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Sat, 06 Dec 2025 19:33:53 -0800 (PST) Received: from nyaos.localdomain ([166.0.199.48]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-bf6a1caeea7sm8496390a12.24.2025.12.06.19.33.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 06 Dec 2025 19:33:53 -0800 (PST) From: ChenMiao To: zhao1.liu@intel.com, pbonzini@redhat.com, manos.pitsidianakis@linaro.org, richard.henderson@linaro.org, philmd@linaro.org Cc: chao.liu@openatom.club , dzm91@openatom.club , qemu-rust@nongnu.org, qemu-devel@nongnu.org, hust-os-kernel-patches@googlegroups.com, chenmiao Subject: [PATCH v3 2/4] rust/hw/core: Add rust bindings/funcs for i2c bus Date: Sun, 7 Dec 2025 03:33:29 +0000 Message-ID: <48bfe2bd3b11f09bd501622370ca64bdb1f68afb.1765077679.git.chenmiao@openatom.club> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::429; envelope-from=chenmiao.ku@gmail.com; helo=mail-pf1-x429.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Sat, 06 Dec 2025 23:34:06 -0500 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: chenmiao We have implemented the I2CBus and I2CSlave infrastructure in Rust by referring to the SysBus device model. Initially, we assumed that the I2CBus was at the same hierarchical level as the PL011 device. Therefore, we followed the implementation paradigm of the PL011 device as a reference. However, in the end, we discovered that the I2CBus is actually at the same level as the SysBus. As a result, we adopted the binding implementation paradigm used for SysBus devices. With this adjustment, we successfully compiled the code locally. During the implementation process, we found that the current two paradigms in Rust — bindings and impl — are extremely complex and lack comprehensive documentation. There is no clear explanation as to why Bus and Device models need to be implemented using different approaches. Furthermore, the implementation of Bus and Device following these paradigms still has many limitations. At present, at least vmstate is not easily supported. Signed-off-by: Chao Liu Signed-off-by: Chen Miao --- rust/hw/core/meson.build | 1 + rust/hw/core/src/i2c.rs | 303 +++++++++++++++++++++++++++++++++++++++ rust/hw/core/src/lib.rs | 3 + rust/hw/core/wrapper.h | 1 + 4 files changed, 308 insertions(+) create mode 100644 rust/hw/core/src/i2c.rs diff --git a/rust/hw/core/meson.build b/rust/hw/core/meson.build index efcda50fef..1a27c1cff7 100644 --- a/rust/hw/core/meson.build +++ b/rust/hw/core/meson.build @@ -52,6 +52,7 @@ _hwcore_rs = static_library( 'src/bindings.rs', 'src/bus.rs', 'src/irq.rs', + 'src/i2c.rs', 'src/qdev.rs', 'src/sysbus.rs', ], diff --git a/rust/hw/core/src/i2c.rs b/rust/hw/core/src/i2c.rs new file mode 100644 index 0000000000..85ec34357a --- /dev/null +++ b/rust/hw/core/src/i2c.rs @@ -0,0 +1,303 @@ +// Copyright 2025 HUST OpenAtom Open Source Club. +// Author(s): Chao Liu +// Author(s): Chen Miao +// SPDX-License-Identifier: GPL-2.0-or-later + +//! Bindings to access `i2c` functionality from Rust. + +use std::{ffi::CStr, ptr::NonNull}; + +pub use crate::bindings::I2CSlaveClass; +use common::{self, Opaque}; +use migration::impl_vmstate_c_struct; +use qom::{prelude::*, Owned}; + +use crate::{ + bindings, + bus::{BusClass, BusState}, + qdev::{DeviceImpl, DeviceState}, +}; + +/// A safe wrapper around [`bindings::I2CBus`]. +#[repr(transparent)] +#[derive(Debug, common::Wrapper)] +pub struct I2CBus(Opaque); + +unsafe impl Send for I2CBus {} +unsafe impl Sync for I2CBus {} + +unsafe impl ObjectType for I2CBus { + type Class = BusClass; + const TYPE_NAME: &'static CStr = + unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_I2C_BUS) }; +} + +qom_isa!(I2CBus: BusState, Object); + +/// Trait for methods of [`I2CBus`] and its subclasses. +pub trait I2CBusMethods: ObjectDeref +where + Self::Target: IsA, +{ + /// # Safety + /// + /// Initialize an I2C bus + fn init_bus(&self, parent: &DeviceState, name: &str) -> Owned { + assert!(bql::is_locked()); + unsafe { + let bus = bindings::i2c_init_bus(parent.as_mut_ptr(), name.as_ptr().cast()); + let bus: &I2CBus = I2CBus::from_raw(bus); + Owned::from(bus) + } + } + + /// # Safety + /// + /// Start a transfer on an I2C bus + fn start_transfer(&self, address: u8, is_recv: bool) -> i32 { + assert!(bql::is_locked()); + unsafe { bindings::i2c_start_transfer(self.upcast().as_mut_ptr(), address, is_recv) } + } + + /// # Safety + /// + /// Start a receive transfer on an I2C bus + fn start_recv(&self, address: u8) -> i32 { + assert!(bql::is_locked()); + unsafe { bindings::i2c_start_recv(self.upcast().as_mut_ptr(), address) } + } + + /// # Safety + /// + /// Start a send transfer on an I2C bus + fn start_send(&self, address: u8) -> i32 { + assert!(bql::is_locked()); + unsafe { bindings::i2c_start_send(self.upcast().as_mut_ptr(), address) } + } + + /// # Safety + /// + /// End a transfer on an I2C bus + fn end_transfer(&self) { + assert!(bql::is_locked()); + unsafe { bindings::i2c_end_transfer(self.upcast().as_mut_ptr()) } + } + + /// # Safety + /// + /// Send NACK on an I2C bus + fn nack(&self) { + assert!(bql::is_locked()); + unsafe { bindings::i2c_nack(self.upcast().as_mut_ptr()) } + } + + /// # Safety + /// + /// Send ACK on an I2C bus + fn ack(&self) { + assert!(bql::is_locked()); + unsafe { bindings::i2c_ack(self.upcast().as_mut_ptr()) } + } + + /// # Safety + /// + /// Send data on an I2C bus + fn send(&self, data: u8) -> i32 { + assert!(bql::is_locked()); + unsafe { bindings::i2c_send(self.upcast().as_mut_ptr(), data) } + } + + /// # Safety + /// + /// Receive data from an I2C bus + fn recv(&self) -> u8 { + assert!(bql::is_locked()); + unsafe { bindings::i2c_recv(self.upcast().as_mut_ptr()) } + } + + /// # Safety + /// + /// Check if the I2C bus is busy. + /// + /// Returns `true` if the bus is busy, `false` otherwise. + fn is_busy(&self) -> bool { + assert!(bql::is_locked()); + unsafe { bindings::i2c_bus_busy(self.upcast().as_mut_ptr()) != 0 } + } + + /// # Safety + /// + /// Schedule pending master on an I2C bus + fn schedule_pending_master(&self) { + assert!(bql::is_locked()); + unsafe { bindings::i2c_schedule_pending_master(self.upcast().as_mut_ptr()) } + } + + /// Sets the I2C bus master. + /// + /// # Safety + /// + /// This function is unsafe because: + /// - `bh` must be a valid pointer to a `QEMUBH`. + /// - The caller must ensure that `self` is in a valid state. + /// - The caller must guarantee no data races occur during execution. + /// + /// TODO ("`i2c_bus_master` missing until QEMUBH is wrapped") + unsafe fn set_master(&self, bh: *mut bindings::QEMUBH) { + assert!(bql::is_locked()); + unsafe { bindings::i2c_bus_master(self.upcast().as_mut_ptr(), bh) } + } +} + +impl I2CBusMethods for R where R::Target: IsA {} + +/// A safe wrapper around [`bindings::I2CSlave`]. +#[repr(transparent)] +#[derive(Debug, common::Wrapper)] +pub struct I2CSlave(Opaque); + +unsafe impl Send for I2CSlave {} +unsafe impl Sync for I2CSlave {} + +unsafe impl ObjectType for I2CSlave { + type Class = I2CSlaveClass; + const TYPE_NAME: &'static CStr = + unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_I2C_SLAVE) }; +} + +qom_isa!(I2CSlave: DeviceState, Object); + +impl_vmstate_c_struct!(I2CSlave, bindings::vmstate_i2c_slave); + +#[derive(common::TryInto)] +#[repr(u64)] +#[allow(non_camel_case_types)] +pub enum I2CResult { + ACK = 0, + NACK = 1, +} + +// TODO: add virtual methods +pub trait I2CSlaveImpl: DeviceImpl + IsA { + /// Master to slave. Returns non-zero for a NAK, 0 for success. + const SEND: Option I2CResult> = None; + + /// Slave to master. This cannot fail, the device should always return something here. + const RECV: Option u8> = None; + + /// Notify the slave of a bus state change. For start event, + /// returns non-zero to NAK an operation. For other events the + /// return code is not used and should be zero. + const EVENT: Option I2CEvent> = None; + + /// Check if this device matches the address provided. Returns bool of + /// true if it matches (or broadcast), and updates the device list, false + /// otherwise. + /// + /// If broadcast is true, match should add the device and return true. + #[allow(clippy::type_complexity)] + const MATCH_AND_ADD: Option< + fn(&Self, address: u8, broadcast: bool, current_devs: *mut bindings::I2CNodeList) -> bool, + > = None; +} + +/// # Safety +/// +/// We expect the FFI user of this function to pass a valid pointer that +/// can be downcasted to type `T`. We also expect the device is +/// readable/writeable from one thread at any time. +unsafe extern "C" fn rust_i2c_slave_send_fn( + obj: *mut bindings::I2CSlave, + data: u8, +) -> std::os::raw::c_int { + let state = NonNull::new(obj).unwrap().cast::(); + T::SEND.unwrap()(unsafe { state.as_ref() }, data).into_bits() as std::os::raw::c_int +} + +/// # Safety +/// +/// We expect the FFI user of this function to pass a valid pointer that +/// can be downcasted to type `T`. We also expect the device is +/// readable/writeable from one thread at any time. +unsafe extern "C" fn rust_i2c_slave_recv_fn(obj: *mut bindings::I2CSlave) -> u8 { + let state = NonNull::new(obj).unwrap().cast::(); + T::RECV.unwrap()(unsafe { state.as_ref() }) +} + +/// # Safety +/// +/// We expect the FFI user of this function to pass a valid pointer that +/// can be downcasted to type `T`. We also expect the device is +/// readable/writeable from one thread at any time. +unsafe extern "C" fn rust_i2c_slave_event_fn( + obj: *mut bindings::I2CSlave, + event: bindings::i2c_event, +) -> std::os::raw::c_int { + let state = NonNull::new(obj).unwrap().cast::(); + T::EVENT.unwrap()(unsafe { state.as_ref() }, I2CEvent::from_bits(event)).into_bits() + as std::os::raw::c_int +} + +/// # Safety +/// +/// We expect the FFI user of this function to pass a valid pointer that +/// can be downcasted to type `T`. We also expect the device is +/// readable/writeable from one thread at any time. +unsafe extern "C" fn rust_i2c_slave_match_and_add_fn( + obj: *mut bindings::I2CSlave, + address: u8, + broadcast: bool, + current_devs: *mut bindings::I2CNodeList, +) -> bool { + let state = NonNull::new(obj).unwrap().cast::(); + T::MATCH_AND_ADD.unwrap()(unsafe { state.as_ref() }, address, broadcast, current_devs) +} + +impl I2CSlaveClass { + /// Fill in the virtual methods of `I2CSlaveClass` based on the + /// definitions in the `I2CSlaveImpl` trait. + pub fn class_init(&mut self) { + if ::SEND.is_some() { + self.send = Some(rust_i2c_slave_send_fn::); + } + if ::RECV.is_some() { + self.recv = Some(rust_i2c_slave_recv_fn::); + } + if ::EVENT.is_some() { + self.event = Some(rust_i2c_slave_event_fn::); + } + if ::MATCH_AND_ADD.is_some() { + self.match_and_add = Some(rust_i2c_slave_match_and_add_fn::); + } + self.parent_class.class_init::(); + } +} + +/// Trait for methods of [`I2CSlave`] and its subclasses. +pub trait I2CSlaveMethods: ObjectDeref +where + Self::Target: IsA, +{ + /// Get the I2C bus address of a slave device + fn get_address(&self) -> u8 { + assert!(bql::is_locked()); + // SAFETY: the BQL ensures that no one else writes to the I2CSlave structure, + // and the I2CSlave must be initialized to get an IsA. + let slave = unsafe { *self.upcast().as_ptr() }; + slave.address + } +} + +impl I2CSlaveMethods for R where R::Target: IsA {} + +/// Enum representing I2C events +#[derive(common::TryInto)] +#[repr(u32)] +#[allow(non_camel_case_types)] +pub enum I2CEvent { + START_RECV = bindings::I2C_START_RECV, + START_SEND = bindings::I2C_START_SEND, + START_SEND_ASYNC = bindings::I2C_START_SEND_ASYNC, + FINISH = bindings::I2C_FINISH, + NACK = bindings::I2C_NACK, +} diff --git a/rust/hw/core/src/lib.rs b/rust/hw/core/src/lib.rs index 10cc516664..3f3aecb258 100644 --- a/rust/hw/core/src/lib.rs +++ b/rust/hw/core/src/lib.rs @@ -16,3 +16,6 @@ mod bus; pub use bus::*; + +mod i2c; +pub use i2c::*; diff --git a/rust/hw/core/wrapper.h b/rust/hw/core/wrapper.h index 3bdbd1249e..399be594da 100644 --- a/rust/hw/core/wrapper.h +++ b/rust/hw/core/wrapper.h @@ -30,3 +30,4 @@ typedef enum memory_order { #include "hw/qdev-properties.h" #include "hw/qdev-properties-system.h" #include "hw/irq.h" +#include "hw/i2c/i2c.h" -- 2.43.0