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rust: qom: add ObjectImpl::CLASS_INIT

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As shown in the PL011 device, the orphan rules required a manual
implementation of ClassInitImpl for anything not in the qemu_api crate;
this gets in the way of moving system emulation-specific code (including
DeviceClass, which as a blanket ClassInitImpl<DeviceClass> implementation)
into its own crate.

Make ClassInitImpl optional, at the cost of having to specify the CLASS_INIT
member by hand in every implementation of ObjectImpl.  The next commits will
get rid of it, replacing all the "impl<T> ClassInitImpl<Class> for T" blocks
with a generic class_init<T> method on Class.

Right now the definition is always the same, but do not provide a default
as that will not be true once ClassInitImpl goes away.

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2025-02-12 11:49:32 +01:00
parent 3212da0033
commit 4551f342fe
4 changed files with 19 additions and 4 deletions
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14
rust/qemu-api/src/qom.rs
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@ -180,7 +180,7 @@ unsafe extern "C" fn rust_instance_post_init<T: ObjectImpl>(obj: *mut Object) {
T::INSTANCE_POST_INIT.unwrap()(unsafe { state.as_ref() });
}
unsafe extern "C" fn rust_class_init<T: ObjectType + ClassInitImpl<T::Class>>(
unsafe extern "C" fn rust_class_init<T: ObjectType + ObjectImpl>(
klass: *mut ObjectClass,
_data: *mut c_void,
) {
@ -190,7 +190,7 @@ unsafe extern "C" fn rust_class_init<T: ObjectType + ClassInitImpl<T::Class>>(
// SAFETY: klass is a T::Class, since rust_class_init<T>
// is called from QOM core as the class_init function
// for class T
T::class_init(unsafe { klass.as_mut() })
<T as ObjectImpl>::CLASS_INIT(unsafe { klass.as_mut() })
}
unsafe extern "C" fn drop_object<T: ObjectImpl>(obj: *mut Object) {
@ -499,7 +499,7 @@ 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 + ClassInitImpl<Self::Class> + IsA<Object> {
pub trait ObjectImpl: ObjectType + IsA<Object> {
/// The parent of the type. This should match the first field of the
/// struct that implements `ObjectImpl`, minus the `ParentField<_>` wrapper.
type ParentType: ObjectType;
@ -552,6 +552,14 @@ pub trait ObjectImpl: ObjectType + ClassInitImpl<Self::Class> + IsA<Object> {
// methods on ObjectClass
const UNPARENT: Option<fn(&Self)> = None;
/// Store into the argument the virtual method implementations
/// for `Self`. 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.
///
/// Usually defined as `<Self as ClassInitImpl<Self::Class>::class_init`.
const CLASS_INIT: fn(&mut Self::Class);
}
/// Internal trait used to automatically fill in a class struct.