[RFC PATCH v2 1/5] rust/hw/core: Add the BusState of rust version

["chenmiao" <chenmiao@openatom.club>]

A Rust version implementation has been designed for BusState,
which will be used for the subsequent I2CBus implementation.

Signed-off-by: chenmiao <chenmiao@openatom.club>
Signed-off-by: Chao Liu <chao.liu@openatom.club>

---
Changes in V2:
  - Rename the BusMethods and add some Safety comment.
  - Remove the unnecessary realize function.

---
 rust/hw/core/meson.build |  1 +
 rust/hw/core/src/bus.rs  | 44 ++++++++++++++++++++++++++++++++++++++++
 rust/hw/core/src/lib.rs  |  3 +++
 3 files changed, 48 insertions(+)
 create mode 100644 rust/hw/core/src/bus.rs

diff --git a/rust/hw/core/meson.build b/rust/hw/core/meson.build
index 1560dd20c6..efcda50fef 100644
--- a/rust/hw/core/meson.build
+++ b/rust/hw/core/meson.build
@@ -50,6 +50,7 @@ _hwcore_rs = static_library(
     [
       'src/lib.rs',
       'src/bindings.rs',
+      'src/bus.rs',
       'src/irq.rs',
       'src/qdev.rs',
       'src/sysbus.rs',
diff --git a/rust/hw/core/src/bus.rs b/rust/hw/core/src/bus.rs
new file mode 100644
index 0000000000..d3fbf519d4
--- /dev/null
+++ b/rust/hw/core/src/bus.rs
@@ -0,0 +1,44 @@
+// Copyright 2025 HUST OpenAtom Open Source Club.
+// Author(s): Chen Miao <chenmiao@openatom.club>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+use std::ffi::CStr;
+
+pub use bindings::BusClass;
+use common::Opaque;
+use qom::{qom_isa, IsA, Object, ObjectDeref, ObjectType};
+
+use crate::{bindings, DeviceImpl};
+
+#[repr(transparent)]
+#[derive(Debug, common::Wrapper)]
+pub struct BusState(Opaque<bindings::BusState>);
+
+unsafe impl Send for BusState {}
+unsafe impl Sync for BusState {}
+
+unsafe impl ObjectType for BusState {
+    type Class = BusClass;
+    const TYPE_NAME: &'static std::ffi::CStr =
+        unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_BUS) };
+}
+
+qom_isa!(BusState: Object);
+
+pub trait BusStateImpl: DeviceImpl + IsA<BusState> {}
+
+impl BusClass {
+    pub fn class_init<T: BusStateImpl>(self: &mut BusClass) {
+        self.parent_class.class_init::<T>();
+    }
+}
+
+pub trait BusMethods: ObjectDeref
+where
+    Self::Target: IsA<BusState>,
+{
+    // TODO: Since the bus does not currently provide services to other
+    // components, we have not implemented any functions yet.
+}
+
+impl<R: ObjectDeref> BusMethods for R where R::Target: IsA<BusState> {}
diff --git a/rust/hw/core/src/lib.rs b/rust/hw/core/src/lib.rs
index b40801eb84..10cc516664 100644
--- a/rust/hw/core/src/lib.rs
+++ b/rust/hw/core/src/lib.rs
@@ -13,3 +13,6 @@
 
 mod sysbus;
 pub use sysbus::*;
+
+mod bus;
+pub use bus::*;
-- 
2.43.0