From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A32B184 for ; Sat, 2 Aug 2025 00:00:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754092820; cv=none; b=ZRp7R5n+9F5+b6AssKFSPUtBFLmc0/SQLJB+ofctlwFhK0Dsh2UpfHDD3EeS4kVX1JigzJKYssNQo1laO579Wf3h98/xw2TO2M7LgDzQ9sFy4R6j2iGgjsRJtpD77GDcgAi9k6xObaoXvW/FYOlfI5QNBXcQAiMaS/BEalneYTs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754092820; c=relaxed/simple; bh=DD7H503m0oiQfyOQ/IZhwQFebV7539426/6uc2Evyi8=; h=Mime-Version:Content-Type:Date:Message-Id:Cc:To:From:Subject: References:In-Reply-To; b=EEzN6vodZSqC9Va1oWfEoZwgZZVddbGqMLM7f7qaOxpdlezlO0bZn6zLAAIy4VUb9hkT/8NCmrz/3v0+8PKmVCGsbZCfTv5OL5QmMn5XdrLrqJKNZPjrnLQhcDHizffwiFYZsM0mS3gKx+lKTbnyfIKkU1AOe+REKIdm3pc9Ejo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=D828F6K2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="D828F6K2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6592C4CEE7; Sat, 2 Aug 2025 00:00:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754092820; bh=DD7H503m0oiQfyOQ/IZhwQFebV7539426/6uc2Evyi8=; h=Date:Cc:To:From:Subject:References:In-Reply-To:From; b=D828F6K2yLaBtCC/oz4jctmBOKmZhqXEkd7s1EzZtYd8TDfWRp9M4svqJGnXHmo5p Q8TfSAkUF6EuUmXcGDR9Tn4nrhZLZ1seOIC54e6WggwD49/xFJoCkD3QXeUg6BPOGb sI9xozYpjDPeSe42yZMZMsrXr/Dp7o9so1Ol/CizT2eaHHeO5Mc5cW1yNKBVB67hUN e3AsQNc9lhdpu/q5DXbUNFLWTGV87RVznSP7jvzBp76SouWe+TNvZ7x8mQBd+9ttEY 2A3OzS6E4StG7i5NJPj+0z9mOGoemEvlhk/zkkn9hBDYYNGoL+tnva6AjQbcWrInkq g9hsEEBxJgRTQ== Precedence: bulk X-Mailing-List: rust-for-linux@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 Date: Sat, 02 Aug 2025 02:00:15 +0200 Message-Id: Cc: "Miguel Ojeda" , "Alex Gaynor" , "Boqun Feng" , "Gary Guo" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Alice Ryhl" , "Trevor Gross" , , "Wolfram Sang" To: "Igor Korotin" From: "Danilo Krummrich" Subject: Re: [PATCH v3 1/3] rust: i2c: add basic I2C device and driver abstractions References: <20250801153742.13472-1-igor.korotin.linux@gmail.com> <20250801154042.14327-1-igor.korotin.linux@gmail.com> In-Reply-To: <20250801154042.14327-1-igor.korotin.linux@gmail.com> (Cc: Wolfram) On Fri Aug 1, 2025 at 5:40 PM CEST, Igor Korotin wrote: > Implement the core abstractions needed for I2C drivers, including: > > * `i2c::Driver` =E2=80=94 the trait drivers must implement, including `pr= obe` > > * `i2c::Device` =E2=80=94 a safe wrapper around `struct i2c_client` > > * `i2c::Adapter` =E2=80=94 implements `driver::RegistrationOps` to hook i= nto the > generic `driver::Registration` machinery > > * `i2c::DeviceId` =E2=80=94 a `RawDeviceIdIndex` implementation for I2C d= evice IDs > > Signed-off-by: Igor Korotin > --- > MAINTAINERS | 7 + > rust/bindings/bindings_helper.h | 1 + > rust/kernel/i2c.rs | 391 ++++++++++++++++++++++++++++++++ > rust/kernel/lib.rs | 2 + > 4 files changed, 401 insertions(+) > create mode 100644 rust/kernel/i2c.rs > > diff --git a/MAINTAINERS b/MAINTAINERS > index 4f03e230f3c5..767beaa0f7c2 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -11514,6 +11514,13 @@ F: include/linux/i2c.h > F: include/uapi/linux/i2c-*.h > F: include/uapi/linux/i2c.h > =20 > +I2C SUBSYSTEM [RUST] Has this been agreed with Wolfram off-list? (I'm asking since I haven't see= n a reply from him in v2.) In case you just did not receive an answer yet, it's fine to proceed with a proposal as you do here. However, please make sure to keep Wolfram in the l= oop. :) In either case, which tree should patches flow through? > +M: Igor Korotin > +R: Danilo Krummrich If you'd like me to keep an eye on this as well, this is fine with me. > +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_hel= per.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..fafcae92cfdb > --- /dev/null > +++ b/rust/kernel/i2c.rs > @@ -0,0 +1,391 @@ > +// 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::Opaque, > +}; > + > +use core::{ > + marker::PhantomData, > + ptr::{addr_of_mut, 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 stabi= lized for `const`. > + // SAFETY: FFI type is valid to be zero-initialized. > + let mut i2c: bindings::i2c_device_id =3D unsafe { core::mem::zer= oed() }; > + 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= _id` 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::= i2c_device_id, driver_data); > + > + fn index(&self) -> usize { > + self.0.driver_data as _ This cast shouldn't be needed. > + } > +} > + > +/// 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, $ta= ble_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_n= ame); > + }; > +} > + > +/// An adapter for the registration of I2C drivers. > +pub struct Adapter(T); > + > +// SAFETY: A call to `unregister` for a given instance of `RegType` is g= uaranteed 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( > + pdrv: &Opaque, Rather idrv or similar I think; same for various cases below. > + name: &'static CStr, > + module: &'static ThisModule, > + ) -> Result { > + 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(), > + }; I suppose other than platform drivers, I2C drivers can't match by name, hen= ce I think we should fail if none of the above is provided. > + > + // SAFETY: It's safe to set the fields of `struct i2c_client` on= initialization. > + unsafe { > + (*pdrv.get()).driver.name =3D name.as_char_ptr(); > + (*pdrv.get()).probe =3D Some(Self::probe_callback); > + (*pdrv.get()).remove =3D Some(Self::remove_callback); > + (*pdrv.get()).shutdown =3D Some(Self::shutdown_callback); > + (*pdrv.get()).id_table =3D i2c_table; > + (*pdrv.get()).driver.of_match_table =3D of_table; > + (*pdrv.get()).driver.acpi_match_table =3D acpi_table; > + } > + > + // SAFETY: `pdrv` is guaranteed to be a valid `RegType`. > + to_result(unsafe { bindings::i2c_register_driver(module.0, pdrv.= get()) }) > + } > + > + unsafe fn unregister(pdrv: &Opaque) { > + // SAFETY: `pdrv` is guaranteed to be a valid `RegType`. > + unsafe { bindings::i2c_del_driver(pdrv.get()) } > + } > +} > + > +impl Adapter { > + extern "C" fn probe_callback(pdev: *mut bindings::i2c_client) -> ker= nel::ffi::c_int { > + // SAFETY: The I2C bus only ever calls the probe callback with a= valid pointer to a > + // `struct i2c_client`. > + // > + // INVARIANT: `pdev` is valid for the duration of `probe_callbac= k()`. > + let pdev =3D unsafe { &*pdev.cast::= >() }; > + > + let info =3D > + Self::i2c_id_info(pdev).or_else(|| = ::id_info(pdev.as_ref())); > + > + > + from_result(|| { > + let data =3D T::probe(pdev, info)?; > + > + pdev.as_ref().set_drvdata(data); > + Ok(0) > + }) > + } > + > + extern "C" fn remove_callback(pdev: *mut bindings::i2c_client) { > + // SAFETY: `pdev` is a valid pointer to a `struct i2c_client`. > + let pdev =3D unsafe { &*pdev.cast::= >() }; > + > + // SAFETY: `remove_callback` is only ever called after a success= ful call to > + // `probe_callback`, hence it's guaranteed that `Device::set_drv= data()` has been called > + // and stored a `Pin>`. > + drop(unsafe { pdev.as_ref().drvdata_obtain::>>() }); > + } > + > + extern "C" fn shutdown_callback(pdev: *mut bindings::i2c_client) { > + let pdev =3D unsafe { &*pdev.cast::>() }; Missing safety comment, please make sure to compile with CLIPPY=3D1. I thin= k I also saw some checkpatch.pl warnings. > + > + T::shutdown(pdev); > + } > + > + /// The [`i2c::IdTable`] of the corresponding driver. > + fn i2c_id_table() -> Option::IdInf= o>> { > + 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: &Device) -> Option<&'static ::IdInfo> { > + let table =3D Self::i2c_id_table()?; > + > + // SAFETY: > + // - `table` has static lifetime, hence it's valid for read, > + // - `dev` is guaranteed to be valid while it's alive, and so is= `pdev.as_ref().as_raw()`. > + let raw_id =3D unsafe { bindings::i2c_match_id(table.as_ptr(), d= ev.as_raw()) }; > + > + if raw_id.is_null() { > + None > + } else { > + // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of = `struct i2c_device_id` and > + // does not add additional invariants, so it's safe to trans= mute. > + 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 regis= tered. > +/// > +/// # 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(= &I2C_TABLE); > +/// const OF_ID_TABLE: Option> =3D Some(&O= F_TABLE); > +/// const ACPI_ID_TABLE: Option> =3D Som= e(&ACPI_TABLE); > +/// > +/// fn probe( > +/// _pdev: &i2c::Device, > +/// _id_info: Option<&Self::IdInfo>, > +/// ) -> Result>> { > +/// Err(ENODEV) > +/// } > +/// > +/// fn shutdown(_pdev: &i2c::Device) { > +/// } > +/// } > +///``` > +pub trait Driver: Send { > + /// The type holding information about each device id supported by t= he 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 device is added or discovered. > + /// Implementers should attempt to initialize the device here. > + fn probe(dev: &Device, id_info: Option<&Self::IdInfo>) > + -> Result>>; > + > + /// I2C driver shutdown > + /// > + /// Called when Yes? :) > + fn shutdown(dev: &Device) { > + let _ =3D dev; > + } > +} > + > +/// The i2c client representation. > +/// > +/// This structure represents the Rust abstraction for a C `struct i2c_c= lient`. The > +/// implementation abstracts the usage of an already existing C `struct = i2c_client` within Rust > +/// code that we get passed from the C side. > +/// > +/// # Invariants > +/// > +/// A [`Device`] instance represents a valid `struct i2c_client` created= by the C portion of > +/// the kernel. > +#[repr(transparent)] > +pub struct Device( > + Opaque, > + PhantomData, > +); > + > +impl Device { > + fn as_raw(&self) -> *mut bindings::i2c_client { > + self.0.get() > + } > +} > + > +// SAFETY: `Device` is a transparent wrapper of a type that doesn't depe= nd on `Device`'s generic > +// argument. > +kernel::impl_device_context_deref!(unsafe { Device }); > +kernel::impl_device_context_into_aref!(Device); > + > +// SAFETY: Instances of `Device` are always reference-counted. > +unsafe impl crate::types::AlwaysRefCounted for Device { > + fn inc_ref(&self) { > + // SAFETY: The existence of a shared reference guarantees that t= he 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 i= s non-zero. > + unsafe { bindings::put_device(addr_of_mut!((*obj.as_ref().as_raw= ()).dev)) } You can also use &raw mut. > + } > +} > + > +impl AsRef> for Device { > + fn as_ref(&self) -> &device::Device { > + // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a= pointer to a valid > + // `struct i2c_client`. > + let dev =3D unsafe { addr_of_mut!((*self.as_raw()).dev) }; Same here. > + > + // SAFETY: `dev` points to a valid `struct device`. > + unsafe { device::Device::from_raw(dev) } > + } > +} > + > +impl TryFrom<&device::Device> for &Devi= ce { > + 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 pdev =3D unsafe { container_of!(dev.as_raw(), bindings::i2c_= client, dev) }; > + > + // SAFETY: `pdev` is a valid pointer to a `struct i2c_client`. > + Ok(unsafe { &*pdev.cast() }) > + } > +} > + > +// SAFETY: A `Device` is always reference-counted and can be released fr= om any thread. > +unsafe impl Send for Device {} > + > +// SAFETY: `Device` can be shared among threads because all methods of `= Device` > +// (i.e. `Device) are thread safe. > +unsafe impl Sync for Device {} > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs > index c2d1b9375205..0780c3e746fc 100644 > --- a/rust/kernel/lib.rs > +++ b/rust/kernel/lib.rs > @@ -86,6 +86,8 @@ > #[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)] > pub mod firmware; > pub mod fs; > +#[cfg(CONFIG_I2C =3D "y")] > +pub mod i2c; > pub mod init; > pub mod io; > pub mod ioctl; > --=20 > 2.43.0