctx>) -> Result<Self, Self::Error> {
> +        // SAFETY: By the type invariant of `Device`, `dev.as_raw()` is a valid pointer to a
> +        // `struct device`.
> +        if unsafe { bindings::i2c_verify_client(dev.as_raw()).is_null() } {
> +            return Err(EINVAL);
> +        }
> +
> +        // SAFETY: We've just verified that the type of `dev` equals to
> +        // `bindings::i2c_client_type`, hence `dev` must be embedded in a valid
> +        // `struct i2c_client` as guaranteed by the corresponding C code.
> +        let idev = unsafe { container_of!(dev.as_raw(), bindings::i2c_client, dev) };
> +
> +        // SAFETY: `idev` is a valid pointer to a `struct i2c_client`.
> +        Ok(unsafe { &*idev.cast() })
> +    }
> +}
> +
> +// SAFETY: A `I2cClient` is always reference-counted and can be released from any thread.
> +unsafe impl Send for I2cClient {}
> +
> +// SAFETY: `I2cClient` can be shared among threads because all methods of `I2cClient`
> +// (i.e. `I2cClient<Normal>) are thread safe.
> +unsafe impl Sync for I2cClient {}
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 3dd7bebe7888..8c0070a8029e 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -94,6 +94,8 @@
>  pub mod firmware;
>  pub mod fmt;
>  pub mod fs;
> +#[cfg(CONFIG_I2C = "y")]
> +pub mod i2c;
>  pub mod id_pool;
>  pub mod init;
>  pub mod io;

Re: [PATCH v8 2/4] rust: i2c: add manual I2C device creation abstractions

[Markus Probst]

On Sun, 2025-11-16 at 16:21 +0000, Igor Korotin wrote:
> In addition to the basic I2C device support, add rust abstractions
> upon `i2c_new_client_device`/`i2c_unregister_device` C functions.
> 
> Implement the core abstractions needed for manual creation/deletion
> of I2C devices, including:
> 
>  * `i2c::Registration` — a NonNull pointer created by the function
>                           `i2c_new_client_device`
> 
>  * `i2c::I2cAdapter` — a ref counted wrapper around `struct i2c_adapter`
> 
>  * `i2c::I2cBoardInfo` — a safe wrapper around `struct i2c_board_info`
> 
> Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
> ---
>  rust/kernel/i2c.rs | 155 ++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 154 insertions(+), 1 deletion(-)
> 
> diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
> index a5ad8213d9ac..3695b4adf436 100644
> --- a/rust/kernel/i2c.rs
> +++ b/rust/kernel/i2c.rs
> @@ -11,6 +11,7 @@
>          RawDeviceId,
>          RawDeviceIdIndex, //
>      },
> +    devres::Devres,
>      driver,
>      error::*,
>      of,
> @@ -23,9 +24,14 @@
>  
>  use core::{
>      marker::PhantomData,
> -    ptr::NonNull, //
> +    ptr::{
> +        from_ref,
> +        NonNull, //
> +    }, //
>  };
>  
> +use kernel::types::ARef;
> +
>  /// An I2C device id table.
>  #[repr(transparent)]
>  #[derive(Clone, Copy)]
> @@ -356,6 +362,102 @@ fn unbind(dev: &I2cClient<device::Core>, this: Pin<&Self>) {
>      }
>  }
>  
> +/// The i2c adapter representation.
> +///
> +/// This structure represents the Rust abstraction for a C `struct i2c_adapter`. The
> +/// implementation abstracts the usage of an existing C `struct i2c_adapter` that
> +/// gets passed from the C side
> +///
> +/// # Invariants
> +///
> +/// A [`I2cAdapter`] instance represents a valid `struct i2c_adapter` created by the C portion of
> +/// the kernel.
> +#[repr(transparent)]
> +pub struct I2cAdapter<Ctx: device::DeviceContext = device::Normal>(
> +    Opaque<bindings::i2c_adapter>,
> +    PhantomData<Ctx>,
> +);
> +
> +impl<Ctx: device::DeviceContext> I2cAdapter<Ctx> {
> +    fn as_raw(&self) -> *mut bindings::i2c_adapter {
> +        self.0.get()
> +    }
> +}
> +
> +impl I2cAdapter {
> +    /// Returns the I2C Adapter index.
> +    #[inline]
> +    pub fn index(&self) -> i32 {
> +        // SAFETY: `self.as_raw` is a valid pointer to a `struct i2c_adapter`.
> +        unsafe { (*self.as_raw()).nr }
> +    }
> +
> +    /// Gets pointer to an `i2c_adapter` by index.
> +    pub fn get(index: i32) -> Result<ARef<Self>> {
> +        // SAFETY: `index` must refer to a valid I2C adapter; the kernel
> +        // guarantees that `i2c_get_adapter(index)` returns either a valid
> +        // pointer or NULL. `NonNull::new` guarantees the correct check.
> +        let adapter = NonNull::new(unsafe { bindings::i2c_get_adapter(index) }).ok_or(ENODEV)?;
> +
> +        // SAFETY: `adapter` is non-null and points to a live `i2c_adapter`.
> +        // `I2cAdapter` is #[repr(transparent)], so this cast is valid.
> +        Ok(unsafe { (&*adapter.as_ptr().cast::<I2cAdapter<device::Normal>>()).into() })
> +    }
> +}
> +
> +// SAFETY: `I2cAdapter` is a transparent wrapper of a type that doesn't depend on
> +// `I2cAdapter`'s generic argument.
> +kernel::impl_device_context_deref!(unsafe { I2cAdapter });
> +kernel::impl_device_context_into_aref!(I2cAdapter);
> +
> +// SAFETY: Instances of `I2cAdapter` are always reference-counted.
> +unsafe impl crate::types::AlwaysRefCounted for I2cAdapter {
> +    fn inc_ref(&self) {
> +        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
> +        unsafe { bindings::i2c_get_adapter(self.index()) };
> +    }
> +
> +    unsafe fn dec_ref(obj: NonNull<Self>) {
> +        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
> +        unsafe { bindings::i2c_put_adapter(obj.as_ref().as_raw()) }
> +    }
> +}
> +
> +/// The i2c board info representation
> +///
> +/// This structure represents the Rust abstraction for a C `struct i2c_board_info` structure,
> +/// which is used for manual I2C client creation.
> +#[repr(transparent)]
> +pub struct I2cBoardInfo(bindings::i2c_board_info);
> +
> +impl I2cBoardInfo {
> +    const I2C_TYPE_SIZE: usize = 20;
> +    /// Create a new [`I2cBoardInfo`] for a kernel driver.
> +    #[inline(always)]
> +    pub const fn new(type_: &'static CStr, addr: u16) -> Self {
> +        build_assert!(
> +            type_.len_with_nul() <= Self::I2C_TYPE_SIZE,
> +            "Type exceeds 20 bytes"
> +        );
> +        let src = type_.as_bytes_with_nul();
> +        // Replace with `bindings::i2c_board_info::default()` once stabilized for `const`.
> +        // SAFETY: FFI type is valid to be zero-initialized.
> +        let mut i2c_board_info: bindings::i2c_board_info = pin_init::zeroed();
Same clippy error here:

error: statement has unnecessary safety comment
   --> rust/kernel/i2c.rs:446:9
    |
446 |         let mut i2c_board_info: bindings::i2c_board_info =
pin_init::zeroed();
    |        
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
help: consider removing the safety comment
   --> rust/kernel/i2c.rs:445:9
    |
445 |         // SAFETY: FFI type is valid to be zero-initialized.
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: for further information visit
https://rust-lang.github.io/rust-clippy/rust-1.91.0/index.html#unnecessary_safety_comment

Thanks
- Markus Probst

> +        let mut i: usize = 0;
> +        while i < src.len() {
> +            i2c_board_info.type_[i] = src[i];
> +            i += 1;
> +        }
> +
> +        i2c_board_info.addr = addr;
> +        Self(i2c_board_info)
> +    }
> +
> +    fn as_raw(&self) -> *const bindings::i2c_board_info {
> +        from_ref(&self.0)
> +    }
> +}
> +
>  /// The i2c client representation.
>  ///
>  /// This structure represents the Rust abstraction for a C `struct i2c_client`. The
> @@ -434,3 +536,54 @@ unsafe impl Send for I2cClient {}
>  // SAFETY: `I2cClient` can be shared among threads because all methods of `I2cClient`
>  // (i.e. `I2cClient<Normal>) are thread safe.
>  unsafe impl Sync for I2cClient {}
> +
> +/// The registration of an i2c client device.
> +///
> +/// This type represents the registration of a [`struct i2c_client`]. When an instance of this
> +/// type is dropped, its respective i2c client device will be unregistered from the system.
> +///
> +/// # Invariants
> +///
> +/// `self.0` always holds a valid pointer to an initialized and registered
> +/// [`struct i2c_client`].
> +#[repr(transparent)]
> +pub struct Registration(NonNull<bindings::i2c_client>);
> +
> +impl Registration {
> +    /// The C `i2c_new_client_device` function wrapper for manual I2C client creation.
> +    pub fn new<'a>(
> +        i2c_adapter: &I2cAdapter,
> +        i2c_board_info: &I2cBoardInfo,
> +        parent_dev: &'a device::Device<device::Bound>,
> +    ) -> impl PinInit<Devres<Self>, Error> + 'a {
> +        Devres::new(parent_dev, Self::try_new(i2c_adapter, i2c_board_info))
> +    }
> +
> +    fn try_new(i2c_adapter: &I2cAdapter, i2c_board_info: &I2cBoardInfo) -> Result<Self> {
> +        // SAFETY: the kernel guarantees that `i2c_new_client_device()` returns either a valid
> +        // pointer or NULL. `from_err_ptr` separates errors. Following `NonNull::new`
> +        // checks for NULL.
> +        let raw_dev = from_err_ptr(unsafe {
> +            bindings::i2c_new_client_device(i2c_adapter.as_raw(), i2c_board_info.as_raw())
> +        })?;
> +
> +        let dev_ptr = NonNull::new(raw_dev).ok_or(ENODEV)?;
> +
> +        Ok(Self(dev_ptr))
> +    }
> +}
> +
> +impl Drop for Registration {
> +    fn drop(&mut self) {
> +        // SAFETY: `Drop` is only called for a valid `Registration`, which by invariant
> +        // always contains a non-null pointer to an `i2c_client`.
> +        unsafe { bindings::i2c_unregister_device(self.0.as_ptr()) }
> +    }
> +}
> +
> +// SAFETY: A `Registration` of a `struct i2c_client` can be released from any thread.
> +unsafe impl Send for Registration {}
> +
> +// SAFETY: `Registration` offers no interior mutability (no mutation through &self
> +// and no mutable access is exposed)
> +unsafe impl Sync for Registration {}

Re: [PATCH v8 0/4] rust: i2c: Add basic I2C driver abstractions

[Markus Probst]

add me to cc please.

My led driver currently relies on the i2c bindings.

Thanks
- Markus Probst

[1]
https://lore.kernel.org/rust-for-linux/20251008181027.662616-1-markus.probst@posteo.de/

On Sun, 2025-11-16 at 16:21 +0000, Igor Korotin wrote:
> This patch series lays the groundwork for writing Linux I2C drivers in 
> Rust by:
> 
>  1. Core abstractions 
>     Introduce `i2c::I2cClient`, `i2c::I2cAdapter`, `i2c::Driver` and 
>     built on the existing `struct i2c_client`, `struct i2c_adapter` 
>     and `struct i2c_driver`, with safe Rust wrappers around probe, 
>     transfer, and teardown logic.
> 
>  2. Manual device creation  
>     Provide an API to register an I2C device at runtime from Rust using
>     `I2cBoardInfo` and `I2cAdapter`, including automatic cleanup when 
>     the driver unloads.
> 
>  3. Sample I2C driver (legacy table, OF & ACPI)  
>     Add `rust_driver_i2c`, a sample that:
>       - binds to an I2C client via: 
>         - legacy I2C-ID table, 
>         - Open Firmware (device-tree) compatible strings, or
>         - ACPI IDs.
>  4. Sample I2C client registration (OF & ACPI)
>     Add `rust_i2c_client`, a sample that:
>       - binds to a platform parent device using OF/ACPI table
>       - registers new I2C client bound to the parent platform device
>         using `i2c::Registration::new()`
>       - destroyes the I2C client device on exit.
> 
> Together, these four patches:
> 
> - Establish the essential Rust traits and types for I2C drivers.
> - Enable driver binding via legacy ID table, device-tree (OF), or ACPI
> - Enable manual device creation at runtime.
> - Ship a samples showing typical usage 
> 
> Igor Korotin (4):
>   rust: i2c: add basic I2C device and driver abstractions
>   rust: i2c: add manual I2C device creation abstractions
>   samples: rust: add Rust I2C sample driver
>   samples: rust: add Rust I2C client registration sample
> 
> Changelog
> ---------
> v8:
>  - Rebase commits on top of [1]
>  - Applied kernel vertical style [2] 
>  - Replace core::mem::zeroed() with pin_init::zeroed()
>  - Rename `I2cAdapter::get_nr` to `I2cAdapter::index`
>  - fixed some minor format issues
>  - Link to v7: [3]
> 
>  [1] https://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git/log/?h=driver-core-next
>  [2] https://docs.kernel.org/rust/coding-guidelines.html#imports
>  [3] https://lore.kernel.org/rust-for-linux/20251110112437.50405-1-igor.korotin.linux@gmail.com/
> 
> v7:
>  - Rebase and update `i2c::Driver::probe` function based on patch 
>    series [1].
>  - use `i2c::Driver::unbind` instead of `drop` in 
>    `i2c::Adapter::remove_callback`
>  - Implement and use `i2c::Driver::unbind` for I2C SampleDriver
>    instead of Drop.
>  - `i2c::Registration::new` requires a parent device to which a new
>    I2C client will be bound. 
>  - `i2c::Registration::new` returns `impl PinInit<Devres<Self>, Error>`
>  - The existing rust_driver_i2c sample has been split into two:
>    `rust_driver_i2c`, which demonstrates the implementation of an I2C 
>    driver, and `rust_i2c_client`, which demonstrates registering a new 
>    I2C client bound to a parent platform device.
>  - Link to v6: [2]
> 
>  [1] https://lore.kernel.org/all/20251016125544.15559-1-dakr@kernel.org/
>  [2] https://lore.kernel.org/rust-for-linux/20251005102226.41876-1-igor.korotin.linux@gmail.com/ 
> 
> v6:
>  - Add implementation of unbind for `i2c::Driver` trait;
>  - Add argument `Pin<&Self>` to `i2c::Driver::shutdown` method; 
>  - Adjust usage of `i2c::Driver::shutdown` in 
>    `i2c::Adapter::shutdown_callback` in `i2c::Driver` trait code 
>    example and in rust_driver_i2c code;
>  - Remove dummy AsRef implementation for I2cAdapter. Adjust code 
>    in rust_driver_i2c;
>  - Add `i2c::I2cAdapter::get_nr` method that returns I2cAdapter index;
>  - Optimize unsafe sections in inc_ref/dec_ref in AlwaysRefCounted 
>    for I2cAdapter implementation;
>  - Remove unnecessary Drop implementation for I2cAdapter, because 
>    I2cAdapter is always a reference;
>  - Remove unnecessary type definition `Ops<T>` in rust_driver_i2c
>  - Simplify call of `i2c::I2cAdapter::get` in `try_pin_init!` macro 
>    for rust_driver_i2c
>  - Link to v5: https://lore.kernel.org/rust-for-linux/20250911154717.96637-1-igor.korotin.linux@gmail.com/ 
> v5:
>  - Rename missed pdev variables to idev (thanks to Daniel).
>  - Import `crate::device_id::RawDeviceIdIndex` and 
>    `crate::types::AlwaysRefCounted` in i2c.rs.
>  - Switch dev_dbg to dev_info in the sample I2C driver messages.
>  - Make `I2cAdapter::get()` return `ARef<I2cAdapter>` instead of 
>    `&I2cAdapter`.
>  - Remove `TryFrom<device::Device<Ctx>> for I2cAdapter<Ctx>` (unused; 
>    to be reintroduced in a later I2C series).
>  - Remove `AsRef<device::Device<Ctx>> for I2cAdapter<Ctx>` (unused; 
>    to be reintroduced in a later I2C series).
>  - Add `AsRef<I2cAdapter> for I2cAdapter<Ctx>`.
>  - Use i2c_get/put_adapter instead of get/put_device for 
>    `AlwaysRefCounted<I2cAdapter>`.
>  - Update safety comment for `unsafe impl Sync for Registration {}`.
>  - Tweak comment for `I2cBoardInfo::new`.
>  - Adjust build-time assertion message in `Adapter::register`.
>  - Link to v4: https://lore.kernel.org/rust-for-linux/20250820151427.1812482-1-igor.korotin.linux@gmail.com/ 
> v4:
>  - Renamed `i2c::I2cAdapterRef` to `i2c::I2cAdapter`.
>  - Renamed `i2c::Device` to `i2c::I2cClient` for consistency with 
>    `i2c::I2cAdapter` and to avoid confusion with `i2c::Adapter`
>  - Reworked `i2c::I2cAdapter` to be an Opaque around `i2c_adapter` struct
>  - Implemented AlwaysRefCounted trait for `i2c::I2cAdapter`. 
>  - Fixed numerous comment mistakes and typos all over the code, thanks 
>    to Danilo and Daniel
>  - Got rid of all unwrap() use-cases in i2c.rs and rust_driver_i2c.rs.
>    This covers 0-day kernel panic <202508071027.8981cbd4-lkp@intel.com>
>  - Removed unnecessary casts.
>  - Replaced all addr_of_mut! macros to &raw mut.
>  - In `i2c::Adapter::register` method build assert if all ID tables are 
>    None.
>  - Renamed all pdrv and pdev instances to idrv and idev respectivly 
>  - Implemented an ealry return in `i2c::Adapter::i2c_id_info`
>  - Added all missing Safety comments. 
>  - Removed `unsafe impl<Ctx: device::DeviceContext> crate::types::AlwaysRefCounted for Device<Ctx>` 
>    implementation which came to v3 from v2 by mistake.
>  - Added more details regarding i2c-stub driver usage in rust_driver_i2c
>    comment.
>  - Changed `i2c::I2cAdapter::get` return type from `Option<Self>` to 
>    `Result<&'static Self>`.
>  - Added Daniel Almeida as a reviewer to the "I2C Subsystem [RUST]" entry 
>    in MAINTAINERS, per his offer.
>  - Link to v3: https://lore.kernel.org/rust-for-linux/20250801153742.13472-1-igor.korotin.linux@gmail.com/
> v3: 
>  - removed unnecessary i2c_get_clientdata and i2c_set_clientdata rust 
>    helpers. Using generic accessors implemented in [1] instead.
>  - Reimplemented i2c::DeviceId based on changes in [2].
>  - Using from_result in i2c::Adapter::probe_callback
>  - Using explicit drop() for i2c client private data in 
>    `i2c::Adapter::remove_callback`
>  - replaced device::Device::as_ref() with device::Device::from_raw in 
>    `i2c::Device::as_ref()`. It is renamed in device::Device.
>  - Build Rust I2C only if I2C is built-in
>  - Reimplement overcomplicated trait i2c::DeviceOwned the same way it is 
>    implemented in auxiliary [3].
>  - Merge rust_device_i2c and rust_driver_i2c samples. Resulting 
>    rust_driver_i2c creates pined i2c_client using i2c::Registration::new 
>    and probes newly created i2c_client.
>  - Created a new entry in MAINTAINERS file containing i2c.rs and 
>    rust_driver_i2c.rs in it.
>  - Link to v2: [4] 
> 
>  [1] https://lore.kernel.org/lkml/20250621195118.124245-3-dakr@kernel.org/
>  [2] https://lore.kernel.org/rust-for-linux/20250711040947.1252162-1-fujita.tomonori@gmail.com/
>  [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/rust/kernel/auxiliary.rs?h=v6.16-rc4#n299
>  [4] https://lore.kernel.org/rust-for-linux/20250704153332.1193214-1-igor.korotin.linux@gmail.com/ 
> 
> v2:
>  - Merged separated ACPI support patches since ACPI-table support is 
>    merged into driver-core-next.
>  - Added I2cAdapterRef and I2cBoardInfo abstractions 
>  - Added DeviceState generic parameter which is used for `i2c::Device`
>    as a sign if the device is created manually
>  - Added `DeviceOwned` abstraction which is a safe reference to a 
>    manually created `i2c::Device<Ctx, state::Owned>`. 
>  - Added Rust manual I2C device creation sample
>  - Link to v1: https://lore.kernel.org/rust-for-linux/20250626174623.904917-1-igor.korotin.linux@gmail.com/
> 
>  MAINTAINERS                     |   9 +
>  rust/bindings/bindings_helper.h |   1 +
>  rust/kernel/i2c.rs              | 589 ++++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs              |   2 +
>  samples/rust/Kconfig            |  23 ++
>  samples/rust/Makefile           |   2 +
>  samples/rust/rust_driver_i2c.rs |  74 ++++
>  samples/rust/rust_i2c_client.rs | 157 +++++++++
>  8 files changed, 857 insertions(+)
>  create mode 100644 rust/kernel/i2c.rs
>  create mode 100644 samples/rust/rust_driver_i2c.rs
>  create mode 100644 samples/rust/rust_i2c_client.rs
> 
> 
> base-commit: ededb7bcdfdbcfbb7af93e3a543165a9553e1683

Re: [PATCH v8 0/4] rust: i2c: Add basic I2C driver abstractions

[Danilo Krummrich]

(Cc: Markus)

On Mon Nov 17, 2025 at 3:21 AM AEDT, Igor Korotin wrote:

Applied to driver-core-testing, thanks!

> Igor Korotin (4):
>   rust: i2c: add basic I2C device and driver abstractions

    [ Remove unnecessary safety comment; fix rustdoc `Device` -> `I2cClient`.
      - Danilo ]

>   rust: i2c: add manual I2C device creation abstractions

    [ Remove unnecessary safety comment. - Danilo ]

>   samples: rust: add Rust I2C sample driver
>   samples: rust: add Rust I2C client registration sample

    [ * Remove dependency to I2C_CHARDEV, depend on I2C=y.
      * Remove unnecessary impl Drop for SampleDriver.
      * Rename i2c::Registration, import Devres.
      * Fixup module description.
      * Add new source file to MAINTAINERS.
      - Danilo ]

Re: [PATCH v8 0/4] rust: i2c: Add basic I2C driver abstractions

[Igor Korotin]

Hello Danilo

On 11/17/2025 9:40 PM, Danilo Krummrich wrote:
> (Cc: Markus)
> 
> On Mon Nov 17, 2025 at 3:21 AM AEDT, Igor Korotin wrote:
> 
> Applied to driver-core-testing, thanks!
> 
>> Igor Korotin (4):
>>    rust: i2c: add basic I2C device and driver abstractions
> 
>      [ Remove unnecessary safety comment; fix rustdoc `Device` -> `I2cClient`.
>        - Danilo ]
> 
>>    rust: i2c: add manual I2C device creation abstractions
> 
>      [ Remove unnecessary safety comment. - Danilo ]
> 
>>    samples: rust: add Rust I2C sample driver
>>    samples: rust: add Rust I2C client registration sample
> 
>      [ * Remove dependency to I2C_CHARDEV, depend on I2C=y.
>        * Remove unnecessary impl Drop for SampleDriver.
>        * Rename i2c::Registration, import Devres.
>        * Fixup module description.
>        * Add new source file to MAINTAINERS.
>        - Danilo ]

Thanks a lot for the review and all the fixes of yours.

Cheers
Igor

Re: [PATCH v8 0/4] rust: i2c: Add basic I2C driver abstractions

[Igor Korotin]

Hello Markus

On 11/17/2025 4:15 PM, Markus Probst wrote:
> add me to cc please.
> 
> My led driver currently relies on the i2c bindings.
> 
> Thanks
> - Markus Probst

Sure, no problem

Thanks
Igor