From 7a35e2fb80df4c536cc808e498a259d96d0a804e Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Tue, 5 Nov 2024 18:03:12 +0100
Subject: rust: fix a couple style issues from clippy

These are reported as clippy::semicolon_inside_block and clippy::as_ptr_cast_mut.

clippy::semicolon_inside_block can be configured not to lint single-line
blocks; just go with the default.

Reviewed-by: Junjie Mao <junjie.mao@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/qemu-api/tests/tests.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'rust/qemu-api/tests/tests.rs')

diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index 43a4827de1..925f5a3c77 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -74,6 +74,6 @@ fn test_device_decl_macros() {
 
     unsafe {
         module_call_init(module_init_type::MODULE_INIT_QOM);
-        object_unref(object_new(DummyState::TYPE_NAME.as_ptr()) as *mut _);
+        object_unref(object_new(DummyState::TYPE_NAME.as_ptr()).cast());
     }
 }
-- 
cgit 1.4.1


From b2a4854508a02fc8a585890e0272c8ae5fbad5c1 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 28 Oct 2024 11:28:23 +0100
Subject: rust: qom: add default definitions for ObjectImpl

Remove a bunch of duplicate const definitions.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/char/pl011/src/device.rs | 6 ------
 rust/qemu-api/src/definitions.rs | 8 ++++----
 rust/qemu-api/tests/tests.rs     | 4 ----
 3 files changed, 4 insertions(+), 14 deletions(-)

(limited to 'rust/qemu-api/tests/tests.rs')

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index c5c8c463d3..3d173ae816 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -109,10 +109,7 @@ impl ObjectImpl for PL011State {
     const TYPE_INFO: qemu_api::bindings::TypeInfo = qemu_api::type_info! { Self };
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011;
     const PARENT_TYPE_NAME: Option<&'static CStr> = Some(TYPE_SYS_BUS_DEVICE);
-    const ABSTRACT: bool = false;
     const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = Some(pl011_init);
-    const INSTANCE_POST_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
-    const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
 }
 
 #[repr(C)]
@@ -666,8 +663,5 @@ impl ObjectImpl for PL011Luminary {
     const TYPE_INFO: qemu_api::bindings::TypeInfo = qemu_api::type_info! { Self };
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011_LUMINARY;
     const PARENT_TYPE_NAME: Option<&'static CStr> = Some(crate::TYPE_PL011);
-    const ABSTRACT: bool = false;
     const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = Some(pl011_luminary_init);
-    const INSTANCE_POST_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
-    const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
 }
diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
index 26597934bb..92b3c6f911 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -14,10 +14,10 @@ pub trait ObjectImpl {
     const TYPE_INFO: TypeInfo;
     const TYPE_NAME: &'static CStr;
     const PARENT_TYPE_NAME: Option<&'static CStr>;
-    const ABSTRACT: bool;
-    const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)>;
-    const INSTANCE_POST_INIT: Option<unsafe extern "C" fn(obj: *mut Object)>;
-    const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)>;
+    const ABSTRACT: bool = false;
+    const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
+    const INSTANCE_POST_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
+    const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
 }
 
 pub trait Class {
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index 925f5a3c77..f793ff26e5 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -58,10 +58,6 @@ fn test_device_decl_macros() {
         const TYPE_INFO: qemu_api::bindings::TypeInfo = qemu_api::type_info! { Self };
         const TYPE_NAME: &'static CStr = c_str!("dummy");
         const PARENT_TYPE_NAME: Option<&'static CStr> = Some(device_class::TYPE_DEVICE);
-        const ABSTRACT: bool = false;
-        const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
-        const INSTANCE_POST_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
-        const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
     }
 
     impl Class for DummyClass {
-- 
cgit 1.4.1


From 93ea0896eaa97adfcc664fa65b5b70e555a652ff Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 28 Oct 2024 13:05:43 +0100
Subject: rust: qom: rename Class trait to ClassInitImpl

While at it, document it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/char/pl011/src/device.rs |  4 ++--
 rust/qemu-api/src/definitions.rs | 25 ++++++++++++++++++++++---
 rust/qemu-api/tests/tests.rs     |  4 ++--
 3 files changed, 26 insertions(+), 7 deletions(-)

(limited to 'rust/qemu-api/tests/tests.rs')

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index 3d173ae816..bd12067aaf 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -117,7 +117,7 @@ pub struct PL011Class {
     _inner: [u8; 0],
 }
 
-impl qemu_api::definitions::Class for PL011Class {
+impl qemu_api::definitions::ClassInitImpl for PL011Class {
     const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
         Some(crate::device_class::pl011_class_init);
     const CLASS_BASE_INIT: Option<
@@ -650,7 +650,7 @@ pub unsafe extern "C" fn pl011_luminary_init(obj: *mut Object) {
     }
 }
 
-impl qemu_api::definitions::Class for PL011LuminaryClass {
+impl qemu_api::definitions::ClassInitImpl for PL011LuminaryClass {
     const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
         None;
     const CLASS_BASE_INIT: Option<
diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
index 92b3c6f911..3291f4242c 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -20,8 +20,27 @@ pub trait ObjectImpl {
     const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
 }
 
-pub trait Class {
+/// Trait used to fill in a class struct.
+///
+/// Each QOM class that has virtual methods describes them in a
+/// _class struct_.  Class structs include a parent field corresponding
+/// to the vtable of the parent class, all the way up to [`ObjectClass`].
+/// Each QOM type has one such class struct.
+///
+/// The Rust implementation of methods will usually come from a trait
+/// like [`ObjectImpl`].
+pub trait ClassInitImpl {
+    /// Function that is called after all parent class initialization
+    /// has occurred.  On entry, the virtual method pointers are set to
+    /// the default values coming from the parent classes; the function
+    /// can change them to override virtual methods of a parent class.
     const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)>;
+
+    /// Called on descendent classes after all parent class initialization
+    /// has occurred, but before the class itself is initialized.  This
+    /// is only useful if a class is not a leaf, and can be used to undo
+    /// the effects of copying the contents of the parent's class struct
+    /// to the descendants.
     const CLASS_BASE_INIT: Option<
         unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void),
     >;
@@ -82,8 +101,8 @@ macro_rules! type_info {
             instance_finalize: <$t as $crate::definitions::ObjectImpl>::INSTANCE_FINALIZE,
             abstract_: <$t as $crate::definitions::ObjectImpl>::ABSTRACT,
             class_size:  ::core::mem::size_of::<<$t as $crate::definitions::ObjectImpl>::Class>(),
-            class_init: <<$t as $crate::definitions::ObjectImpl>::Class as $crate::definitions::Class>::CLASS_INIT,
-            class_base_init: <<$t as $crate::definitions::ObjectImpl>::Class as $crate::definitions::Class>::CLASS_BASE_INIT,
+            class_init: <<$t as $crate::definitions::ObjectImpl>::Class as $crate::definitions::ClassInitImpl>::CLASS_INIT,
+            class_base_init: <<$t as $crate::definitions::ObjectImpl>::Class as $crate::definitions::ClassInitImpl>::CLASS_BASE_INIT,
             class_data: ::core::ptr::null_mut(),
             interfaces: ::core::ptr::null_mut(),
         };
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index f793ff26e5..704c63c846 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -7,7 +7,7 @@ use std::{ffi::CStr, os::raw::c_void};
 use qemu_api::{
     bindings::*,
     c_str, declare_properties, define_property,
-    definitions::{Class, ObjectImpl},
+    definitions::{ClassInitImpl, ObjectImpl},
     device_class, device_class_init,
     zeroable::Zeroable,
 };
@@ -60,7 +60,7 @@ fn test_device_decl_macros() {
         const PARENT_TYPE_NAME: Option<&'static CStr> = Some(device_class::TYPE_DEVICE);
     }
 
-    impl Class for DummyClass {
+    impl ClassInitImpl for DummyClass {
         const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
             Some(dummy_class_init);
         const CLASS_BASE_INIT: Option<
-- 
cgit 1.4.1


From 3701fb22dfd438993e76e158beb97683359d1dd9 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 28 Oct 2024 11:47:12 +0100
Subject: rust: qom: convert type_info! macro to an associated const

type_info! is only used in the definition of ObjectImpl::TYPE_INFO, and
in fact in all of them.  Pull type_info!'s definition into the ObjectImpl
trait, thus simplifying the external interface of qemu_api::definitions.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/char/pl011/src/device.rs |  6 ++---
 rust/qemu-api/src/definitions.rs | 50 ++++++++++++++++++----------------------
 rust/qemu-api/tests/tests.rs     |  1 -
 3 files changed, 24 insertions(+), 33 deletions(-)

(limited to 'rust/qemu-api/tests/tests.rs')

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index bd12067aaf..bcb146c24d 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -106,7 +106,6 @@ pub struct PL011State {
 
 impl ObjectImpl for PL011State {
     type Class = PL011Class;
-    const TYPE_INFO: qemu_api::bindings::TypeInfo = qemu_api::type_info! { Self };
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011;
     const PARENT_TYPE_NAME: Option<&'static CStr> = Some(TYPE_SYS_BUS_DEVICE);
     const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = Some(pl011_init);
@@ -149,7 +148,7 @@ impl PL011State {
                 addr_of_mut!(*self).cast::<Object>(),
                 &PL011_OPS,
                 addr_of_mut!(*self).cast::<c_void>(),
-                Self::TYPE_INFO.name,
+                Self::TYPE_NAME.as_ptr(),
                 0x1000,
             );
             sysbus_init_mmio(sbd, addr_of_mut!(self.iomem));
@@ -598,7 +597,7 @@ pub unsafe extern "C" fn pl011_create(
     chr: *mut Chardev,
 ) -> *mut DeviceState {
     unsafe {
-        let dev: *mut DeviceState = qdev_new(PL011State::TYPE_INFO.name);
+        let dev: *mut DeviceState = qdev_new(PL011State::TYPE_NAME.as_ptr());
         let sysbus: *mut SysBusDevice = dev.cast::<SysBusDevice>();
 
         qdev_prop_set_chr(dev, c_str!("chardev").as_ptr(), chr);
@@ -660,7 +659,6 @@ impl qemu_api::definitions::ClassInitImpl for PL011LuminaryClass {
 
 impl ObjectImpl for PL011Luminary {
     type Class = PL011LuminaryClass;
-    const TYPE_INFO: qemu_api::bindings::TypeInfo = qemu_api::type_info! { Self };
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011_LUMINARY;
     const PARENT_TYPE_NAME: Option<&'static CStr> = Some(crate::TYPE_PL011);
     const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = Some(pl011_luminary_init);
diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
index 3291f4242c..6ecfaf51b0 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -9,15 +9,34 @@ use std::{ffi::CStr, os::raw::c_void};
 use crate::bindings::{Object, ObjectClass, TypeInfo};
 
 /// Trait a type must implement to be registered with QEMU.
-pub trait ObjectImpl {
-    type Class;
-    const TYPE_INFO: TypeInfo;
+pub trait ObjectImpl: Sized {
+    type Class: ClassInitImpl;
     const TYPE_NAME: &'static CStr;
     const PARENT_TYPE_NAME: Option<&'static CStr>;
     const ABSTRACT: bool = false;
     const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
     const INSTANCE_POST_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
     const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
+
+    const TYPE_INFO: TypeInfo = TypeInfo {
+        name: Self::TYPE_NAME.as_ptr(),
+        parent: if let Some(pname) = Self::PARENT_TYPE_NAME {
+            pname.as_ptr()
+        } else {
+            core::ptr::null_mut()
+        },
+        instance_size: core::mem::size_of::<Self>(),
+        instance_align: core::mem::align_of::<Self>(),
+        instance_init: Self::INSTANCE_INIT,
+        instance_post_init: Self::INSTANCE_POST_INIT,
+        instance_finalize: Self::INSTANCE_FINALIZE,
+        abstract_: Self::ABSTRACT,
+        class_size: core::mem::size_of::<Self::Class>(),
+        class_init: <Self::Class as ClassInitImpl>::CLASS_INIT,
+        class_base_init: <Self::Class as ClassInitImpl>::CLASS_BASE_INIT,
+        class_data: core::ptr::null_mut(),
+        interfaces: core::ptr::null_mut(),
+    };
 }
 
 /// Trait used to fill in a class struct.
@@ -83,28 +102,3 @@ macro_rules! module_init {
         }
     };
 }
-
-#[macro_export]
-macro_rules! type_info {
-    ($t:ty) => {
-        $crate::bindings::TypeInfo {
-            name: <$t as $crate::definitions::ObjectImpl>::TYPE_NAME.as_ptr(),
-            parent: if let Some(pname) = <$t as $crate::definitions::ObjectImpl>::PARENT_TYPE_NAME {
-                pname.as_ptr()
-            } else {
-                ::core::ptr::null_mut()
-            },
-            instance_size: ::core::mem::size_of::<$t>(),
-            instance_align: ::core::mem::align_of::<$t>(),
-            instance_init: <$t as $crate::definitions::ObjectImpl>::INSTANCE_INIT,
-            instance_post_init: <$t as $crate::definitions::ObjectImpl>::INSTANCE_POST_INIT,
-            instance_finalize: <$t as $crate::definitions::ObjectImpl>::INSTANCE_FINALIZE,
-            abstract_: <$t as $crate::definitions::ObjectImpl>::ABSTRACT,
-            class_size:  ::core::mem::size_of::<<$t as $crate::definitions::ObjectImpl>::Class>(),
-            class_init: <<$t as $crate::definitions::ObjectImpl>::Class as $crate::definitions::ClassInitImpl>::CLASS_INIT,
-            class_base_init: <<$t as $crate::definitions::ObjectImpl>::Class as $crate::definitions::ClassInitImpl>::CLASS_BASE_INIT,
-            class_data: ::core::ptr::null_mut(),
-            interfaces: ::core::ptr::null_mut(),
-        };
-    }
-}
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index 704c63c846..7f9df348b0 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -55,7 +55,6 @@ fn test_device_decl_macros() {
 
     impl ObjectImpl for DummyState {
         type Class = DummyClass;
-        const TYPE_INFO: qemu_api::bindings::TypeInfo = qemu_api::type_info! { Self };
         const TYPE_NAME: &'static CStr = c_str!("dummy");
         const PARENT_TYPE_NAME: Option<&'static CStr> = Some(device_class::TYPE_DEVICE);
     }
-- 
cgit 1.4.1


From c6c4f3e0d90990c642523c087482eac3f42566c1 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 28 Oct 2024 14:42:23 +0100
Subject: rust: qom: move ClassInitImpl to the instance side

Put all traits on the instance struct, which makes it possible to reuse
class structs if no new virtual methods or class fields are added.
This is almost always the case for devices (because they are leaf
classes), which is the primary use case for Rust.

This is also simpler: soon we will find the implemented methods without
macros, and this removes the need to go from the class struct to the
instance struct to find the implementation of the *Impl traits.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/char/pl011/src/device.rs | 4 ++--
 rust/qemu-api/src/definitions.rs | 8 ++++----
 rust/qemu-api/tests/tests.rs     | 2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

(limited to 'rust/qemu-api/tests/tests.rs')

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index bcb146c24d..2384d4bcb9 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -116,7 +116,7 @@ pub struct PL011Class {
     _inner: [u8; 0],
 }
 
-impl qemu_api::definitions::ClassInitImpl for PL011Class {
+impl qemu_api::definitions::ClassInitImpl for PL011State {
     const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
         Some(crate::device_class::pl011_class_init);
     const CLASS_BASE_INIT: Option<
@@ -649,7 +649,7 @@ pub unsafe extern "C" fn pl011_luminary_init(obj: *mut Object) {
     }
 }
 
-impl qemu_api::definitions::ClassInitImpl for PL011LuminaryClass {
+impl qemu_api::definitions::ClassInitImpl for PL011Luminary {
     const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
         None;
     const CLASS_BASE_INIT: Option<
diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
index 6ecfaf51b0..487712611f 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -9,8 +9,8 @@ use std::{ffi::CStr, os::raw::c_void};
 use crate::bindings::{Object, ObjectClass, TypeInfo};
 
 /// Trait a type must implement to be registered with QEMU.
-pub trait ObjectImpl: Sized {
-    type Class: ClassInitImpl;
+pub trait ObjectImpl: ClassInitImpl + Sized {
+    type Class;
     const TYPE_NAME: &'static CStr;
     const PARENT_TYPE_NAME: Option<&'static CStr>;
     const ABSTRACT: bool = false;
@@ -32,8 +32,8 @@ pub trait ObjectImpl: Sized {
         instance_finalize: Self::INSTANCE_FINALIZE,
         abstract_: Self::ABSTRACT,
         class_size: core::mem::size_of::<Self::Class>(),
-        class_init: <Self::Class as ClassInitImpl>::CLASS_INIT,
-        class_base_init: <Self::Class as ClassInitImpl>::CLASS_BASE_INIT,
+        class_init: <Self as ClassInitImpl>::CLASS_INIT,
+        class_base_init: <Self as ClassInitImpl>::CLASS_BASE_INIT,
         class_data: core::ptr::null_mut(),
         interfaces: core::ptr::null_mut(),
     };
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index 7f9df348b0..fd0c979121 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -59,7 +59,7 @@ fn test_device_decl_macros() {
         const PARENT_TYPE_NAME: Option<&'static CStr> = Some(device_class::TYPE_DEVICE);
     }
 
-    impl ClassInitImpl for DummyClass {
+    impl ClassInitImpl for DummyState {
         const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
             Some(dummy_class_init);
         const CLASS_BASE_INIT: Option<
-- 
cgit 1.4.1


From 8c80c472da6342c5924bc4ea7e87c77ca61477b8 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 28 Oct 2024 10:29:27 +0100
Subject: rust: qdev: move device_class_init! body to generic function,
 ClassInitImpl implementation to macro

Use a trait to access the former parameters to device_class_init!.
This allows hiding the details of the class_init implementation behind
a generic function and makes higher-level functionality available from
qemu_api.

The implementation of ClassInitImpl is then the same for all devices and
is easily macroized.  Later on, we can remove the need to implement
ClassInitImpl by hand for all device types, and stop making
rust_device_class_init<>() public.

While at it, document the members of DeviceImpl.

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/char/pl011/src/device.rs       | 34 +++++++------
 rust/hw/char/pl011/src/device_class.rs |  8 ----
 rust/qemu-api/src/device_class.rs      | 87 +++++++++++++++++++++++++++-------
 rust/qemu-api/tests/tests.rs           | 30 +++++-------
 4 files changed, 103 insertions(+), 56 deletions(-)

(limited to 'rust/qemu-api/tests/tests.rs')

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index 2384d4bcb9..28b1924337 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -12,11 +12,13 @@ use qemu_api::{
     bindings::{self, *},
     c_str,
     definitions::ObjectImpl,
-    device_class::TYPE_SYS_BUS_DEVICE,
+    device_class::{DeviceImpl, TYPE_SYS_BUS_DEVICE},
+    impl_device_class,
     irq::InterruptSource,
 };
 
 use crate::{
+    device_class,
     memory_ops::PL011_OPS,
     registers::{self, Interrupt},
     RegisterOffset,
@@ -116,14 +118,20 @@ pub struct PL011Class {
     _inner: [u8; 0],
 }
 
-impl qemu_api::definitions::ClassInitImpl for PL011State {
-    const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
-        Some(crate::device_class::pl011_class_init);
-    const CLASS_BASE_INIT: Option<
-        unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void),
-    > = None;
+impl DeviceImpl for PL011State {
+    fn properties() -> &'static [Property] {
+        &device_class::PL011_PROPERTIES
+    }
+    fn vmsd() -> Option<&'static VMStateDescription> {
+        Some(&device_class::VMSTATE_PL011)
+    }
+    const REALIZE: Option<unsafe extern "C" fn(*mut DeviceState, *mut *mut Error)> =
+        Some(device_class::pl011_realize);
+    const RESET: Option<unsafe extern "C" fn(*mut DeviceState)> = Some(device_class::pl011_reset);
 }
 
+impl_device_class!(PL011State);
+
 impl PL011State {
     /// Initializes a pre-allocated, unitialized instance of `PL011State`.
     ///
@@ -649,17 +657,13 @@ pub unsafe extern "C" fn pl011_luminary_init(obj: *mut Object) {
     }
 }
 
-impl qemu_api::definitions::ClassInitImpl for PL011Luminary {
-    const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
-        None;
-    const CLASS_BASE_INIT: Option<
-        unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void),
-    > = None;
-}
-
 impl ObjectImpl for PL011Luminary {
     type Class = PL011LuminaryClass;
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011_LUMINARY;
     const PARENT_TYPE_NAME: Option<&'static CStr> = Some(crate::TYPE_PL011);
     const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = Some(pl011_luminary_init);
 }
+
+impl DeviceImpl for PL011Luminary {}
+
+impl_device_class!(PL011Luminary);
diff --git a/rust/hw/char/pl011/src/device_class.rs b/rust/hw/char/pl011/src/device_class.rs
index a707fde138..c61b6bb025 100644
--- a/rust/hw/char/pl011/src/device_class.rs
+++ b/rust/hw/char/pl011/src/device_class.rs
@@ -93,14 +93,6 @@ qemu_api::declare_properties! {
     ),
 }
 
-qemu_api::device_class_init! {
-    pl011_class_init,
-    props => PL011_PROPERTIES,
-    realize_fn => Some(pl011_realize),
-    legacy_reset_fn => Some(pl011_reset),
-    vmsd => VMSTATE_PL011,
-}
-
 /// # Safety
 ///
 /// We expect the FFI user of this function to pass a valid pointer, that has
diff --git a/rust/qemu-api/src/device_class.rs b/rust/qemu-api/src/device_class.rs
index 922bbce1bb..f683f94f2a 100644
--- a/rust/qemu-api/src/device_class.rs
+++ b/rust/qemu-api/src/device_class.rs
@@ -2,25 +2,80 @@
 // Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-use std::ffi::CStr;
+use std::{ffi::CStr, os::raw::c_void};
 
-use crate::bindings;
+use crate::{
+    bindings::{self, DeviceClass, DeviceState, Error, ObjectClass, Property, VMStateDescription},
+    zeroable::Zeroable,
+};
+
+/// Trait providing the contents of [`DeviceClass`].
+pub trait DeviceImpl {
+    /// _Realization_ is the second stage of device creation. It contains
+    /// all operations that depend on device properties and can fail (note:
+    /// this is not yet supported for Rust devices).
+    ///
+    /// If not `None`, the parent class's `realize` method is overridden
+    /// with the function pointed to by `REALIZE`.
+    const REALIZE: Option<unsafe extern "C" fn(*mut DeviceState, *mut *mut Error)> = None;
+
+    /// If not `None`, the parent class's `reset` method is overridden
+    /// with the function pointed to by `RESET`.
+    ///
+    /// Rust does not yet support the three-phase reset protocol; this is
+    /// usually okay for leaf classes.
+    const RESET: Option<unsafe extern "C" fn(dev: *mut DeviceState)> = None;
+
+    /// An array providing the properties that the user can set on the
+    /// device.  Not a `const` because referencing statics in constants
+    /// is unstable until Rust 1.83.0.
+    fn properties() -> &'static [Property] {
+        &[Zeroable::ZERO; 1]
+    }
+
+    /// A `VMStateDescription` providing the migration format for the device
+    /// Not a `const` because referencing statics in constants is unstable
+    /// until Rust 1.83.0.
+    fn vmsd() -> Option<&'static VMStateDescription> {
+        None
+    }
+}
+
+/// # Safety
+///
+/// We expect the FFI user of this function to pass a valid pointer that
+/// can be downcasted to type `DeviceClass`, because `T` implements
+/// `DeviceImpl`.
+pub unsafe extern "C" fn rust_device_class_init<T: DeviceImpl>(
+    klass: *mut ObjectClass,
+    _: *mut c_void,
+) {
+    let mut dc = ::core::ptr::NonNull::new(klass.cast::<DeviceClass>()).unwrap();
+    unsafe {
+        let dc = dc.as_mut();
+        if let Some(realize_fn) = <T as DeviceImpl>::REALIZE {
+            dc.realize = Some(realize_fn);
+        }
+        if let Some(reset_fn) = <T as DeviceImpl>::RESET {
+            bindings::device_class_set_legacy_reset(dc, Some(reset_fn));
+        }
+        if let Some(vmsd) = <T as DeviceImpl>::vmsd() {
+            dc.vmsd = vmsd;
+        }
+        bindings::device_class_set_props(dc, <T as DeviceImpl>::properties().as_ptr());
+    }
+}
 
 #[macro_export]
-macro_rules! device_class_init {
-    ($func:ident, props => $props:ident, realize_fn => $realize_fn:expr, legacy_reset_fn => $legacy_reset_fn:expr, vmsd => $vmsd:ident$(,)*) => {
-        pub unsafe extern "C" fn $func(
-            klass: *mut $crate::bindings::ObjectClass,
-            _: *mut ::std::os::raw::c_void,
-        ) {
-            let mut dc =
-                ::core::ptr::NonNull::new(klass.cast::<$crate::bindings::DeviceClass>()).unwrap();
-            unsafe {
-                dc.as_mut().realize = $realize_fn;
-                dc.as_mut().vmsd = &$vmsd;
-                $crate::bindings::device_class_set_legacy_reset(dc.as_mut(), $legacy_reset_fn);
-                $crate::bindings::device_class_set_props(dc.as_mut(), $props.as_ptr());
-            }
+macro_rules! impl_device_class {
+    ($type:ty) => {
+        impl $crate::definitions::ClassInitImpl for $type {
+            const CLASS_INIT: Option<
+                unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut ::std::os::raw::c_void),
+            > = Some($crate::device_class::rust_device_class_init::<$type>);
+            const CLASS_BASE_INIT: Option<
+                unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut ::std::os::raw::c_void),
+            > = None;
         }
     };
 }
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index fd0c979121..b8b12a4042 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -2,13 +2,14 @@
 // Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-use std::{ffi::CStr, os::raw::c_void};
+use std::ffi::CStr;
 
 use qemu_api::{
     bindings::*,
     c_str, declare_properties, define_property,
-    definitions::{ClassInitImpl, ObjectImpl},
-    device_class, device_class_init,
+    definitions::ObjectImpl,
+    device_class::{self, DeviceImpl},
+    impl_device_class,
     zeroable::Zeroable,
 };
 
@@ -45,28 +46,23 @@ fn test_device_decl_macros() {
             ),
     }
 
-    device_class_init! {
-        dummy_class_init,
-        props => DUMMY_PROPERTIES,
-        realize_fn => None,
-        legacy_reset_fn => None,
-        vmsd => VMSTATE,
-    }
-
     impl ObjectImpl for DummyState {
         type Class = DummyClass;
         const TYPE_NAME: &'static CStr = c_str!("dummy");
         const PARENT_TYPE_NAME: Option<&'static CStr> = Some(device_class::TYPE_DEVICE);
     }
 
-    impl ClassInitImpl for DummyState {
-        const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
-            Some(dummy_class_init);
-        const CLASS_BASE_INIT: Option<
-            unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void),
-        > = None;
+    impl DeviceImpl for DummyState {
+        fn properties() -> &'static [Property] {
+            &DUMMY_PROPERTIES
+        }
+        fn vmsd() -> Option<&'static VMStateDescription> {
+            Some(&VMSTATE)
+        }
     }
 
+    impl_device_class!(DummyState);
+
     unsafe {
         module_call_init(module_init_type::MODULE_INIT_QOM);
         object_unref(object_new(DummyState::TYPE_NAME.as_ptr()).cast());
-- 
cgit 1.4.1


From 7bd8e3ef63330e870cf4644d21c285cce35c703d Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 31 Oct 2024 09:56:15 +0100
Subject: rust: qom: split ObjectType from ObjectImpl trait

Define a separate trait for fields that also applies to classes that are
defined by C code.  This makes it possible to add metadata to core classes,
which has multiple uses:

- it makes it possible to access the parent struct's TYPE_* for types
  that are defined in Rust code, and to avoid repeating it in every subclass

- implementors of ObjectType will be allowed to implement the IsA<> trait and
  therefore to perform typesafe casts from one class to another.

- in the future, an ObjectType could be created with Foo::new() in a type-safe
  manner, without having to pass a TYPE_* constant.

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/char/pl011/src/device.rs  | 17 ++++++++++++-----
 rust/qemu-api/src/definitions.rs  | 27 +++++++++++++++++++++------
 rust/qemu-api/src/device_class.rs | 11 ++++++-----
 rust/qemu-api/src/prelude.rs      |  2 ++
 rust/qemu-api/src/sysbus.rs       | 10 ++++++++--
 rust/qemu-api/tests/tests.rs      | 17 +++++++++--------
 6 files changed, 58 insertions(+), 26 deletions(-)

(limited to 'rust/qemu-api/tests/tests.rs')

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index b9f8fb134b..0ab825b1ca 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -12,9 +12,10 @@ use qemu_api::{
     bindings::{self, *},
     c_str,
     definitions::ObjectImpl,
-    device_class::{DeviceImpl, TYPE_SYS_BUS_DEVICE},
+    device_class::DeviceImpl,
     impl_device_class,
     irq::InterruptSource,
+    prelude::*,
 };
 
 use crate::{
@@ -106,10 +107,13 @@ pub struct PL011State {
     device_id: DeviceId,
 }
 
-impl ObjectImpl for PL011State {
+unsafe impl ObjectType for PL011State {
     type Class = PL011Class;
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011;
-    const PARENT_TYPE_NAME: Option<&'static CStr> = Some(TYPE_SYS_BUS_DEVICE);
+}
+
+impl ObjectImpl for PL011State {
+    const PARENT_TYPE_NAME: Option<&'static CStr> = Some(<SysBusDevice as ObjectType>::TYPE_NAME);
     const INSTANCE_INIT: Option<unsafe fn(&mut Self)> = Some(Self::init);
 }
 
@@ -640,10 +644,13 @@ impl PL011Luminary {
     }
 }
 
-impl ObjectImpl for PL011Luminary {
+unsafe impl ObjectType for PL011Luminary {
     type Class = PL011LuminaryClass;
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011_LUMINARY;
-    const PARENT_TYPE_NAME: Option<&'static CStr> = Some(crate::TYPE_PL011);
+}
+
+impl ObjectImpl for PL011Luminary {
+    const PARENT_TYPE_NAME: Option<&'static CStr> = Some(<PL011State as ObjectType>::TYPE_NAME);
     const INSTANCE_INIT: Option<unsafe fn(&mut Self)> = Some(Self::init);
 }
 
diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
index f297075898..b98a692678 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -26,25 +26,40 @@ unsafe extern "C" fn rust_instance_post_init<T: ObjectImpl>(obj: *mut Object) {
     T::INSTANCE_POST_INIT.unwrap()(unsafe { &mut *obj.cast::<T>() })
 }
 
-/// Trait a type must implement to be registered with QEMU.
+/// Trait exposed by all structs corresponding to QOM objects.
 ///
 /// # Safety
 ///
-/// - the struct must be `#[repr(C)]`
+/// For classes declared in C:
+///
+/// - `Class` and `TYPE` must match the data in the `TypeInfo`;
+///
+/// - the first field of the struct must be of the instance type corresponding
+///   to the superclass, as declared in the `TypeInfo`
+///
+/// - likewise, the first field of the `Class` struct must be of the class type
+///   corresponding to the superclass
 ///
-/// - `Class` and `TYPE` must match the data in the `TypeInfo` (this is
-///   automatic if the class is defined via `ObjectImpl`).
+/// For classes declared in Rust and implementing [`ObjectImpl`]:
+///
+/// - the struct must be `#[repr(C)]`;
 ///
 /// - the first field of the struct must be of the instance struct corresponding
-///   to the superclass declared as `PARENT_TYPE_NAME`
-pub trait ObjectImpl: ClassInitImpl + Sized {
+///   to the superclass, as declared in `ObjectImpl::PARENT_TYPE_NAME`
+///
+/// - likewise, the first field of the `Class` must be of the class struct
+///   corresponding to the superclass
+pub unsafe trait ObjectType: Sized {
     /// The QOM class object corresponding to this struct.  Not used yet.
     type Class;
 
     /// The name of the type, which can be passed to `object_new()` to
     /// generate an instance of this type.
     const TYPE_NAME: &'static CStr;
+}
 
+/// Trait a type must implement to be registered with QEMU.
+pub trait ObjectImpl: ObjectType + ClassInitImpl {
     /// The parent of the type.  This should match the first field of
     /// the struct that implements `ObjectImpl`:
     const PARENT_TYPE_NAME: Option<&'static CStr>;
diff --git a/rust/qemu-api/src/device_class.rs b/rust/qemu-api/src/device_class.rs
index f25904be4f..03d03feee8 100644
--- a/rust/qemu-api/src/device_class.rs
+++ b/rust/qemu-api/src/device_class.rs
@@ -6,6 +6,7 @@ use std::{ffi::CStr, os::raw::c_void};
 
 use crate::{
     bindings::{self, DeviceClass, DeviceState, Error, ObjectClass, Property, VMStateDescription},
+    prelude::*,
     zeroable::Zeroable,
 };
 
@@ -146,8 +147,8 @@ macro_rules! declare_properties {
     };
 }
 
-// workaround until we can use --generate-cstr in bindgen.
-pub const TYPE_DEVICE: &CStr =
-    unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_DEVICE) };
-pub const TYPE_SYS_BUS_DEVICE: &CStr =
-    unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_SYS_BUS_DEVICE) };
+unsafe impl ObjectType for bindings::DeviceState {
+    type Class = bindings::DeviceClass;
+    const TYPE_NAME: &'static CStr =
+        unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_DEVICE) };
+}
diff --git a/rust/qemu-api/src/prelude.rs b/rust/qemu-api/src/prelude.rs
index a39e228bab..1b8677b2d9 100644
--- a/rust/qemu-api/src/prelude.rs
+++ b/rust/qemu-api/src/prelude.rs
@@ -6,3 +6,5 @@ pub use crate::bitops::IntegerExt;
 
 pub use crate::cell::BqlCell;
 pub use crate::cell::BqlRefCell;
+
+pub use crate::definitions::ObjectType;
diff --git a/rust/qemu-api/src/sysbus.rs b/rust/qemu-api/src/sysbus.rs
index 4e192c7589..5ee068541c 100644
--- a/rust/qemu-api/src/sysbus.rs
+++ b/rust/qemu-api/src/sysbus.rs
@@ -2,11 +2,17 @@
 // Author(s): Paolo Bonzini <pbonzini@redhat.com>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-use std::ptr::addr_of;
+use std::{ffi::CStr, ptr::addr_of};
 
 pub use bindings::{SysBusDevice, SysBusDeviceClass};
 
-use crate::{bindings, cell::bql_locked, irq::InterruptSource};
+use crate::{bindings, cell::bql_locked, irq::InterruptSource, prelude::*};
+
+unsafe impl ObjectType for SysBusDevice {
+    type Class = SysBusDeviceClass;
+    const TYPE_NAME: &'static CStr =
+        unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_SYS_BUS_DEVICE) };
+}
 
 impl SysBusDevice {
     /// Return `self` cast to a mutable pointer, for use in calls to C code.
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index b8b12a4042..1d027dd652 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -5,12 +5,8 @@
 use std::ffi::CStr;
 
 use qemu_api::{
-    bindings::*,
-    c_str, declare_properties, define_property,
-    definitions::ObjectImpl,
-    device_class::{self, DeviceImpl},
-    impl_device_class,
-    zeroable::Zeroable,
+    bindings::*, c_str, declare_properties, define_property, definitions::ObjectImpl,
+    device_class::DeviceImpl, impl_device_class, prelude::*, zeroable::Zeroable,
 };
 
 #[test]
@@ -46,10 +42,15 @@ fn test_device_decl_macros() {
             ),
     }
 
-    impl ObjectImpl for DummyState {
+    unsafe impl ObjectType for DummyState {
         type Class = DummyClass;
         const TYPE_NAME: &'static CStr = c_str!("dummy");
-        const PARENT_TYPE_NAME: Option<&'static CStr> = Some(device_class::TYPE_DEVICE);
+    }
+
+    impl ObjectImpl for DummyState {
+        const PARENT_TYPE_NAME: Option<&'static CStr> =
+            Some(<DeviceState as ObjectType>::TYPE_NAME);
+        const ABSTRACT: bool = false;
     }
 
     impl DeviceImpl for DummyState {
-- 
cgit 1.4.1


From 166e8a1fd15bfa527b25fc15ca315e572c0556d2 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Sun, 24 Nov 2024 18:51:34 +0100
Subject: rust: qom: change the parent type to an associated type

Avoid duplicated code to retrieve the QOM type strings from the
Rust type.

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/char/pl011/src/device.rs |  6 ++++--
 rust/qemu-api/src/definitions.rs | 12 ++++--------
 rust/qemu-api/tests/tests.rs     |  3 +--
 3 files changed, 9 insertions(+), 12 deletions(-)

(limited to 'rust/qemu-api/tests/tests.rs')

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index 0ab825b1ca..3e29442a62 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -113,7 +113,8 @@ unsafe impl ObjectType for PL011State {
 }
 
 impl ObjectImpl for PL011State {
-    const PARENT_TYPE_NAME: Option<&'static CStr> = Some(<SysBusDevice as ObjectType>::TYPE_NAME);
+    type ParentType = SysBusDevice;
+
     const INSTANCE_INIT: Option<unsafe fn(&mut Self)> = Some(Self::init);
 }
 
@@ -650,7 +651,8 @@ unsafe impl ObjectType for PL011Luminary {
 }
 
 impl ObjectImpl for PL011Luminary {
-    const PARENT_TYPE_NAME: Option<&'static CStr> = Some(<PL011State as ObjectType>::TYPE_NAME);
+    type ParentType = PL011State;
+
     const INSTANCE_INIT: Option<unsafe fn(&mut Self)> = Some(Self::init);
 }
 
diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
index b98a692678..df91a2e31a 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -45,10 +45,10 @@ unsafe extern "C" fn rust_instance_post_init<T: ObjectImpl>(obj: *mut Object) {
 /// - the struct must be `#[repr(C)]`;
 ///
 /// - the first field of the struct must be of the instance struct corresponding
-///   to the superclass, as declared in `ObjectImpl::PARENT_TYPE_NAME`
+///   to the superclass, which is `ObjectImpl::ParentType`
 ///
 /// - likewise, the first field of the `Class` must be of the class struct
-///   corresponding to the superclass
+///   corresponding to the superclass, which is `ObjectImpl::ParentType::Class`.
 pub unsafe trait ObjectType: Sized {
     /// The QOM class object corresponding to this struct.  Not used yet.
     type Class;
@@ -62,7 +62,7 @@ pub unsafe trait ObjectType: Sized {
 pub trait ObjectImpl: ObjectType + ClassInitImpl {
     /// The parent of the type.  This should match the first field of
     /// the struct that implements `ObjectImpl`:
-    const PARENT_TYPE_NAME: Option<&'static CStr>;
+    type ParentType: ObjectType;
 
     /// Whether the object can be instantiated
     const ABSTRACT: bool = false;
@@ -82,11 +82,7 @@ pub trait ObjectImpl: ObjectType + ClassInitImpl {
 
     const TYPE_INFO: TypeInfo = TypeInfo {
         name: Self::TYPE_NAME.as_ptr(),
-        parent: if let Some(pname) = Self::PARENT_TYPE_NAME {
-            pname.as_ptr()
-        } else {
-            core::ptr::null_mut()
-        },
+        parent: Self::ParentType::TYPE_NAME.as_ptr(),
         instance_size: core::mem::size_of::<Self>(),
         instance_align: core::mem::align_of::<Self>(),
         instance_init: match Self::INSTANCE_INIT {
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index 1d027dd652..278efe967f 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -48,8 +48,7 @@ fn test_device_decl_macros() {
     }
 
     impl ObjectImpl for DummyState {
-        const PARENT_TYPE_NAME: Option<&'static CStr> =
-            Some(<DeviceState as ObjectType>::TYPE_NAME);
+        type ParentType = DeviceState;
         const ABSTRACT: bool = false;
     }
 
-- 
cgit 1.4.1