[PATCH v5 0/3] rust: i2c: Add basic I2C driver abstractions

[PATCH v5 0/3] 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 driver (legacy table, OF & ACPI)  
    Add `rust_driver_i2c`, a sample that:
      - creates an I2C client device using `i2c::Registration::new()`
      - binds to an I2C client via: 
        - legacy I2C-ID table, 
        - Open Firmware (device-tree) compatible strings, or
        - ACPI IDs.
      - destroyes the I2C client device on exit.

Together, these three 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 (3):
  rust: i2c: add basic I2C device and driver abstractions
  rust: i2c: add manual I2C device creation abstractions
  samples: rust: add Rust I2C sample driver

Changelog
---------
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              | 547 ++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |   2 +
 samples/rust/Kconfig            |  11 +
 samples/rust/Makefile           |   1 +
 samples/rust/rust_driver_i2c.rs | 128 ++++++++
 7 files changed, 699 insertions(+)
 create mode 100644 rust/kernel/i2c.rs
 create mode 100644 samples/rust/rust_driver_i2c.rs


base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
-- 
2.43.0

[PATCH v5 1/3] 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              | 396 ++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |   2 +
 4 files changed, 407 insertions(+)
 create mode 100644 rust/kernel/i2c.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index fe168477caa4..c44c7ac317b1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11516,6 +11516,14 @@ 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 84d60635e8a9..81796d5e16e8 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -53,6 +53,7 @@
 #include <linux/file.h>
 #include <linux/firmware.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..c17665cd5662
--- /dev/null
+++ b/rust/kernel/i2c.rs
@@ -0,0 +1,396 @@
+// 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::acpi_device_id::default()` once stabilized for `const`.
+        // SAFETY: FFI type is valid to be zero-initialized.
+        let mut i2c: bindings::i2c_device_id = unsafe { core::mem::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>>`.
+        drop(unsafe { idev.as_ref().drvdata_obtain::<Pin<KBox<T>>>() });
+    }
+
+    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::Core>>() };
+
+        T::shutdown(idev);
+    }
+
+    /// 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>,
+///     ) -> Result<Pin<KBox<Self>>> {
+///         Err(ENODEV)
+///     }
+///
+///     fn shutdown(_idev: &i2c::I2cClient<Core>) {
+///     }
+/// }
+///```
+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>,
+    ) -> Result<Pin<KBox<Self>>>;
+
+    /// I2C driver shutdown
+    ///
+    /// Called when
+    fn shutdown(dev: &I2cClient<device::Core>) {
+        let _ = dev;
+    }
+}
+
+/// 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 ed53169e795c..a5e97a9b1546 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -89,6 +89,8 @@
 pub mod firmware;
 pub mod fmt;
 pub mod fs;
+#[cfg(CONFIG_I2C = "y")]
+pub mod i2c;
 pub mod init;
 pub mod io;
 pub mod ioctl;
-- 
2.43.0

[PATCH v5 2/3] 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 | 153 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 152 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index c17665cd5662..97865a9d8fea 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -13,7 +13,12 @@
     types::{AlwaysRefCounted, Opaque},
 };
 
-use core::{marker::PhantomData, ptr::NonNull};
+use core::{
+    marker::PhantomData,
+    ptr::{from_ref, NonNull},
+};
+
+use kernel::types::ARef;
 
 /// An I2C device id table.
 #[repr(transparent)]
@@ -316,6 +321,110 @@ fn shutdown(dev: &I2cClient<device::Core>) {
     }
 }
 
+/// 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 {
+    /// 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() })
+    }
+}
+
+impl<Ctx: device::DeviceContext> Drop for I2cAdapter<Ctx> {
+    fn drop(&mut self) {
+        // SAFETY: This `I2cAdapter` was obtained from `i2c_get_adapter`,
+        // and calling `i2c_put_adapter` exactly once will correctly release
+        // the reference count in the I2C core. It is safe to call from any context
+        unsafe { bindings::i2c_put_adapter(self.as_raw()) }
+    }
+}
+
+// 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.as_raw()).nr) };
+    }
+
+    unsafe fn dec_ref(obj: NonNull<Self>) {
+        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+        unsafe { bindings::i2c_put_adapter(&raw mut (*obj.as_ref().as_raw())) }
+    }
+}
+
+impl<Ctx: device::DeviceContext> AsRef<I2cAdapter<Ctx>> for I2cAdapter<Ctx> {
+    fn as_ref(&self) -> &I2cAdapter<Ctx> {
+        &self
+    }
+}
+
+/// 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::acpi_device_id::default()` once stabilized for `const`.
+        // SAFETY: FFI type is valid to be zero-initialized.
+        let mut i2c_board_info: bindings::i2c_board_info = unsafe { core::mem::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
@@ -394,3 +503,45 @@ 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(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 v5 3/3] samples: rust: add Rust I2C sample driver

[Igor Korotin]

Add a new `rust_driver_i2c` sample, showing how to create a new
i2c client using `i2c::Registration` and bind a driver to it
via legacy I2C-ID table.

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 | 128 ++++++++++++++++++++++++++++++++
 4 files changed, 141 insertions(+)
 create mode 100644 samples/rust/rust_driver_i2c.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index c44c7ac317b1..2654a7ea0c80 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11523,6 +11523,7 @@ 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 7f7371a004ee..28dae070b365 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -62,6 +62,17 @@ config SAMPLE_RUST_DMA
 
 	  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 bd2faad63b4f..141d8f078248 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -5,6 +5,7 @@ obj-$(CONFIG_SAMPLE_RUST_MINIMAL)		+= rust_minimal.o
 obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE)		+= rust_misc_device.o
 obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o
 obj-$(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_FAUX)		+= rust_driver_faux.o
diff --git a/samples/rust/rust_driver_i2c.rs b/samples/rust/rust_driver_i2c.rs
new file mode 100644
index 000000000000..c73b89abbac6
--- /dev/null
+++ b/samples/rust/rust_driver_i2c.rs
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust I2C driver sample.
+//!
+//! This module shows how to:
+//!
+//! 1. Manually create an `i2c_client` at address `SAMPLE_I2C_CLIENT_ADDR`
+//!    on the adapter with index `SAMPLE_I2C_ADAPTER_INDEX`.
+//!
+//! 2. Register a matching Rust-based I2C driver for that client.
+//!
+//! # Requirements
+//!
+//! - The target system must expose an I2C adapter at index
+//!   `SAMPLE_I2C_ADAPTER_INDEX`.
+//!
+//! - To emulate an adapter for testing, you can load the
+//!   `i2c-stub` kernel module with an option `chip_addr`
+//!   For example for this sample driver to emulate an I2C device with
+//!   an address 0x30 you can use:
+//!      `modprobe i2c-stub chip_addr=0x30`
+//!
+
+use kernel::{
+    acpi, c_str,
+    device::{Core, Normal},
+    i2c, of,
+    prelude::*,
+    types::ARef,
+};
+
+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);
+
+struct SampleDriver {
+    idev: ARef<i2c::I2cClient>,
+}
+
+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>) -> Result<Pin<KBox<Self>>> {
+        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);
+        }
+
+        let drvdata = KBox::new(Self { idev: idev.into() }, GFP_KERNEL)?;
+
+        Ok(drvdata.into())
+    }
+
+    fn shutdown(idev: &i2c::I2cClient<Core>) {
+        dev_info!(idev.as_ref(), "Shutdown Rust I2C driver sample.\n");
+    }
+}
+
+impl Drop for SampleDriver {
+    fn drop(&mut self) {
+        dev_info!(self.idev.as_ref(), "Remove Rust I2C driver sample.\n");
+    }
+}
+
+// NOTE: The code below is expanded macro module_i2c_driver. It is not used here
+//       because we need to manually create an I2C client in `init()`. The macro
+//       hides `init()`, so to demo client creation on adapter SAMPLE_I2C_ADAPTER_INDEX
+//       we expand it by hand.
+type Ops<T> = kernel::i2c::Adapter<T>;
+
+#[pin_data]
+struct DriverModule {
+    #[pin]
+    _driver: kernel::driver::Registration<Ops<SampleDriver>>,
+    _reg: i2c::Registration,
+}
+
+impl kernel::InPlaceModule for DriverModule {
+    fn init(
+        module: &'static kernel::ThisModule,
+    ) -> impl ::pin_init::PinInit<Self, kernel::error::Error> {
+        kernel::try_pin_init!(Self {
+            _reg <- {
+                let adapter = i2c::I2cAdapter::<Normal>::get(SAMPLE_I2C_ADAPTER_INDEX)?;
+
+                i2c::Registration::new(adapter.as_ref(), &BOARD_INFO)
+            },
+            _driver <- kernel::driver::Registration::new(<Self as kernel::ModuleMetadata>::NAME,module,),
+        })
+    }
+}
+
+kernel::prelude::module! {
+    type: DriverModule,
+    name: "rust_driver_i2c",
+    authors: ["Igor Korotin"],
+    description: "Rust I2C driver",
+    license: "GPL v2",
+}
-- 
2.43.0

Re: [PATCH v5 1/3] rust: i2c: add basic I2C device and driver abstractions

[Daniel Almeida]

Hi Igor,

> On 11 Sep 2025, at 12:49, Igor Korotin <igor.korotin.linux@gmail.com> 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>

I’m a bit swamped for the next 2-3 days, but I will review this soon.

Feel free to ping me otherwise.

— Daniel

Re: [PATCH v5 1/3] rust: i2c: add basic I2C device and driver abstractions

[Danilo Krummrich]

On Thu Sep 11, 2025 at 5:49 PM CEST, Igor Korotin wrote:
> +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>,
> +    ) -> Result<Pin<KBox<Self>>>;
> +
> +    /// I2C driver shutdown
> +    ///
> +    /// Called when

Seems like you did forget to actually finish the comment.

> +    fn shutdown(dev: &I2cClient<device::Core>) {

You should also provide a Pin<&Self> argument.

> +        let _ = dev;
> +    }

Can you please also add an unbind() method analogous to PCI, platform, etc.? It
avoids that people have to use try_access() for accessing device resources on
remove().

Re: [PATCH v5 2/3] rust: i2c: add manual I2C device creation abstractions

[Danilo Krummrich]

On Thu Sep 11, 2025 at 5:50 PM CEST, Igor Korotin wrote:
> +impl I2cAdapter {
> +    /// Gets pointer to an `i2c_adapter` by index.
> +    pub fn get(index: i32) -> Result<ARef<Self>> {

Where do we get this index usually from? OF, ACPI, etc. I assume? I feel like it
could make sense to wrap it into a new type. Even though it is not safety
relevant it eliminates a source for mistakes.

> +        // 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() })
> +    }
> +}
> +
> +impl<Ctx: device::DeviceContext> Drop for I2cAdapter<Ctx> {
> +    fn drop(&mut self) {
> +        // SAFETY: This `I2cAdapter` was obtained from `i2c_get_adapter`,
> +        // and calling `i2c_put_adapter` exactly once will correctly release
> +        // the reference count in the I2C core. It is safe to call from any context
> +        unsafe { bindings::i2c_put_adapter(self.as_raw()) }
> +    }
> +}

The Drop implementation is not needed, you only ever give out an
ARef<I2cAdapter>, but never a "raw" I2cAdapter, which is the correct thing to
do.

> +
> +// 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.as_raw()).nr) };

Please make accessing the nr field a separate inline function, or at least put
it in a separate unsafe block.

> +    }
> +
> +    unsafe fn dec_ref(obj: NonNull<Self>) {
> +        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
> +        unsafe { bindings::i2c_put_adapter(&raw mut (*obj.as_ref().as_raw())) }

Same here, separate unsafe blocks please.

> +    }
> +}
> +
> +impl<Ctx: device::DeviceContext> AsRef<I2cAdapter<Ctx>> for I2cAdapter<Ctx> {
> +    fn as_ref(&self) -> &I2cAdapter<Ctx> {
> +        &self
> +    }
> +}

This AsRef implementation doesn't seem to do anything?

Re: [PATCH v5 3/3] samples: rust: add Rust I2C sample driver

[Danilo Krummrich]

On Thu Sep 11, 2025 at 5:50 PM CEST, Igor Korotin wrote:
> +// NOTE: The code below is expanded macro module_i2c_driver. It is not used here
> +//       because we need to manually create an I2C client in `init()`. The macro
> +//       hides `init()`, so to demo client creation on adapter SAMPLE_I2C_ADAPTER_INDEX
> +//       we expand it by hand.
> +type Ops<T> = kernel::i2c::Adapter<T>;

Not a huge fan of this type alias, but up to you. :)

> +#[pin_data]
> +struct DriverModule {
> +    #[pin]
> +    _driver: kernel::driver::Registration<Ops<SampleDriver>>,
> +    _reg: i2c::Registration,
> +}
> +
> +impl kernel::InPlaceModule for DriverModule {
> +    fn init(
> +        module: &'static kernel::ThisModule,
> +    ) -> impl ::pin_init::PinInit<Self, kernel::error::Error> {
> +        kernel::try_pin_init!(Self {
> +            _reg <- {
> +                let adapter = i2c::I2cAdapter::<Normal>::get(SAMPLE_I2C_ADAPTER_INDEX)?;

Just i2c::I2cAdapter::get() is fine.

> +
> +                i2c::Registration::new(adapter.as_ref(), &BOARD_INFO)

Does i2c_new_client_device() grab a reference count of the adapter? If not, you
have to store an ARef<I2cAdapter> within your i2c::Registration as well.

> +            },
> +            _driver <- kernel::driver::Registration::new(<Self as kernel::ModuleMetadata>::NAME,module,),
> +        })
> +    }
> +}

Re: [PATCH v5 2/3] rust: i2c: add manual I2C device creation abstractions

[Igor Korotin]

Hello Danilo

On 9/11/2025 9:34 PM, Danilo Krummrich wrote:
> On Thu Sep 11, 2025 at 5:50 PM CEST, Igor Korotin wrote:
>> +impl I2cAdapter {
>> +    /// Gets pointer to an `i2c_adapter` by index.
>> +    pub fn get(index: i32) -> Result<ARef<Self>> {
> 
> Where do we get this index usually from? OF, ACPI, etc. I assume? I feel like it
> could make sense to wrap it into a new type. Even though it is not safety
> relevant it eliminates a source for mistakes.

It usually comes as predefined magic number in a platform driver info.
I'll define a specific type for this number for clearance.

>> +    }
>> +}
>> +
>> +impl<Ctx: device::DeviceContext> AsRef<I2cAdapter<Ctx>> for I2cAdapter<Ctx> {
>> +    fn as_ref(&self) -> &I2cAdapter<Ctx> {
>> +        &self
>> +    }
>> +}
> 
> This AsRef implementation doesn't seem to do anything?

I misunderstood the concept of the ARef<T> a little bit and used this 
as_ref() instead of just getting a reference by &adapter. I'll remove 
this in the next drop

Thanks for the review. All other comments are noted. I'll address them 
in the next drop as well

Cheers
Igor

Re: [PATCH v5 3/3] samples: rust: add Rust I2C sample driver

[Igor Korotin]

Hello Danilo

On 9/11/2025 9:46 PM, Danilo Krummrich wrote:
> On Thu Sep 11, 2025 at 5:50 PM CEST, Igor Korotin wrote:
>> +// NOTE: The code below is expanded macro module_i2c_driver. It is not used here
>> +//       because we need to manually create an I2C client in `init()`. The macro
>> +//       hides `init()`, so to demo client creation on adapter SAMPLE_I2C_ADAPTER_INDEX
>> +//       we expand it by hand.
>> +type Ops<T> = kernel::i2c::Adapter<T>;
> 
> Not a huge fan of this type alias, but up to you. :)

I literally just unwrapped module_driver! macro to get to the init 
function.
This type was part of that macro. I do not see it necessary, so I'll 
remove it
in the next drop.
  >> +
>> +                i2c::Registration::new(adapter.as_ref(), &BOARD_INFO)
> 
> Does i2c_new_client_device() grab a reference count of the adapter? If not, you
> have to store an ARef<I2cAdapter> within your i2c::Registration as well.

Well, as far as I traced the C code, `adapter->dev` is a 
`client->dev->parent`. Inside of the i2c_new_client_device the new 
created client device is being registered and as part of this 
registration device's parent reference count is being incremented.

A big thanks for the review and comments.

Regards
Igor