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Sun, 05 Oct 2025 03:23:31 -0700 (PDT) From: Igor Korotin To: Miguel Ojeda , Alex Gaynor , Wolfram Sang Cc: Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Greg Kroah-Hartman , Viresh Kumar , Asahi Lina , Wedson Almeida Filho , Alex Hung , Tamir Duberstein , Xiangfei Ding , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-i2c@vger.kernel.org Subject: [PATCH v6 1/3] rust: i2c: add basic I2C device and driver abstractions Date: Sun, 5 Oct 2025 11:23:28 +0100 Message-ID: <20251005102328.41899-1-igor.korotin.linux@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251005102226.41876-1-igor.korotin.linux@gmail.com> References: <20251005102226.41876-1-igor.korotin.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Implement the core abstractions needed for I2C drivers, including: * `i2c::Driver` =E2=80=94 the trait drivers must implement, including `prob= e` * `i2c::I2cClient` =E2=80=94 a safe wrapper around `struct i2c_client` * `i2c::Adapter` =E2=80=94 implements `driver::RegistrationOps` to hook int= o the generic `driver::Registration` machinery * `i2c::DeviceId` =E2=80=94 a `RawDeviceIdIndex` implementation for I2C dev= ice IDs Signed-off-by: Igor Korotin --- MAINTAINERS | 8 + rust/bindings/bindings_helper.h | 1 + rust/kernel/i2c.rs | 423 ++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 2 + 4 files changed, 434 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 =20 +I2C SUBSYSTEM [RUST] +M: Igor Korotin +R: Danilo Krummrich +R: Daniel Almeida +L: rust-for-linux@vger.kernel.org +S: Maintained +F: rust/kernel/i2c.rs + I2C SUBSYSTEM HOST DRIVERS M: Andi Shyti L: linux-i2c@vger.kernel.org diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helpe= r.h index 84d60635e8a9..81796d5e16e8 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -53,6 +53,7 @@ #include #include #include +#include #include #include #include diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs new file mode 100644 index 000000000000..c5a8a5791523 --- /dev/null +++ b/rust/kernel/i2c.rs @@ -0,0 +1,423 @@ +// 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 =3D 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() <=3D Self::I2C_NAME_SIZE, + "ID exceeds 20 bytes" + ); + let src =3D id.as_bytes_with_nul(); + // Replace with `bindings::acpi_device_id::default()` once stabili= zed for `const`. + // SAFETY: FFI type is valid to be zero-initialized. + let mut i2c: bindings::i2c_device_id =3D unsafe { core::mem::zeroe= d() }; + let mut i =3D 0; + while i < src.len() { + i2c.name[i] =3D src[i]; + i +=3D 1; + } + + Self(i2c) + } +} + +// SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `i2c_device_i= d` and does not add +// additional invariants, so it's safe to transmute to `RawType`. +unsafe impl RawDeviceId for DeviceId { + type RawType =3D 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 =3D core::mem::offset_of!(bindings::i2= c_device_id, driver_data); + + fn index(&self) -> usize { + self.0.driver_data + } +} + +/// IdTable type for I2C +pub type IdTable =3D &'static dyn kernel::device_id::IdTable; + +/// 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, $tabl= e_data: expr) =3D> { + const $table_name: $crate::device_id::IdArray< + $crate::i2c::DeviceId, + $id_info_type, + { $table_data.len() }, + > =3D $crate::device_id::IdArray::new($table_data); + + $crate::module_device_table!("i2c", $module_table_name, $table_nam= e); + }; +} + +/// An adapter for the registration of I2C drivers. +pub struct Adapter(T); + +// SAFETY: A call to `unregister` for a given instance of `RegType` is gua= ranteed to be valid if +// a preceding call to `register` has been successful. +unsafe impl driver::RegistrationOps for Adapter { + type RegType =3D bindings::i2c_driver; + + unsafe fn register( + idrv: &Opaque, + name: &'static CStr, + module: &'static ThisModule, + ) -> Result { + build_assert!( + T::ACPI_ID_TABLE.is_some() || T::OF_ID_TABLE.is_some() || T::I= 2C_ID_TABLE.is_some(), + "At least one of ACPI/OF/Legacy tables must be present when re= gistering an i2c driver" + ); + + let i2c_table =3D match T::I2C_ID_TABLE { + Some(table) =3D> table.as_ptr(), + None =3D> core::ptr::null(), + }; + + let of_table =3D match T::OF_ID_TABLE { + Some(table) =3D> table.as_ptr(), + None =3D> core::ptr::null(), + }; + + let acpi_table =3D match T::ACPI_ID_TABLE { + Some(table) =3D> table.as_ptr(), + None =3D> core::ptr::null(), + }; + + // SAFETY: It's safe to set the fields of `struct i2c_client` on i= nitialization. + unsafe { + (*idrv.get()).driver.name =3D name.as_char_ptr(); + (*idrv.get()).probe =3D Some(Self::probe_callback); + (*idrv.get()).remove =3D Some(Self::remove_callback); + (*idrv.get()).shutdown =3D Some(Self::shutdown_callback); + (*idrv.get()).id_table =3D i2c_table; + (*idrv.get()).driver.of_match_table =3D of_table; + (*idrv.get()).driver.acpi_match_table =3D acpi_table; + } + + // SAFETY: `idrv` is guaranteed to be a valid `RegType`. + to_result(unsafe { bindings::i2c_register_driver(module.0, idrv.ge= t()) }) + } + + unsafe fn unregister(idrv: &Opaque) { + // SAFETY: `idrv` is guaranteed to be a valid `RegType`. + unsafe { bindings::i2c_del_driver(idrv.get()) } + } +} + +impl Adapter { + extern "C" fn probe_callback(idev: *mut bindings::i2c_client) -> kerne= l::ffi::c_int { + // SAFETY: The I2C bus only ever calls the probe callback with a v= alid pointer to a + // `struct i2c_client`. + // + // INVARIANT: `idev` is valid for the duration of `probe_callback(= )`. + let idev =3D unsafe { &*idev.cast::>() }; + + let info =3D + Self::i2c_id_info(idev).or_else(|| ::= id_info(idev.as_ref())); + + from_result(|| { + let data =3D 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 =3D unsafe { &*idev.cast::>() }; + + // SAFETY: `remove_callback` is only ever called after a successfu= l call to + // `probe_callback`, hence it's guaranteed that `I2cClient::set_dr= vdata()` has been called + // and stored a `Pin>`. + drop(unsafe { idev.as_ref().drvdata_obtain::>>() }); + } + + extern "C" fn shutdown_callback(idev: *mut bindings::i2c_client) { + // SAFETY: `shutdown_callback` is only ever called for a valid `id= ev` + let idev =3D unsafe { &*idev.cast::>() }; + + // SAFETY: `shutdown_callback` is only ever called after a success= ful call to + // `probe_callback`, hence it's guaranteed that `Device::set_drvda= ta()` has been called + // and stored a `Pin>`. + let data =3D unsafe { idev.as_ref().drvdata_obtain::>>= () }; + + T::shutdown(idev, data.as_ref()); + } + + /// The [`i2c::IdTable`] of the corresponding driver. + fn i2c_id_table() -> Option::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 i= n the [`i2c::IdTable`]. + fn i2c_id_info(dev: &I2cClient) -> Option<&'static ::IdInfo> { + let table =3D 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 =3D 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 `struc= t i2c_device_id` and + // does not add additional invariants, so it's safe to transmute. + let id =3D unsafe { &*raw_id.cast::() }; + + Some(table.info(::index(id))) + } +} + +impl driver::Adapter for Adapter { + type IdInfo =3D T::IdInfo; + + fn of_id_table() -> Option> { + T::OF_ID_TABLE + } + + fn acpi_id_table() -> Option> { + 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)*) =3D> { + $crate::module_driver!(, $crate::i2c::Adapter, { $($f)* }); + }; +} + +/// The i2c driver trait. +/// +/// Drivers must implement this trait in order to get a i2c driver registe= red. +/// +/// # Example +/// +///``` +/// # use kernel::{acpi, bindings, c_str, device::Core, i2c, of}; +/// +/// struct MyDriver; +/// +/// kernel::acpi_device_table!( +/// ACPI_TABLE, +/// MODULE_ACPI_TABLE, +/// ::IdInfo, +/// [ +/// (acpi::DeviceId::new(c_str!("LNUXBEEF")), ()) +/// ] +/// ); +/// +/// kernel::i2c_device_table!( +/// I2C_TABLE, +/// MODULE_I2C_TABLE, +/// ::IdInfo, +/// [ +/// (i2c::DeviceId::new(c_str!("rust_driver_i2c")), ()) +/// ] +/// ); +/// +/// kernel::of_device_table!( +/// OF_TABLE, +/// MODULE_OF_TABLE, +/// ::IdInfo, +/// [ +/// (of::DeviceId::new(c_str!("test,device")), ()) +/// ] +/// ); +/// +/// impl i2c::Driver for MyDriver { +/// type IdInfo =3D (); +/// const I2C_ID_TABLE: Option> =3D Some(&I= 2C_TABLE); +/// const OF_ID_TABLE: Option> =3D Some(&OF_= TABLE); +/// const ACPI_ID_TABLE: Option> =3D Some(= &ACPI_TABLE); +/// +/// fn probe( +/// _idev: &i2c::I2cClient, +/// _id_info: Option<&Self::IdInfo>, +/// ) -> Result>> { +/// Err(ENODEV) +/// } +/// +/// fn shutdown(_idev: &i2c::I2cClient, 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 =3D (); + // ``` + type IdInfo: 'static; + + /// The table of device ids supported by the driver. + const I2C_ID_TABLE: Option> =3D None; + + /// The table of OF device ids supported by the driver. + const OF_ID_TABLE: Option> =3D None; + + /// The table of ACPI device ids supported by the driver. + const ACPI_ID_TABLE: Option> =3D 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, + id_info: Option<&Self::IdInfo>, + ) -> Result>>; + + /// I2C driver shutdown. + /// + /// Called by the kernel during system reboot or power-off to allow th= e [`Driver`] to bring the + /// [`Device`] into a safe state. Implementing this callback is option= al. + /// + /// 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 driv= er instance remains valid + /// after it returns. Any deallocation or teardown of driver-owned res= ources should instead be + /// handled in `Self::drop`. + fn shutdown(dev: &I2cClient, this: Pin<&Self>) { + let _ =3D (dev, this); + } + + /// I2C driver unbind. + /// + /// Called when a [`Device`] is unbound from its bound [`Driver`]. Imp= lementing this callback + /// is optional. + /// + /// This callback serves as a place for drivers to perform teardown op= erations that require a + /// `&Device` or `&Device` reference. For instance, drive= rs may try to perform I/O + /// operations to gracefully tear down the device. + /// + /// Otherwise, release operations for driver resources should be perfo= rmed in `Self::drop`. + fn unbind(dev: &I2cClient, this: Pin<&Self>) { + let _ =3D (dev, this); + } +} + +/// The i2c client representation. +/// +/// This structure represents the Rust abstraction for a C `struct i2c_cli= ent`. 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` create= d by the C portion of +/// the kernel. +#[repr(transparent)] +pub struct I2cClient( + Opaque, + PhantomData, +); + +impl I2cClient { + fn as_raw(&self) -> *mut bindings::i2c_client { + self.0.get() + } +} + +// SAFETY: `I2cClient` is a transparent wrapper of a type that doesn't dep= end 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) { + // SAFETY: The safety requirements guarantee that the refcount is = non-zero. + unsafe { bindings::put_device(&raw mut (*obj.as_ref().as_raw()).de= v) } + } +} + +impl AsRef> for I2cClient<= Ctx> { + fn as_ref(&self) -> &device::Device { + let raw =3D self.as_raw(); + // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a p= ointer to a valid + // `struct i2c_client`. + let dev =3D unsafe { &raw mut (*raw).dev }; + + // SAFETY: `dev` points to a valid `struct device`. + unsafe { device::Device::from_raw(dev) } + } +} + +impl TryFrom<&device::Device> for &I2cCli= ent { + type Error =3D kernel::error::Error; + + fn try_from(dev: &device::Device) -> Result { + // 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 =3D unsafe { container_of!(dev.as_raw(), bindings::i2c_cl= ient, 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 f= rom any thread. +unsafe impl Send for I2cClient {} + +// SAFETY: `I2cClient` can be shared among threads because all methods of = `I2cClient` +// (i.e. `I2cClient) 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; 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Sun, 05 Oct 2025 03:23:43 -0700 (PDT) From: Igor Korotin To: Miguel Ojeda , Alex Gaynor , Wolfram Sang Cc: Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Greg Kroah-Hartman , Viresh Kumar , Asahi Lina , Wedson Almeida Filho , Alex Hung , Tamir Duberstein , Xiangfei Ding , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-i2c@vger.kernel.org Subject: [PATCH v6 2/3] rust: i2c: add manual I2C device creation abstractions Date: Sun, 5 Oct 2025 11:23:40 +0100 Message-ID: <20251005102340.41917-1-igor.korotin.linux@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251005102226.41876-1-igor.korotin.linux@gmail.com> References: <20251005102226.41876-1-igor.korotin.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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` =E2=80=94 a NonNull pointer created by the function `i2c_new_client_device` * `i2c::I2cAdapter` =E2=80=94 a ref counted wrapper around `struct i2c_ada= pter` * `i2c::I2cBoardInfo` =E2=80=94 a safe wrapper around `struct i2c_board_in= fo` Signed-off-by: Igor Korotin --- rust/kernel/i2c.rs | 144 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 143 insertions(+), 1 deletion(-) diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs index c5a8a5791523..73858aecc131 100644 --- a/rust/kernel/i2c.rs +++ b/rust/kernel/i2c.rs @@ -13,7 +13,12 @@ types::{AlwaysRefCounted, Opaque}, }; =20 -use core::{marker::PhantomData, ptr::NonNull}; +use core::{ + marker::PhantomData, + ptr::{from_ref, NonNull}, +}; + +use kernel::types::ARef; =20 /// An I2C device id table. #[repr(transparent)] @@ -343,6 +348,101 @@ fn unbind(dev: &I2cClient, this: Pin<&S= elf>) { } } =20 +/// The i2c adapter representation. +/// +/// This structure represents the Rust abstraction for a C `struct i2c_ada= pter`. The +/// implementation abstracts the usage of an existing C `struct i2c_adapte= r` that +/// gets passed from the C side +/// +/// # Invariants +/// +/// A [`I2cAdapter`] instance represents a valid `struct i2c_adapter` crea= ted by the C portion of +/// the kernel. +#[repr(transparent)] +pub struct I2cAdapter( + Opaque, + PhantomData, +); + +impl I2cAdapter { + fn as_raw(&self) -> *mut bindings::i2c_adapter { + self.0.get() + } +} + +impl I2cAdapter { + /// Returns the I2C Adapter index. + #[inline] + pub fn get_nr(&self) -> i32 { + // SAFETY: `self.as_raw` is a valid pointer to a `struct i2c_adapt= er`. + unsafe { (*self.as_raw()).nr } + } + /// Gets pointer to an `i2c_adapter` by index. + pub fn get(index: i32) -> Result> { + // 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 =3D NonNull::new(unsafe { bindings::i2c_get_adapter(in= dex) }).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::>= ()).into() }) + } +} + +// SAFETY: `I2cAdapter` is a transparent wrapper of a type that doesn't de= pend 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.get_nr()) }; + } + + unsafe fn dec_ref(obj: NonNull) { + // 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_boa= rd_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 =3D 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() <=3D Self::I2C_TYPE_SIZE, + "Type exceeds 20 bytes" + ); + let src =3D type_.as_bytes_with_nul(); + // Replace with `bindings::acpi_device_id::default()` once stabili= zed for `const`. + // SAFETY: FFI type is valid to be zero-initialized. + let mut i2c_board_info: bindings::i2c_board_info =3D unsafe { core= ::mem::zeroed() }; + let mut i: usize =3D 0; + while i < src.len() { + i2c_board_info.type_[i] =3D src[i]; + i +=3D 1; + } + + i2c_board_info.addr =3D 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_cli= ent`. The @@ -421,3 +521,45 @@ unsafe impl Send for I2cClient {} // SAFETY: `I2cClient` can be shared among threads because all methods of = `I2cClient` // (i.e. `I2cClient) 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); + +impl Registration { + /// The C `i2c_new_client_device` function wrapper for manual I2C clie= nt creation. + pub fn new(i2c_adapter: &I2cAdapter, i2c_board_info: &I2cBoardInfo) ->= Result { + // SAFETY: the kernel guarantees that `i2c_new_client_device()` re= turns either a valid + // pointer or NULL. `from_err_ptr` separates errors. Following `No= nNull::new` checks for NULL. + let raw_dev =3D from_err_ptr(unsafe { + bindings::i2c_new_client_device(i2c_adapter.as_raw(), i2c_boar= d_info.as_raw()) + })?; + + let dev_ptr =3D 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 throu= gh &self +// and no mutable access is exposed) +unsafe impl Sync for Registration {} --=20 2.43.0 From nobody Tue Oct 7 22:35:58 2025 Received: from mail-wr1-f51.google.com (mail-wr1-f51.google.com [209.85.221.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A53DC26C399 for ; 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Sun, 05 Oct 2025 03:23:51 -0700 (PDT) Received: from Vasilio.Home ([2.127.51.206]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4255d8e9703sm16055425f8f.30.2025.10.05.03.23.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 05 Oct 2025 03:23:51 -0700 (PDT) From: Igor Korotin To: Miguel Ojeda , Alex Gaynor , Wolfram Sang Cc: Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Greg Kroah-Hartman , Viresh Kumar , Asahi Lina , Wedson Almeida Filho , Alex Hung , Tamir Duberstein , Xiangfei Ding , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-i2c@vger.kernel.org Subject: [PATCH v6 3/3] samples: rust: add Rust I2C sample driver Date: Sun, 5 Oct 2025 11:23:48 +0100 Message-ID: <20251005102348.41935-1-igor.korotin.linux@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251005102226.41876-1-igor.korotin.linux@gmail.com> References: <20251005102226.41876-1-igor.korotin.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 --- MAINTAINERS | 1 + samples/rust/Kconfig | 11 +++ samples/rust/Makefile | 1 + samples/rust/rust_driver_i2c.rs | 126 ++++++++++++++++++++++++++++++++ 4 files changed, 139 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 L: rust-for-linux@vger.kernel.org S: Maintained F: rust/kernel/i2c.rs +F: samples/rust/rust_driver_i2c.rs =20 I2C SUBSYSTEM HOST DRIVERS M: Andi Shyti 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 =20 If unsure, say N. =20 +config SAMPLE_RUST_DRIVER_I2C + tristate "I2C Driver" + depends on I2C=3Dy + 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-$(CONFIG_SAMPLE_RUST_MINIMAL) +=3D rust_minimal.o obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE) +=3D rust_misc_device.o obj-$(CONFIG_SAMPLE_RUST_PRINT) +=3D rust_print.o obj-$(CONFIG_SAMPLE_RUST_DMA) +=3D rust_dma.o +obj-$(CONFIG_SAMPLE_RUST_DRIVER_I2C) +=3D rust_driver_i2c.o obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI) +=3D rust_driver_pci.o obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM) +=3D rust_driver_platform.o obj-$(CONFIG_SAMPLE_RUST_DRIVER_FAUX) +=3D 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..b2d1d234b077 --- /dev/null +++ b/samples/rust/rust_driver_i2c.rs @@ -0,0 +1,126 @@ +// 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=3D0x30` +//! + +use kernel::{ + acpi, c_str, + device::Core, + i2c, of, + prelude::*, + types::ARef, +}; + +const SAMPLE_I2C_CLIENT_ADDR: u16 =3D 0x30; +const SAMPLE_I2C_ADAPTER_INDEX: i32 =3D 0; +const BOARD_INFO: i2c::I2cBoardInfo =3D + i2c::I2cBoardInfo::new(c_str!("rust_driver_i2c"), SAMPLE_I2C_CLIENT_AD= DR); + +struct SampleDriver { + idev: ARef, +} + +kernel::acpi_device_table! { + ACPI_TABLE, + MODULE_ACPI_TABLE, + ::IdInfo, + [(acpi::DeviceId::new(c_str!("LNUXBEEF")), 0)] +} + +kernel::i2c_device_table! { + I2C_TABLE, + MODULE_I2C_TABLE, + ::IdInfo, + [(i2c::DeviceId::new(c_str!("rust_driver_i2c")), 0)] +} + +kernel::of_device_table! { + OF_TABLE, + MODULE_OF_TABLE, + ::IdInfo, + [(of::DeviceId::new(c_str!("test,rust_driver_i2c")), 0)] +} + +impl i2c::Driver for SampleDriver { + type IdInfo =3D u32; + + const ACPI_ID_TABLE: Option> =3D Some(&ACP= I_TABLE); + const I2C_ID_TABLE: Option> =3D Some(&I2C_T= ABLE); + const OF_ID_TABLE: Option> =3D Some(&OF_TABL= E); + + fn probe(idev: &i2c::I2cClient, info: Option<&Self::IdInfo>) -> = Result>> { + let dev =3D idev.as_ref(); + + dev_info!(dev, "Probe Rust I2C driver sample.\n"); + + if let Some(info) =3D info { + dev_info!(dev, "Probed with info: '{}'.\n", info); + } + + let drvdata =3D KBox::new(Self { idev: idev.into() }, GFP_KERNEL)?; + + Ok(drvdata.into()) + } + + fn shutdown(idev: &i2c::I2cClient, _this: Pin<&Self>) { + 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 use= d 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. +#[pin_data] +struct DriverModule { + #[pin] + _driver: kernel::driver::Registration>, + _reg: i2c::Registration, +} + +impl kernel::InPlaceModule for DriverModule { + fn init( + module: &'static kernel::ThisModule, + ) -> impl ::pin_init::PinInit { + kernel::try_pin_init!(Self { + _reg <- { + let adapter =3D i2c::I2cAdapter::get(SAMPLE_I2C_ADAPTER_IN= DEX)?; + + i2c::Registration::new(&adapter, &BOARD_INFO) + }, + _driver <- kernel::driver::Registration::new(::NAME,module,), + }) + } +} + +kernel::prelude::module! { + type: DriverModule, + name: "rust_driver_i2c", + authors: ["Igor Korotin"], + description: "Rust I2C driver", + license: "GPL v2", +} --=20 2.43.0