[PULL 49/49] rust: qom: change the parent type to an associated type

[Paolo Bonzini]

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

Reviewed-by: Zhao Liu <zhao1....@intel.com>
Signed-off-by: Paolo Bonzini <pbonz...@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(-)

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index 0ab825b1ca4..3e29442a625 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 b98a6926785..df91a2e31a9 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -45,10 +45,10 @@
 /// - 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 1d027dd6527..278efe967fe 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -48,8 +48,7 @@ unsafe impl ObjectType for DummyState {
     }
 
     impl ObjectImpl for DummyState {
-        const PARENT_TYPE_NAME: Option<&'static CStr> =
-            Some(<DeviceState as ObjectType>::TYPE_NAME);
+        type ParentType = DeviceState;
         const ABSTRACT: bool = false;
     }
 
-- 
2.47.1