rust: qom: put class_init together from multiple ClassInitImpl<>

Parameterize the implementation of ClassInitImpl so that it is
possible to call up the chain of implementations, one superclass at
a time starting at ClassInitImpl<Self::Class>.

In order to avoid having to implement (for example)
ClassInitImpl<PL011Class>, also remove the dummy PL011Class and
PL011LuminaryClass structs and specify the same ObjectType::Class as
the superclass.  In the future this default behavior can be handled by
a procedural macro, by looking at the first field in the struct.

Note that the new trait is safe: the calls are started by
rust_class_init<>(), which is not public and can convert the class
pointer to a Rust reference.

Since CLASS_BASE_INIT applies to the type that is being defined,
and only to it, move it to ObjectImpl.

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 17 deletions

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index 3e29442a62..d9e9f35f45 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -13,7 +13,6 @@ use qemu_api::{
     c_str,
     definitions::ObjectImpl,
     device_class::DeviceImpl,
-    impl_device_class,
     irq::InterruptSource,
     prelude::*,
 };
@@ -108,7 +107,7 @@ pub struct PL011State {
 }
 
 unsafe impl ObjectType for PL011State {
-    type Class = PL011Class;
+    type Class = <SysBusDevice as ObjectType>::Class;
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011;
 }
 
@@ -118,11 +117,6 @@ impl ObjectImpl for PL011State {
     const INSTANCE_INIT: Option<unsafe fn(&mut Self)> = Some(Self::init);
 }
 
-#[repr(C)]
-pub struct PL011Class {
-    _inner: [u8; 0],
-}
-
 impl DeviceImpl for PL011State {
     fn properties() -> &'static [Property] {
         &device_class::PL011_PROPERTIES
@@ -134,8 +128,6 @@ impl DeviceImpl for PL011State {
     const RESET: Option<fn(&mut Self)> = Some(Self::reset);
 }
 
-impl_device_class!(PL011State);
-
 impl PL011State {
     /// Initializes a pre-allocated, unitialized instance of `PL011State`.
     ///
@@ -627,11 +619,6 @@ pub struct PL011Luminary {
     parent_obj: PL011State,
 }
 
-#[repr(C)]
-pub struct PL011LuminaryClass {
-    _inner: [u8; 0],
-}
-
 impl PL011Luminary {
     /// Initializes a pre-allocated, unitialized instance of `PL011Luminary`.
     ///
@@ -646,7 +633,7 @@ impl PL011Luminary {
 }
 
 unsafe impl ObjectType for PL011Luminary {
-    type Class = PL011LuminaryClass;
+    type Class = <PL011State as ObjectType>::Class;
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011_LUMINARY;
 }
 
@@ -657,5 +644,3 @@ impl ObjectImpl for PL011Luminary {
 }
 
 impl DeviceImpl for PL011Luminary {}
-
-impl_device_class!(PL011Luminary);