Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging

* scripts: dump stdin on meson-buildoptions error
* rust: introduce qemu_api::cell::Opaque<>
* rust: express pinning requirements for timers
* rust: hpet: decode HPET registers into enums
* rust: cell: add full example of declaring a SysBusDevice
* rust: qom: remove operations on &mut

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# gpg: Signature made Sun 09 Mar 2025 18:29:16 HKT
# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
# gpg:                issuer "pbonzini@redhat.com"
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full]
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>" [full]
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* tag 'for-upstream' of https://gitlab.com/bonzini/qemu: (25 commits)
  rust: pl011: Allow NULL chardev argument to pl011_create()
  meson.build: default to -gsplit-dwarf for debug info
  rust: qom: remove operations on &mut
  rust: cell: add full example of declaring a SysBusDevice
  rust: hpet: decode HPET registers into enums
  rust: pl011: pass around registers::Data
  rust: pl011: switch to safe chardev operation
  rust: pl011: clean up visibilities of callbacks
  rust: pl011: move register definitions out of lib.rs
  rust: chardev: provide basic bindings to character devices
  rust: bindings: remove more unnecessary Send/Sync impls
  rust: chardev: wrap Chardev with Opaque<>
  rust: memory: wrap MemoryRegion with Opaque<>
  rust: sysbus: wrap SysBusDevice with Opaque<>
  rust: hpet: do not access fields of SysBusDevice
  rust: qdev: wrap Clock and DeviceState with Opaque<>
  rust: qom: wrap Object with Opaque<>
  rust: irq: wrap IRQState with Opaque<>
  rust: timer: wrap QEMUTimer with Opaque<> and express pinning requirements
  rust: hpet: embed Timer without the Option and Box indirection
  ...

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

14 files changed, 708 insertions, 233 deletions

diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index bcf1cf7..a3f226c 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -42,22 +42,31 @@ _qemu_api_rs = static_library(
   override_options: ['rust_std=2021', 'build.rust_std=2021'],
   rust_abi: 'rust',
   rust_args: _qemu_api_cfg,
-  dependencies: libc_dep,
+  dependencies: [libc_dep, qemu_api_macros],
 )
 
 rust.test('rust-qemu-api-tests', _qemu_api_rs,
           suite: ['unit', 'rust'])
 
-qemu_api = declare_dependency(
-  link_with: _qemu_api_rs,
-  dependencies: qemu_api_macros,
-)
+qemu_api = declare_dependency(link_with: _qemu_api_rs)
 
 # Rust executables do not support objects, so add an intermediate step.
 rust_qemu_api_objs = static_library(
     'rust_qemu_api_objs',
     objects: [libqom.extract_all_objects(recursive: false),
-              libhwcore.extract_all_objects(recursive: false)])
+              libhwcore.extract_all_objects(recursive: false),
+              libchardev.extract_all_objects(recursive: false),
+              libcrypto.extract_all_objects(recursive: false),
+              libauthz.extract_all_objects(recursive: false),
+              libio.extract_all_objects(recursive: false)])
+rust_qemu_api_deps = declare_dependency(
+    dependencies: [
+      qom_ss.dependencies(),
+      chardev_ss.dependencies(),
+      crypto_ss.dependencies(),
+      authz_ss.dependencies(),
+      io_ss.dependencies()],
+    link_whole: [rust_qemu_api_objs, libqemuutil])
 
 test('rust-qemu-api-integration',
     executable(
@@ -66,8 +75,7 @@ test('rust-qemu-api-integration',
         override_options: ['rust_std=2021', 'build.rust_std=2021'],
         rust_args: ['--test'],
         install: false,
-        dependencies: [qemu_api, qemu_api_macros],
-        link_whole: [rust_qemu_api_objs, libqemuutil]),
+        dependencies: [qemu_api, qemu_api_macros, rust_qemu_api_deps]),
     args: [
         '--test', '--test-threads', '1',
         '--format', 'pretty',
diff --git a/rust/qemu-api/src/bindings.rs b/rust/qemu-api/src/bindings.rs
index d286863..3c1d297 100644
--- a/rust/qemu-api/src/bindings.rs
+++ b/rust/qemu-api/src/bindings.rs
@@ -25,33 +25,11 @@ include!(concat!(env!("OUT_DIR"), "/bindings.inc.rs"));
 
 // SAFETY: these are implemented in C; the bindings need to assert that the
 // BQL is taken, either directly or via `BqlCell` and `BqlRefCell`.
-unsafe impl Send for BusState {}
-unsafe impl Sync for BusState {}
-
+// When bindings for character devices are introduced, this can be
+// moved to the Opaque<> wrapper in src/chardev.rs.
 unsafe impl Send for CharBackend {}
 unsafe impl Sync for CharBackend {}
 
-unsafe impl Send for Chardev {}
-unsafe impl Sync for Chardev {}
-
-unsafe impl Send for Clock {}
-unsafe impl Sync for Clock {}
-
-unsafe impl Send for DeviceState {}
-unsafe impl Sync for DeviceState {}
-
-unsafe impl Send for MemoryRegion {}
-unsafe impl Sync for MemoryRegion {}
-
-unsafe impl Send for ObjectClass {}
-unsafe impl Sync for ObjectClass {}
-
-unsafe impl Send for Object {}
-unsafe impl Sync for Object {}
-
-unsafe impl Send for SysBusDevice {}
-unsafe impl Sync for SysBusDevice {}
-
 // SAFETY: this is a pure data struct
 unsafe impl Send for CoalescedMemoryRange {}
 unsafe impl Sync for CoalescedMemoryRange {}
diff --git a/rust/qemu-api/src/cell.rs b/rust/qemu-api/src/cell.rs
index eae4e2c..ab0785a 100644
--- a/rust/qemu-api/src/cell.rs
+++ b/rust/qemu-api/src/cell.rs
@@ -27,7 +27,7 @@
 // IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-//! BQL-protected mutable containers.
+//! QEMU-specific mutable containers
 //!
 //! Rust memory safety is based on this rule: Given an object `T`, it is only
 //! possible to have one of the following:
@@ -43,8 +43,10 @@
 //! usually have their pointer shared with the "outside world very early in
 //! their lifetime", for example when they create their
 //! [`MemoryRegion`s](crate::bindings::MemoryRegion).  Therefore, individual
-//! parts of a  device must be made mutable in a controlled manner through the
-//! use of cell types.
+//! parts of a  device must be made mutable in a controlled manner; this module
+//! provides the tools to do so.
+//!
+//! ## Cell types
 //!
 //! [`BqlCell<T>`] and [`BqlRefCell<T>`] allow doing this via the Big QEMU Lock.
 //! While they are essentially the same single-threaded primitives that are
@@ -71,7 +73,35 @@
 //! QEMU device implementations is usually incorrect and can lead to
 //! thread-safety issues.
 //!
-//! ## `BqlCell<T>`
+//! ### Example
+//!
+//! ```
+//! # use qemu_api::prelude::*;
+//! # use qemu_api::{c_str, cell::BqlRefCell, irq::InterruptSource, irq::IRQState};
+//! # use qemu_api::{sysbus::SysBusDevice, qom::Owned, qom::ParentField};
+//! # const N_GPIOS: usize = 8;
+//! # struct PL061Registers { /* ... */ }
+//! # unsafe impl ObjectType for PL061State {
+//! #     type Class = <SysBusDevice as ObjectType>::Class;
+//! #     const TYPE_NAME: &'static std::ffi::CStr = c_str!("pl061");
+//! # }
+//! struct PL061State {
+//!     parent_obj: ParentField<SysBusDevice>,
+//!
+//!     // Configuration is read-only after initialization
+//!     pullups: u32,
+//!     pulldowns: u32,
+//!
+//!     // Single values shared with C code use BqlCell, in this case via InterruptSource
+//!     out: [InterruptSource; N_GPIOS],
+//!     interrupt: InterruptSource,
+//!
+//!     // Larger state accessed by device methods uses BqlRefCell or Mutex
+//!     registers: BqlRefCell<PL061Registers>,
+//! }
+//! ```
+//!
+//! ### `BqlCell<T>`
 //!
 //! [`BqlCell<T>`] implements interior mutability by moving values in and out of
 //! the cell. That is, an `&mut T` to the inner value can never be obtained as
@@ -91,7 +121,7 @@
 //!    - [`set`](BqlCell::set): this method replaces the interior value,
 //!      dropping the replaced value.
 //!
-//! ## `BqlRefCell<T>`
+//! ### `BqlRefCell<T>`
 //!
 //! [`BqlRefCell<T>`] uses Rust's lifetimes to implement "dynamic borrowing", a
 //! process whereby one can claim temporary, exclusive, mutable access to the
@@ -111,13 +141,82 @@
 //! Multiple immutable borrows are allowed via [`borrow`](BqlRefCell::borrow),
 //! or a single mutable borrow via [`borrow_mut`](BqlRefCell::borrow_mut).  The
 //! thread will panic if these rules are violated or if the BQL is not held.
+//!
+//! ## Opaque wrappers
+//!
+//! The cell types from the previous section are useful at the boundaries
+//! of code that requires interior mutability.  When writing glue code that
+//! interacts directly with C structs, however, it is useful to operate
+//! at a lower level.
+//!
+//! C functions often violate Rust's fundamental assumptions about memory
+//! safety by modifying memory even if it is shared.  Furthermore, C structs
+//! often start their life uninitialized and may be populated lazily.
+//!
+//! For this reason, this module provides the [`Opaque<T>`] type to opt out
+//! of Rust's usual guarantees about the wrapped type. Access to the wrapped
+//! value is always through raw pointers, obtained via methods like
+//! [`as_mut_ptr()`](Opaque::as_mut_ptr) and [`as_ptr()`](Opaque::as_ptr). These
+//! pointers can then be passed to C functions or dereferenced; both actions
+//! require `unsafe` blocks, making it clear where safety guarantees must be
+//! manually verified. For example
+//!
+//! ```ignore
+//! unsafe {
+//!     let state = Opaque::<MyStruct>::uninit();
+//!     qemu_struct_init(state.as_mut_ptr());
+//! }
+//! ```
+//!
+//! [`Opaque<T>`] will usually be wrapped one level further, so that
+//! bridge methods can be added to the wrapper:
+//!
+//! ```ignore
+//! pub struct MyStruct(Opaque<bindings::MyStruct>);
+//!
+//! impl MyStruct {
+//!     fn new() -> Pin<Box<MyStruct>> {
+//!         let result = Box::pin(unsafe { Opaque::uninit() });
+//!         unsafe { qemu_struct_init(result.as_mut_ptr()) };
+//!         result
+//!     }
+//! }
+//! ```
+//!
+//! This pattern of wrapping bindgen-generated types in [`Opaque<T>`] provides
+//! several advantages:
+//!
+//! * The choice of traits to be implemented is not limited by the
+//!   bindgen-generated code.  For example, [`Drop`] can be added without
+//!   disabling [`Copy`] on the underlying bindgen type
+//!
+//! * [`Send`] and [`Sync`] implementations can be controlled by the wrapper
+//!   type rather than being automatically derived from the C struct's layout
+//!
+//! * Methods can be implemented in a separate crate from the bindgen-generated
+//!   bindings
+//!
+//! * [`Debug`](std::fmt::Debug) and [`Display`](std::fmt::Display)
+//!   implementations can be customized to be more readable than the raw C
+//!   struct representation
+//!
+//! The [`Opaque<T>`] type does not include BQL validation; it is possible to
+//! assert in the code that the right lock is taken, to use it together
+//! with a custom lock guard type, or to let C code take the lock, as
+//! appropriate.  It is also possible to use it with non-thread-safe
+//! types, since by default (unlike [`BqlCell`] and [`BqlRefCell`]
+//! it is neither `Sync` nor `Send`.
+//!
+//! While [`Opaque<T>`] is necessary for C interop, it should be used sparingly
+//! and only at FFI boundaries. For QEMU-specific types that need interior
+//! mutability, prefer [`BqlCell`] or [`BqlRefCell`].
 
 use std::{
     cell::{Cell, UnsafeCell},
     cmp::Ordering,
     fmt,
-    marker::PhantomData,
-    mem,
+    marker::{PhantomData, PhantomPinned},
+    mem::{self, MaybeUninit},
     ops::{Deref, DerefMut},
     ptr::NonNull,
 };
@@ -840,3 +939,167 @@ impl<T: fmt::Display> fmt::Display for BqlRefMut<'_, T> {
         (**self).fmt(f)
     }
 }
+
+/// Stores an opaque value that is shared with C code.
+///
+/// Often, C structs can changed when calling a C function even if they are
+/// behind a shared Rust reference, or they can be initialized lazily and have
+/// invalid bit patterns (e.g. `3` for a [`bool`]).  This goes against Rust's
+/// strict aliasing rules, which normally prevent mutation through shared
+/// references.
+///
+/// Wrapping the struct with `Opaque<T>` ensures that the Rust compiler does not
+/// assume the usual constraints that Rust structs require, and allows using
+/// shared references on the Rust side.
+///
+/// `Opaque<T>` is `#[repr(transparent)]`, so that it matches the memory layout
+/// of `T`.
+#[repr(transparent)]
+pub struct Opaque<T> {
+    value: UnsafeCell<MaybeUninit<T>>,
+    // PhantomPinned also allows multiple references to the `Opaque<T>`, i.e.
+    // one `&mut Opaque<T>` can coexist with a `&mut T` or any number of `&T`;
+    // see https://docs.rs/pinned-aliasable/latest/pinned_aliasable/.
+    _pin: PhantomPinned,
+}
+
+impl<T> Opaque<T> {
+    /// Creates a new shared reference from a C pointer
+    ///
+    /// # Safety
+    ///
+    /// The pointer must be valid, though it need not point to a valid value.
+    pub unsafe fn from_raw<'a>(ptr: *mut T) -> &'a Self {
+        let ptr = NonNull::new(ptr).unwrap().cast::<Self>();
+        // SAFETY: Self is a transparent wrapper over T
+        unsafe { ptr.as_ref() }
+    }
+
+    /// Creates a new opaque object with uninitialized contents.
+    ///
+    /// # Safety
+    ///
+    /// Ultimately the pointer to the returned value will be dereferenced
+    /// in another `unsafe` block, for example when passing it to a C function,
+    /// but the functions containing the dereference are usually safe.  The
+    /// value returned from `uninit()` must be initialized and pinned before
+    /// calling them.
+    #[allow(clippy::missing_const_for_fn)]
+    pub unsafe fn uninit() -> Self {
+        Self {
+            value: UnsafeCell::new(MaybeUninit::uninit()),
+            _pin: PhantomPinned,
+        }
+    }
+
+    /// Creates a new opaque object with zeroed contents.
+    ///
+    /// # Safety
+    ///
+    /// Ultimately the pointer to the returned value will be dereferenced
+    /// in another `unsafe` block, for example when passing it to a C function,
+    /// but the functions containing the dereference are usually safe.  The
+    /// value returned from `uninit()` must be pinned (and possibly initialized)
+    /// before calling them.
+    #[allow(clippy::missing_const_for_fn)]
+    pub unsafe fn zeroed() -> Self {
+        Self {
+            value: UnsafeCell::new(MaybeUninit::zeroed()),
+            _pin: PhantomPinned,
+        }
+    }
+
+    /// Returns a raw mutable pointer to the opaque data.
+    pub const fn as_mut_ptr(&self) -> *mut T {
+        UnsafeCell::get(&self.value).cast()
+    }
+
+    /// Returns a raw pointer to the opaque data.
+    pub const fn as_ptr(&self) -> *const T {
+        self.as_mut_ptr() as *const _
+    }
+
+    /// Returns a raw pointer to the opaque data that can be passed to a
+    /// C function as `void *`.
+    pub const fn as_void_ptr(&self) -> *mut std::ffi::c_void {
+        UnsafeCell::get(&self.value).cast()
+    }
+
+    /// Converts a raw pointer to the wrapped type.
+    pub const fn raw_get(slot: *mut Self) -> *mut T {
+        // Compare with Linux's raw_get method, which goes through an UnsafeCell
+        // because it takes a *const Self instead.
+        slot.cast()
+    }
+}
+
+impl<T> fmt::Debug for Opaque<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let mut name: String = "Opaque<".to_string();
+        name += std::any::type_name::<T>();
+        name += ">";
+        f.debug_tuple(&name).field(&self.as_ptr()).finish()
+    }
+}
+
+impl<T: Default> Opaque<T> {
+    /// Creates a new opaque object with default contents.
+    ///
+    /// # Safety
+    ///
+    /// Ultimately the pointer to the returned value will be dereferenced
+    /// in another `unsafe` block, for example when passing it to a C function,
+    /// but the functions containing the dereference are usually safe.  The
+    /// value returned from `uninit()` must be pinned before calling them.
+    pub unsafe fn new() -> Self {
+        Self {
+            value: UnsafeCell::new(MaybeUninit::new(T::default())),
+            _pin: PhantomPinned,
+        }
+    }
+}
+
+/// Annotates [`Self`] as a transparent wrapper for another type.
+///
+/// Usually defined via the [`qemu_api_macros::Wrapper`] derive macro.
+///
+/// # Examples
+///
+/// ```
+/// # use std::mem::ManuallyDrop;
+/// # use qemu_api::cell::Wrapper;
+/// #[repr(transparent)]
+/// pub struct Example {
+///     inner: ManuallyDrop<String>,
+/// }
+///
+/// unsafe impl Wrapper for Example {
+///     type Wrapped = String;
+/// }
+/// ```
+///
+/// # Safety
+///
+/// `Self` must be a `#[repr(transparent)]` wrapper for the `Wrapped` type,
+/// whether directly or indirectly.
+///
+/// # Methods
+///
+/// By convention, types that implement Wrapper also implement the following
+/// methods:
+///
+/// ```ignore
+/// pub const unsafe fn from_raw<'a>(value: *mut Self::Wrapped) -> &'a Self;
+/// pub const unsafe fn as_mut_ptr(&self) -> *mut Self::Wrapped;
+/// pub const unsafe fn as_ptr(&self) -> *const Self::Wrapped;
+/// pub const unsafe fn raw_get(slot: *mut Self) -> *const Self::Wrapped;
+/// ```
+///
+/// They are not defined here to allow them to be `const`.
+pub unsafe trait Wrapper {
+    type Wrapped;
+}
+
+unsafe impl<T> Wrapper for Opaque<T> {
+    type Wrapped = T;
+}
diff --git a/rust/qemu-api/src/chardev.rs b/rust/qemu-api/src/chardev.rs
index 74cfb63..11e6c45 100644
--- a/rust/qemu-api/src/chardev.rs
+++ b/rust/qemu-api/src/chardev.rs
@@ -3,13 +3,255 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 //! Bindings for character devices
+//!
+//! Character devices in QEMU can run under the big QEMU lock or in a separate
+//! `GMainContext`. Here we only support the former, because the bindings
+//! enforce that the BQL is taken whenever the functions in [`CharBackend`] are
+//! called.
 
-use std::ffi::CStr;
+use std::{
+    ffi::CStr,
+    fmt::{self, Debug},
+    io::{self, ErrorKind, Write},
+    marker::PhantomPinned,
+    os::raw::{c_int, c_void},
+    ptr::addr_of_mut,
+    slice,
+};
 
-use crate::{bindings, prelude::*};
+use crate::{
+    bindings,
+    callbacks::FnCall,
+    cell::{BqlRefMut, Opaque},
+    prelude::*,
+};
+
+/// A safe wrapper around [`bindings::Chardev`].
+#[repr(transparent)]
+#[derive(qemu_api_macros::Wrapper)]
+pub struct Chardev(Opaque<bindings::Chardev>);
 
-pub type Chardev = bindings::Chardev;
 pub type ChardevClass = bindings::ChardevClass;
+pub type Event = bindings::QEMUChrEvent;
+
+/// A safe wrapper around [`bindings::CharBackend`], denoting the character
+/// back-end that is used for example by a device.  Compared to the
+/// underlying C struct it adds BQL protection, and is marked as pinned
+/// because the QOM object ([`bindings::Chardev`]) contains a pointer to
+/// the `CharBackend`.
+pub struct CharBackend {
+    inner: BqlRefCell<bindings::CharBackend>,
+    _pin: PhantomPinned,
+}
+
+impl Write for BqlRefMut<'_, bindings::CharBackend> {
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        let chr: &mut bindings::CharBackend = self;
+
+        let len = buf.len().try_into().unwrap();
+        let r = unsafe { bindings::qemu_chr_fe_write(addr_of_mut!(*chr), buf.as_ptr(), len) };
+        errno::into_io_result(r).map(|cnt| cnt as usize)
+    }
+
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        let chr: &mut bindings::CharBackend = self;
+
+        let len = buf.len().try_into().unwrap();
+        let r = unsafe { bindings::qemu_chr_fe_write_all(addr_of_mut!(*chr), buf.as_ptr(), len) };
+        errno::into_io_result(r).and_then(|cnt| {
+            if cnt as usize == buf.len() {
+                Ok(())
+            } else {
+                Err(ErrorKind::WriteZero.into())
+            }
+        })
+    }
+}
+
+impl Debug for CharBackend {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // SAFETY: accessed just to print the values
+        let chr = self.inner.as_ptr();
+        Debug::fmt(unsafe { &*chr }, f)
+    }
+}
+
+// FIXME: use something like PinnedDrop from the pinned_init crate
+impl Drop for CharBackend {
+    fn drop(&mut self) {
+        self.disable_handlers();
+    }
+}
+
+impl CharBackend {
+    /// Enable the front-end's character device handlers, if there is an
+    /// associated `Chardev`.
+    pub fn enable_handlers<
+        'chardev,
+        'owner: 'chardev,
+        T,
+        CanReceiveFn: for<'a> FnCall<(&'a T,), u32>,
+        ReceiveFn: for<'a, 'b> FnCall<(&'a T, &'b [u8])>,
+        EventFn: for<'a> FnCall<(&'a T, Event)>,
+    >(
+        // When "self" is dropped, the handlers are automatically disabled.
+        // However, this is not necessarily true if the owner is dropped.
+        // So require the owner to outlive the character device.
+        &'chardev self,
+        owner: &'owner T,
+        _can_receive: CanReceiveFn,
+        _receive: ReceiveFn,
+        _event: EventFn,
+    ) {
+        unsafe extern "C" fn rust_can_receive_cb<T, F: for<'a> FnCall<(&'a T,), u32>>(
+            opaque: *mut c_void,
+        ) -> c_int {
+            // SAFETY: the values are safe according to the contract of
+            // enable_handlers() and qemu_chr_fe_set_handlers()
+            let owner: &T = unsafe { &*(opaque.cast::<T>()) };
+            let r = F::call((owner,));
+            r.try_into().unwrap()
+        }
+
+        unsafe extern "C" fn rust_receive_cb<T, F: for<'a, 'b> FnCall<(&'a T, &'b [u8])>>(
+            opaque: *mut c_void,
+            buf: *const u8,
+            size: c_int,
+        ) {
+            // SAFETY: the values are safe according to the contract of
+            // enable_handlers() and qemu_chr_fe_set_handlers()
+            let owner: &T = unsafe { &*(opaque.cast::<T>()) };
+            let buf = unsafe { slice::from_raw_parts(buf, size.try_into().unwrap()) };
+            F::call((owner, buf))
+        }
+
+        unsafe extern "C" fn rust_event_cb<T, F: for<'a> FnCall<(&'a T, Event)>>(
+            opaque: *mut c_void,
+            event: Event,
+        ) {
+            // SAFETY: the values are safe according to the contract of
+            // enable_handlers() and qemu_chr_fe_set_handlers()
+            let owner: &T = unsafe { &*(opaque.cast::<T>()) };
+            F::call((owner, event))
+        }
+
+        let _: () = CanReceiveFn::ASSERT_IS_SOME;
+        let receive_cb: Option<unsafe extern "C" fn(*mut c_void, *const u8, c_int)> =
+            if ReceiveFn::is_some() {
+                Some(rust_receive_cb::<T, ReceiveFn>)
+            } else {
+                None
+            };
+        let event_cb: Option<unsafe extern "C" fn(*mut c_void, Event)> = if EventFn::is_some() {
+            Some(rust_event_cb::<T, EventFn>)
+        } else {
+            None
+        };
+
+        let mut chr = self.inner.borrow_mut();
+        // SAFETY: the borrow promises that the BQL is taken
+        unsafe {
+            bindings::qemu_chr_fe_set_handlers(
+                addr_of_mut!(*chr),
+                Some(rust_can_receive_cb::<T, CanReceiveFn>),
+                receive_cb,
+                event_cb,
+                None,
+                (owner as *const T as *mut T).cast::<c_void>(),
+                core::ptr::null_mut(),
+                true,
+            );
+        }
+    }
+
+    /// Disable the front-end's character device handlers.
+    pub fn disable_handlers(&self) {
+        let mut chr = self.inner.borrow_mut();
+        // SAFETY: the borrow promises that the BQL is taken
+        unsafe {
+            bindings::qemu_chr_fe_set_handlers(
+                addr_of_mut!(*chr),
+                None,
+                None,
+                None,
+                None,
+                core::ptr::null_mut(),
+                core::ptr::null_mut(),
+                true,
+            );
+        }
+    }
+
+    /// Notify that the frontend is ready to receive data.
+    pub fn accept_input(&self) {
+        let mut chr = self.inner.borrow_mut();
+        // SAFETY: the borrow promises that the BQL is taken
+        unsafe { bindings::qemu_chr_fe_accept_input(addr_of_mut!(*chr)) }
+    }
+
+    /// Temporarily borrow the character device, allowing it to be used
+    /// as an implementor of `Write`.  Note that it is not valid to drop
+    /// the big QEMU lock while the character device is borrowed, as
+    /// that might cause C code to write to the character device.
+    pub fn borrow_mut(&self) -> impl Write + '_ {
+        self.inner.borrow_mut()
+    }
+
+    /// Send a continuous stream of zero bits on the line if `enabled` is
+    /// true, or a short stream if `enabled` is false.
+    pub fn send_break(&self, long: bool) -> io::Result<()> {
+        let mut chr = self.inner.borrow_mut();
+        let mut duration: c_int = long.into();
+        // SAFETY: the borrow promises that the BQL is taken
+        let r = unsafe {
+            bindings::qemu_chr_fe_ioctl(
+                addr_of_mut!(*chr),
+                bindings::CHR_IOCTL_SERIAL_SET_BREAK as i32,
+                addr_of_mut!(duration).cast::<c_void>(),
+            )
+        };
+
+        errno::into_io_result(r).map(|_| ())
+    }
+
+    /// Write data to a character backend from the front end.  This function
+    /// will send data from the front end to the back end.  Unlike
+    /// `write`, this function will block if the back end cannot
+    /// consume all of the data attempted to be written.
+    ///
+    /// Returns the number of bytes consumed (0 if no associated Chardev) or an
+    /// error.
+    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
+        let len = buf.len().try_into().unwrap();
+        // SAFETY: qemu_chr_fe_write is thread-safe
+        let r = unsafe { bindings::qemu_chr_fe_write(self.inner.as_ptr(), buf.as_ptr(), len) };
+        errno::into_io_result(r).map(|cnt| cnt as usize)
+    }
+
+    /// Write data to a character backend from the front end.  This function
+    /// will send data from the front end to the back end.  Unlike
+    /// `write`, this function will block if the back end cannot
+    /// consume all of the data attempted to be written.
+    ///
+    /// Returns the number of bytes consumed (0 if no associated Chardev) or an
+    /// error.
+    pub fn write_all(&self, buf: &[u8]) -> io::Result<()> {
+        let len = buf.len().try_into().unwrap();
+        // SAFETY: qemu_chr_fe_write_all is thread-safe
+        let r = unsafe { bindings::qemu_chr_fe_write_all(self.inner.as_ptr(), buf.as_ptr(), len) };
+        errno::into_io_result(r).and_then(|cnt| {
+            if cnt as usize == buf.len() {
+                Ok(())
+            } else {
+                Err(ErrorKind::WriteZero.into())
+            }
+        })
+    }
+}
 
 unsafe impl ObjectType for Chardev {
     type Class = ChardevClass;
diff --git a/rust/qemu-api/src/irq.rs b/rust/qemu-api/src/irq.rs
index 34c1926..1222d4f 100644
--- a/rust/qemu-api/src/irq.rs
+++ b/rust/qemu-api/src/irq.rs
@@ -8,10 +8,16 @@ use std::{ffi::CStr, marker::PhantomData, os::raw::c_int, ptr};
 
 use crate::{
     bindings::{self, qemu_set_irq},
+    cell::Opaque,
     prelude::*,
     qom::ObjectClass,
 };
 
+/// An opaque wrapper around [`bindings::IRQState`].
+#[repr(transparent)]
+#[derive(Debug, qemu_api_macros::Wrapper)]
+pub struct IRQState(Opaque<bindings::IRQState>);
+
 /// Interrupt sources are used by devices to pass changes to a value (typically
 /// a boolean).  The interrupt sink is usually an interrupt controller or
 /// GPIO controller.
@@ -21,8 +27,7 @@ use crate::{
 /// method sends a `true` value to the sink.  If the guest has to see a
 /// different polarity, that change is performed by the board between the
 /// device and the interrupt controller.
-pub type IRQState = bindings::IRQState;
-
+///
 /// Interrupts are implemented as a pointer to the interrupt "sink", which has
 /// type [`IRQState`].  A device exposes its source as a QOM link property using
 /// a function such as [`SysBusDeviceMethods::init_irq`], and
@@ -40,7 +45,7 @@ pub struct InterruptSource<T = bool>
 where
     c_int: From<T>,
 {
-    cell: BqlCell<*mut IRQState>,
+    cell: BqlCell<*mut bindings::IRQState>,
     _marker: PhantomData<T>,
 }
 
@@ -79,11 +84,11 @@ where
         }
     }
 
-    pub(crate) const fn as_ptr(&self) -> *mut *mut IRQState {
+    pub(crate) const fn as_ptr(&self) -> *mut *mut bindings::IRQState {
         self.cell.as_ptr()
     }
 
-    pub(crate) const fn slice_as_ptr(slice: &[Self]) -> *mut *mut IRQState {
+    pub(crate) const fn slice_as_ptr(slice: &[Self]) -> *mut *mut bindings::IRQState {
         assert!(!slice.is_empty());
         slice[0].as_ptr()
     }
diff --git a/rust/qemu-api/src/memory.rs b/rust/qemu-api/src/memory.rs
index 682951a..fdb1ea1 100644
--- a/rust/qemu-api/src/memory.rs
+++ b/rust/qemu-api/src/memory.rs
@@ -6,9 +6,8 @@
 
 use std::{
     ffi::{CStr, CString},
-    marker::{PhantomData, PhantomPinned},
+    marker::PhantomData,
     os::raw::{c_uint, c_void},
-    ptr::addr_of,
 };
 
 pub use bindings::{hwaddr, MemTxAttrs};
@@ -16,6 +15,7 @@ pub use bindings::{hwaddr, MemTxAttrs};
 use crate::{
     bindings::{self, device_endian, memory_region_init_io},
     callbacks::FnCall,
+    cell::Opaque,
     prelude::*,
     zeroable::Zeroable,
 };
@@ -132,13 +132,13 @@ impl<T> Default for MemoryRegionOpsBuilder<T> {
     }
 }
 
-/// A safe wrapper around [`bindings::MemoryRegion`].  Compared to the
-/// underlying C struct it is marked as pinned because the QOM tree
-/// contains a pointer to it.
-pub struct MemoryRegion {
-    inner: bindings::MemoryRegion,
-    _pin: PhantomPinned,
-}
+/// A safe wrapper around [`bindings::MemoryRegion`].
+#[repr(transparent)]
+#[derive(qemu_api_macros::Wrapper)]
+pub struct MemoryRegion(Opaque<bindings::MemoryRegion>);
+
+unsafe impl Send for MemoryRegion {}
+unsafe impl Sync for MemoryRegion {}
 
 impl MemoryRegion {
     // inline to ensure that it is not included in tests, which only
@@ -157,7 +157,7 @@ impl MemoryRegion {
             let cstr = CString::new(name).unwrap();
             memory_region_init_io(
                 slot,
-                owner.cast::<Object>(),
+                owner.cast::<bindings::Object>(),
                 ops,
                 owner.cast::<c_void>(),
                 cstr.as_ptr(),
@@ -174,13 +174,15 @@ impl MemoryRegion {
         size: u64,
     ) {
         unsafe {
-            Self::do_init_io(&mut self.inner, owner.cast::<Object>(), &ops.0, name, size);
+            Self::do_init_io(
+                self.0.as_mut_ptr(),
+                owner.cast::<Object>(),
+                &ops.0,
+                name,
+                size,
+            );
         }
     }
-
-    pub(crate) const fn as_mut_ptr(&self) -> *mut bindings::MemoryRegion {
-        addr_of!(self.inner) as *mut _
-    }
 }
 
 unsafe impl ObjectType for MemoryRegion {
diff --git a/rust/qemu-api/src/prelude.rs b/rust/qemu-api/src/prelude.rs
index 634acf3..43bfcd5 100644
--- a/rust/qemu-api/src/prelude.rs
+++ b/rust/qemu-api/src/prelude.rs
@@ -17,7 +17,6 @@ pub use crate::qom::InterfaceType;
 pub use crate::qom::IsA;
 pub use crate::qom::Object;
 pub use crate::qom::ObjectCast;
-pub use crate::qom::ObjectCastMut;
 pub use crate::qom::ObjectDeref;
 pub use crate::qom::ObjectClassMethods;
 pub use crate::qom::ObjectMethods;
diff --git a/rust/qemu-api/src/qdev.rs b/rust/qemu-api/src/qdev.rs
index c136457..18b4a9b 100644
--- a/rust/qemu-api/src/qdev.rs
+++ b/rust/qemu-api/src/qdev.rs
@@ -10,12 +10,12 @@ use std::{
     ptr::NonNull,
 };
 
-pub use bindings::{Clock, ClockEvent, DeviceClass, DeviceState, Property, ResetType};
+pub use bindings::{ClockEvent, DeviceClass, Property, ResetType};
 
 use crate::{
     bindings::{self, qdev_init_gpio_in, qdev_init_gpio_out, Error, ResettableClass},
     callbacks::FnCall,
-    cell::bql_locked,
+    cell::{bql_locked, Opaque},
     chardev::Chardev,
     irq::InterruptSource,
     prelude::*,
@@ -23,6 +23,22 @@ use crate::{
     vmstate::VMStateDescription,
 };
 
+/// A safe wrapper around [`bindings::Clock`].
+#[repr(transparent)]
+#[derive(Debug, qemu_api_macros::Wrapper)]
+pub struct Clock(Opaque<bindings::Clock>);
+
+unsafe impl Send for Clock {}
+unsafe impl Sync for Clock {}
+
+/// A safe wrapper around [`bindings::DeviceState`].
+#[repr(transparent)]
+#[derive(Debug, qemu_api_macros::Wrapper)]
+pub struct DeviceState(Opaque<bindings::DeviceState>);
+
+unsafe impl Send for DeviceState {}
+unsafe impl Sync for DeviceState {}
+
 /// Trait providing the contents of the `ResettablePhases` struct,
 /// which is part of the QOM `Resettable` interface.
 pub trait ResettablePhasesImpl {
@@ -52,7 +68,7 @@ pub trait ResettablePhasesImpl {
 /// 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_resettable_enter_fn<T: ResettablePhasesImpl>(
-    obj: *mut Object,
+    obj: *mut bindings::Object,
     typ: ResetType,
 ) {
     let state = NonNull::new(obj).unwrap().cast::<T>();
@@ -65,7 +81,7 @@ unsafe extern "C" fn rust_resettable_enter_fn<T: ResettablePhasesImpl>(
 /// 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_resettable_hold_fn<T: ResettablePhasesImpl>(
-    obj: *mut Object,
+    obj: *mut bindings::Object,
     typ: ResetType,
 ) {
     let state = NonNull::new(obj).unwrap().cast::<T>();
@@ -78,7 +94,7 @@ unsafe extern "C" fn rust_resettable_hold_fn<T: ResettablePhasesImpl>(
 /// 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_resettable_exit_fn<T: ResettablePhasesImpl>(
-    obj: *mut Object,
+    obj: *mut bindings::Object,
     typ: ResetType,
 ) {
     let state = NonNull::new(obj).unwrap().cast::<T>();
@@ -117,7 +133,10 @@ pub trait DeviceImpl: ObjectImpl + ResettablePhasesImpl + IsA<DeviceState> {
 /// 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_realize_fn<T: DeviceImpl>(dev: *mut DeviceState, _errp: *mut *mut Error) {
+unsafe extern "C" fn rust_realize_fn<T: DeviceImpl>(
+    dev: *mut bindings::DeviceState,
+    _errp: *mut *mut Error,
+) {
     let state = NonNull::new(dev).unwrap().cast::<T>();
     T::REALIZE.unwrap()(unsafe { state.as_ref() });
 }
@@ -251,7 +270,7 @@ where
         events: ClockEvent,
     ) -> Owned<Clock> {
         fn do_init_clock_in(
-            dev: *mut DeviceState,
+            dev: &DeviceState,
             name: &str,
             cb: Option<unsafe extern "C" fn(*mut c_void, ClockEvent)>,
             events: ClockEvent,
@@ -265,14 +284,15 @@ where
             unsafe {
                 let cstr = CString::new(name).unwrap();
                 let clk = bindings::qdev_init_clock_in(
-                    dev,
+                    dev.as_mut_ptr(),
                     cstr.as_ptr(),
                     cb,
-                    dev.cast::<c_void>(),
+                    dev.as_void_ptr(),
                     events.0,
                 );
 
-                Owned::from(&*clk)
+                let clk: &Clock = Clock::from_raw(clk);
+                Owned::from(clk)
             }
         }
 
@@ -289,7 +309,7 @@ where
             None
         };
 
-        do_init_clock_in(self.as_mut_ptr(), name, cb, events)
+        do_init_clock_in(self.upcast(), name, cb, events)
     }
 
     /// Add an output clock named `name`.
@@ -304,17 +324,23 @@ where
     fn init_clock_out(&self, name: &str) -> Owned<Clock> {
         unsafe {
             let cstr = CString::new(name).unwrap();
-            let clk = bindings::qdev_init_clock_out(self.as_mut_ptr(), cstr.as_ptr());
+            let clk = bindings::qdev_init_clock_out(self.upcast().as_mut_ptr(), cstr.as_ptr());
 
-            Owned::from(&*clk)
+            let clk: &Clock = Clock::from_raw(clk);
+            Owned::from(clk)
         }
     }
 
     fn prop_set_chr(&self, propname: &str, chr: &Owned<Chardev>) {
         assert!(bql_locked());
         let c_propname = CString::new(propname).unwrap();
+        let chr: &Chardev = chr;
         unsafe {
-            bindings::qdev_prop_set_chr(self.as_mut_ptr(), c_propname.as_ptr(), chr.as_mut_ptr());
+            bindings::qdev_prop_set_chr(
+                self.upcast().as_mut_ptr(),
+                c_propname.as_ptr(),
+                chr.as_mut_ptr(),
+            );
         }
     }
 
@@ -323,8 +349,17 @@ where
         num_lines: u32,
         _cb: F,
     ) {
-        let _: () = F::ASSERT_IS_SOME;
+        fn do_init_gpio_in(
+            dev: &DeviceState,
+            num_lines: u32,
+            gpio_in_cb: unsafe extern "C" fn(*mut c_void, c_int, c_int),
+        ) {
+            unsafe {
+                qdev_init_gpio_in(dev.as_mut_ptr(), Some(gpio_in_cb), num_lines as c_int);
+            }
+        }
 
+        let _: () = F::ASSERT_IS_SOME;
         unsafe extern "C" fn rust_irq_handler<T, F: for<'a> FnCall<(&'a T, u32, u32)>>(
             opaque: *mut c_void,
             line: c_int,
@@ -337,19 +372,13 @@ where
         let gpio_in_cb: unsafe extern "C" fn(*mut c_void, c_int, c_int) =
             rust_irq_handler::<Self::Target, F>;
 
-        unsafe {
-            qdev_init_gpio_in(
-                self.as_mut_ptr::<DeviceState>(),
-                Some(gpio_in_cb),
-                num_lines as c_int,
-            );
-        }
+        do_init_gpio_in(self.upcast(), num_lines, gpio_in_cb);
     }
 
     fn init_gpio_out(&self, pins: &[InterruptSource]) {
         unsafe {
             qdev_init_gpio_out(
-                self.as_mut_ptr::<DeviceState>(),
+                self.upcast().as_mut_ptr(),
                 InterruptSource::slice_as_ptr(pins),
                 pins.len() as c_int,
             );
diff --git a/rust/qemu-api/src/qom.rs b/rust/qemu-api/src/qom.rs
index 5488643..34d7bc0 100644
--- a/rust/qemu-api/src/qom.rs
+++ b/rust/qemu-api/src/qom.rs
@@ -101,16 +101,24 @@ use std::{
     ptr::NonNull,
 };
 
-pub use bindings::{Object, ObjectClass};
+pub use bindings::ObjectClass;
 
 use crate::{
     bindings::{
         self, object_class_dynamic_cast, object_dynamic_cast, object_get_class,
         object_get_typename, object_new, object_ref, object_unref, TypeInfo,
     },
-    cell::bql_locked,
+    cell::{bql_locked, Opaque},
 };
 
+/// A safe wrapper around [`bindings::Object`].
+#[repr(transparent)]
+#[derive(Debug, qemu_api_macros::Wrapper)]
+pub struct Object(Opaque<bindings::Object>);
+
+unsafe impl Send for Object {}
+unsafe impl Sync for Object {}
+
 /// Marker trait: `Self` can be statically upcasted to `P` (i.e. `P` is a direct
 /// or indirect parent of `Self`).
 ///
@@ -199,7 +207,7 @@ impl<T: fmt::Display + ObjectType> fmt::Display for ParentField<T> {
     }
 }
 
-unsafe extern "C" fn rust_instance_init<T: ObjectImpl>(obj: *mut Object) {
+unsafe extern "C" fn rust_instance_init<T: ObjectImpl>(obj: *mut bindings::Object) {
     let mut state = NonNull::new(obj).unwrap().cast::<T>();
     // SAFETY: obj is an instance of T, since rust_instance_init<T>
     // is called from QOM core as the instance_init function
@@ -209,7 +217,7 @@ unsafe extern "C" fn rust_instance_init<T: ObjectImpl>(obj: *mut Object) {
     }
 }
 
-unsafe extern "C" fn rust_instance_post_init<T: ObjectImpl>(obj: *mut Object) {
+unsafe extern "C" fn rust_instance_post_init<T: ObjectImpl>(obj: *mut bindings::Object) {
     let state = NonNull::new(obj).unwrap().cast::<T>();
     // SAFETY: obj is an instance of T, since rust_instance_post_init<T>
     // is called from QOM core as the instance_post_init function
@@ -230,7 +238,7 @@ unsafe extern "C" fn rust_class_init<T: ObjectType + ObjectImpl>(
     <T as ObjectImpl>::CLASS_INIT(unsafe { klass.as_mut() })
 }
 
-unsafe extern "C" fn drop_object<T: ObjectImpl>(obj: *mut Object) {
+unsafe extern "C" fn drop_object<T: ObjectImpl>(obj: *mut bindings::Object) {
     // SAFETY: obj is an instance of T, since drop_object<T> is called
     // from the QOM core function object_deinit() as the instance_finalize
     // function for class T.  Note that while object_deinit() will drop the
@@ -280,14 +288,14 @@ pub unsafe trait ObjectType: Sized {
     /// Return the receiver as an Object.  This is always safe, even
     /// if this type represents an interface.
     fn as_object(&self) -> &Object {
-        unsafe { &*self.as_object_ptr() }
+        unsafe { &*self.as_ptr().cast() }
     }
 
     /// Return the receiver as a const raw pointer to Object.
     /// This is preferrable to `as_object_mut_ptr()` if a C
     /// function only needs a `const Object *`.
-    fn as_object_ptr(&self) -> *const Object {
-        self.as_ptr().cast()
+    fn as_object_ptr(&self) -> *const bindings::Object {
+        self.as_object().as_ptr()
     }
 
     /// Return the receiver as a mutable raw pointer to Object.
@@ -297,8 +305,8 @@ pub unsafe trait ObjectType: Sized {
     /// This cast is always safe, but because the result is mutable
     /// and the incoming reference is not, this should only be used
     /// for calls to C functions, and only if needed.
-    unsafe fn as_object_mut_ptr(&self) -> *mut Object {
-        self.as_object_ptr() as *mut _
+    unsafe fn as_object_mut_ptr(&self) -> *mut bindings::Object {
+        self.as_object().as_mut_ptr()
     }
 }
 
@@ -455,90 +463,7 @@ where
 impl<T: ObjectType> ObjectDeref for &T {}
 impl<T: ObjectType> ObjectCast for &T {}
 
-/// Trait for mutable type casting operations in the QOM hierarchy.
-///
-/// This trait provides the mutable counterparts to [`ObjectCast`]'s conversion
-/// functions. Unlike `ObjectCast`, this trait returns `Result` for fallible
-/// conversions to preserve the original smart pointer if the cast fails. This
-/// is necessary because mutable references cannot be copied, so a failed cast
-/// must return ownership of the original reference. For example:
-///
-/// ```ignore
-/// let mut dev = get_device();
-/// // If this fails, we need the original `dev` back to try something else
-/// match dev.dynamic_cast_mut::<FooDevice>() {
-///    Ok(foodev) => /* use foodev */,
-///    Err(dev) => /* still have ownership of dev */
-/// }
-/// ```
-pub trait ObjectCastMut: Sized + ObjectDeref + DerefMut
-where
-    Self::Target: ObjectType,
-{
-    /// Safely convert from a derived type to one of its parent types.
-    ///
-    /// This is always safe; the [`IsA`] trait provides static verification
-    /// that `Self` dereferences to `U` or a child of `U`.
-    fn upcast_mut<'a, U: ObjectType>(self) -> &'a mut U
-    where
-        Self::Target: IsA<U>,
-        Self: 'a,
-    {
-        // SAFETY: soundness is declared via IsA<U>, which is an unsafe trait
-        unsafe { self.unsafe_cast_mut::<U>() }
-    }
-
-    /// Attempt to convert to a derived type.
-    ///
-    /// Returns `Ok(..)` if the object is of type `U`, or `Err(self)` if the
-    /// object if the conversion failed. This is verified at runtime by
-    /// checking the object's type information.
-    fn downcast_mut<'a, U: IsA<Self::Target>>(self) -> Result<&'a mut U, Self>
-    where
-        Self: 'a,
-    {
-        self.dynamic_cast_mut::<U>()
-    }
-
-    /// Attempt to convert between any two types in the QOM hierarchy.
-    ///
-    /// Returns `Ok(..)` if the object is of type `U`, or `Err(self)` if the
-    /// object if the conversion failed. This is verified at runtime by
-    /// checking the object's type information.
-    fn dynamic_cast_mut<'a, U: ObjectType>(self) -> Result<&'a mut U, Self>
-    where
-        Self: 'a,
-    {
-        unsafe {
-            // SAFETY: upcasting to Object is always valid, and the
-            // return type is either NULL or the argument itself
-            let result: *mut U =
-                object_dynamic_cast(self.as_object_mut_ptr(), U::TYPE_NAME.as_ptr()).cast();
-
-            result.as_mut().ok_or(self)
-        }
-    }
-
-    /// Convert to any QOM type without verification.
-    ///
-    /// # Safety
-    ///
-    /// What safety? You need to know yourself that the cast is correct; only
-    /// use when performance is paramount.  It is still better than a raw
-    /// pointer `cast()`, which does not even check that you remain in the
-    /// realm of QOM `ObjectType`s.
-    ///
-    /// `unsafe_cast::<Object>()` is always safe.
-    unsafe fn unsafe_cast_mut<'a, U: ObjectType>(self) -> &'a mut U
-    where
-        Self: 'a,
-    {
-        unsafe { &mut *self.as_mut_ptr::<Self::Target>().cast::<U>() }
-    }
-}
-
 impl<T: ObjectType> ObjectDeref for &mut T {}
-impl<T: ObjectType> ObjectCastMut for &mut T {}
 
 /// Trait a type must implement to be registered with QEMU.
 pub trait ObjectImpl: ObjectType + IsA<Object> {
@@ -621,7 +546,7 @@ pub trait ObjectImpl: ObjectType + IsA<Object> {
 /// 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_unparent_fn<T: ObjectImpl>(dev: *mut Object) {
+unsafe extern "C" fn rust_unparent_fn<T: ObjectImpl>(dev: *mut bindings::Object) {
     let state = NonNull::new(dev).unwrap().cast::<T>();
     T::UNPARENT.unwrap()(unsafe { state.as_ref() });
 }
@@ -796,8 +721,9 @@ pub trait ObjectClassMethods: IsA<Object> {
         // SAFETY: the object created by object_new is allocated on
         // the heap and has a reference count of 1
         unsafe {
-            let obj = &*object_new(Self::TYPE_NAME.as_ptr());
-            Owned::from_raw(obj.unsafe_cast::<Self>())
+            let raw_obj = object_new(Self::TYPE_NAME.as_ptr());
+            let obj = Object::from_raw(raw_obj).unsafe_cast::<Self>();
+            Owned::from_raw(obj)
         }
     }
 }
diff --git a/rust/qemu-api/src/sysbus.rs b/rust/qemu-api/src/sysbus.rs
index 04821a2..e92502a 100644
--- a/rust/qemu-api/src/sysbus.rs
+++ b/rust/qemu-api/src/sysbus.rs
@@ -6,11 +6,11 @@
 
 use std::{ffi::CStr, ptr::addr_of_mut};
 
-pub use bindings::{SysBusDevice, SysBusDeviceClass};
+pub use bindings::SysBusDeviceClass;
 
 use crate::{
     bindings,
-    cell::bql_locked,
+    cell::{bql_locked, Opaque},
     irq::{IRQState, InterruptSource},
     memory::MemoryRegion,
     prelude::*,
@@ -18,6 +18,14 @@ use crate::{
     qom::Owned,
 };
 
+/// A safe wrapper around [`bindings::SysBusDevice`].
+#[repr(transparent)]
+#[derive(Debug, qemu_api_macros::Wrapper)]
+pub struct SysBusDevice(Opaque<bindings::SysBusDevice>);
+
+unsafe impl Send for SysBusDevice {}
+unsafe impl Sync for SysBusDevice {}
+
 unsafe impl ObjectType for SysBusDevice {
     type Class = SysBusDeviceClass;
     const TYPE_NAME: &'static CStr =
@@ -49,7 +57,7 @@ where
     fn init_mmio(&self, iomem: &MemoryRegion) {
         assert!(bql_locked());
         unsafe {
-            bindings::sysbus_init_mmio(self.as_mut_ptr(), iomem.as_mut_ptr());
+            bindings::sysbus_init_mmio(self.upcast().as_mut_ptr(), iomem.as_mut_ptr());
         }
     }
 
@@ -60,7 +68,21 @@ where
     fn init_irq(&self, irq: &InterruptSource) {
         assert!(bql_locked());
         unsafe {
-            bindings::sysbus_init_irq(self.as_mut_ptr(), irq.as_ptr());
+            bindings::sysbus_init_irq(self.upcast().as_mut_ptr(), irq.as_ptr());
+        }
+    }
+
+    // TODO: do we want a type like GuestAddress here?
+    fn mmio_addr(&self, id: u32) -> Option<u64> {
+        assert!(bql_locked());
+        // SAFETY: the BQL ensures that no one else writes to sbd.mmio[], and
+        // the SysBusDevice must be initialized to get an IsA<SysBusDevice>.
+        let sbd = unsafe { *self.upcast().as_ptr() };
+        let id: usize = id.try_into().unwrap();
+        if sbd.mmio[id].memory.is_null() {
+            None
+        } else {
+            Some(sbd.mmio[id].addr)
         }
     }
 
@@ -69,7 +91,7 @@ where
         assert!(bql_locked());
         let id: i32 = id.try_into().unwrap();
         unsafe {
-            bindings::sysbus_mmio_map(self.as_mut_ptr(), id, addr);
+            bindings::sysbus_mmio_map(self.upcast().as_mut_ptr(), id, addr);
         }
     }
 
@@ -79,8 +101,9 @@ where
     fn connect_irq(&self, id: u32, irq: &Owned<IRQState>) {
         assert!(bql_locked());
         let id: i32 = id.try_into().unwrap();
+        let irq: &IRQState = irq;
         unsafe {
-            bindings::sysbus_connect_irq(self.as_mut_ptr(), id, irq.as_mut_ptr());
+            bindings::sysbus_connect_irq(self.upcast().as_mut_ptr(), id, irq.as_mut_ptr());
         }
     }
 
@@ -88,7 +111,10 @@ where
         // TODO: return an Error
         assert!(bql_locked());
         unsafe {
-            bindings::sysbus_realize(self.as_mut_ptr(), addr_of_mut!(bindings::error_fatal));
+            bindings::sysbus_realize(
+                self.upcast().as_mut_ptr(),
+                addr_of_mut!(bindings::error_fatal),
+            );
         }
     }
 }
diff --git a/rust/qemu-api/src/timer.rs b/rust/qemu-api/src/timer.rs
index a593538..f0b04ef 100644
--- a/rust/qemu-api/src/timer.rs
+++ b/rust/qemu-api/src/timer.rs
@@ -2,31 +2,51 @@
 // Author(s): Zhao Liu <zhai1.liu@intel.com>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-use std::os::raw::{c_int, c_void};
+use std::{
+    os::raw::{c_int, c_void},
+    pin::Pin,
+};
 
 use crate::{
     bindings::{self, qemu_clock_get_ns, timer_del, timer_init_full, timer_mod, QEMUClockType},
     callbacks::FnCall,
+    cell::Opaque,
 };
 
-pub type Timer = bindings::QEMUTimer;
-pub type TimerListGroup = bindings::QEMUTimerListGroup;
+/// A safe wrapper around [`bindings::QEMUTimer`].
+#[repr(transparent)]
+#[derive(Debug, qemu_api_macros::Wrapper)]
+pub struct Timer(Opaque<bindings::QEMUTimer>);
+
+unsafe impl Send for Timer {}
+unsafe impl Sync for Timer {}
+
+#[repr(transparent)]
+#[derive(qemu_api_macros::Wrapper)]
+pub struct TimerListGroup(Opaque<bindings::QEMUTimerListGroup>);
+
+unsafe impl Send for TimerListGroup {}
+unsafe impl Sync for TimerListGroup {}
 
 impl Timer {
     pub const MS: u32 = bindings::SCALE_MS;
     pub const US: u32 = bindings::SCALE_US;
     pub const NS: u32 = bindings::SCALE_NS;
 
-    pub fn new() -> Self {
-        Default::default()
-    }
-
-    const fn as_mut_ptr(&self) -> *mut Self {
-        self as *const Timer as *mut _
+    /// Create a `Timer` struct without initializing it.
+    ///
+    /// # Safety
+    ///
+    /// The timer must be initialized before it is armed with
+    /// [`modify`](Self::modify).
+    pub unsafe fn new() -> Self {
+        // SAFETY: requirements relayed to callers of Timer::new
+        Self(unsafe { Opaque::zeroed() })
     }
 
+    /// Create a new timer with the given attributes.
     pub fn init_full<'timer, 'opaque: 'timer, T, F>(
-        &'timer mut self,
+        self: Pin<&'timer mut Self>,
         timer_list_group: Option<&TimerListGroup>,
         clk_type: ClockType,
         scale: u32,
@@ -51,7 +71,7 @@ impl Timer {
         // SAFETY: the opaque outlives the timer
         unsafe {
             timer_init_full(
-                self,
+                self.as_mut_ptr(),
                 if let Some(g) = timer_list_group {
                     g as *const TimerListGroup as *mut _
                 } else {
@@ -67,14 +87,19 @@ impl Timer {
     }
 
     pub fn modify(&self, expire_time: u64) {
+        // SAFETY: the only way to obtain a Timer safely is via methods that
+        // take a Pin<&mut Self>, therefore the timer is pinned
         unsafe { timer_mod(self.as_mut_ptr(), expire_time as i64) }
     }
 
     pub fn delete(&self) {
+        // SAFETY: the only way to obtain a Timer safely is via methods that
+        // take a Pin<&mut Self>, therefore the timer is pinned
         unsafe { timer_del(self.as_mut_ptr()) }
     }
 }
 
+// FIXME: use something like PinnedDrop from the pinned_init crate
 impl Drop for Timer {
     fn drop(&mut self) {
         self.delete()
diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs
index 24a4dc8..f0510ae 100644
--- a/rust/qemu-api/src/vmstate.rs
+++ b/rust/qemu-api/src/vmstate.rs
@@ -330,6 +330,7 @@ macro_rules! impl_vmstate_transparent {
 
 impl_vmstate_transparent!(std::cell::Cell<T> where T: VMState);
 impl_vmstate_transparent!(std::cell::UnsafeCell<T> where T: VMState);
+impl_vmstate_transparent!(std::pin::Pin<T> where T: VMState);
 impl_vmstate_transparent!(crate::cell::BqlCell<T> where T: VMState);
 impl_vmstate_transparent!(crate::cell::BqlRefCell<T> where T: VMState);
 
@@ -469,7 +470,7 @@ macro_rules! vmstate_clock {
                 $crate::assert_field_type!(
                     $struct_name,
                     $field_name,
-                    $crate::qom::Owned<$crate::bindings::Clock>
+                    $crate::qom::Owned<$crate::qdev::Clock>
                 );
                 $crate::offset_of!($struct_name, $field_name)
             },
diff --git a/rust/qemu-api/src/zeroable.rs b/rust/qemu-api/src/zeroable.rs
index 47b6977..a3415a2 100644
--- a/rust/qemu-api/src/zeroable.rs
+++ b/rust/qemu-api/src/zeroable.rs
@@ -106,3 +106,4 @@ impl_zeroable!(crate::bindings::MemoryRegionOps__bindgen_ty_1);
 impl_zeroable!(crate::bindings::MemoryRegionOps__bindgen_ty_2);
 impl_zeroable!(crate::bindings::MemoryRegionOps);
 impl_zeroable!(crate::bindings::MemTxAttrs);
+impl_zeroable!(crate::bindings::CharBackend);
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index e398578..269122e 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -2,13 +2,10 @@
 // Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-use std::{
-    ffi::{c_void, CStr},
-    ptr::{addr_of, addr_of_mut},
-};
+use std::{ffi::CStr, ptr::addr_of};
 
 use qemu_api::{
-    bindings::{module_call_init, module_init_type, object_new, object_unref, qdev_prop_bool},
+    bindings::{module_call_init, module_init_type, qdev_prop_bool},
     c_str,
     cell::{self, BqlCell},
     declare_properties, define_property,
@@ -182,30 +179,3 @@ fn test_cast() {
         assert_eq!(addr_of!(*sbd_ref), p_ptr.cast());
     }
 }
-
-#[test]
-#[allow(clippy::shadow_unrelated)]
-/// Test casts on mutable references.
-fn test_cast_mut() {
-    init_qom();
-    let p: *mut DummyState = unsafe { object_new(DummyState::TYPE_NAME.as_ptr()).cast() };
-
-    let p_ref: &mut DummyState = unsafe { &mut *p };
-    let obj_ref: &mut Object = p_ref.upcast_mut();
-    assert_eq!(addr_of_mut!(*obj_ref), p.cast());
-
-    let sbd_ref: Result<&mut SysBusDevice, &mut Object> = obj_ref.dynamic_cast_mut();
-    let obj_ref = sbd_ref.unwrap_err();
-
-    let dev_ref: Result<&mut DeviceState, &mut Object> = obj_ref.downcast_mut();
-    let dev_ref = dev_ref.unwrap();
-    assert_eq!(addr_of_mut!(*dev_ref), p.cast());
-
-    // SAFETY: the cast is wrong, but the value is only used for comparison
-    unsafe {
-        let sbd_ref: &mut SysBusDevice = obj_ref.unsafe_cast_mut();
-        assert_eq!(addr_of_mut!(*sbd_ref), p.cast());
-
-        object_unref(p_ref.as_object_mut_ptr().cast::<c_void>());
-    }
-}