rust: i2c: add basic I2C device and driver abstractions (57c5bd9a) · Commits · git / linux-net

MAINTAINERS

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		@@ -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

rust/bindings/bindings_helper.h

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		@@ -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>

rust/kernel/i2c.rs

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		// 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();
		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
		/// [`I2cClient`] 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 the [`I2cClient`] 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 {}

rust/kernel/lib.rs

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		@@ -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;