motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-07-27 04:13:53 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

rust: qom: get rid of ClassInitImpl

Browse source 
Complete the conversion from the ClassInitImpl trait to class_init() methods.
This will provide more freedom to split the qemu_api crate in separate parts.

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2025-02-13 12:37:43 +01:00
parent 567c0c41a6
commit d556226d69
6 changed files with 101 additions and 130 deletions
Download patch file Download diff file Expand all files Collapse all files

38
rust/qemu-api/src/qdev.rs
View file

@ -19,7 +19,7 @@ use crate::{
chardev::Chardev,
irq::InterruptSource,
prelude::*,
qom::{ClassInitImpl, ObjectClass, ObjectImpl, Owned},
qom::{ObjectClass, ObjectImpl, Owned},
vmstate::VMStateDescription,
};
@ -113,7 +113,7 @@ pub trait DeviceImpl: ObjectImpl + ResettablePhasesImpl + IsA<DeviceState> {
/// # Safety
///
/// This function is only called through the QOM machinery and
/// used by the `ClassInitImpl<DeviceClass>` trait.
/// used by `DeviceClass::class_init`.
/// 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.
@ -127,43 +127,41 @@ unsafe impl InterfaceType for ResettableClass {
unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_RESETTABLE_INTERFACE) };
}
impl<T> ClassInitImpl<ResettableClass> for T
where
T: ResettablePhasesImpl,
{
fn class_init(rc: &mut ResettableClass) {
impl ResettableClass {
/// Fill in the virtual methods of `ResettableClass` based on the
/// definitions in the `ResettablePhasesImpl` trait.
pub fn class_init<T: ResettablePhasesImpl>(&mut self) {
if <T as ResettablePhasesImpl>::ENTER.is_some() {
rc.phases.enter = Some(rust_resettable_enter_fn::<T>);
self.phases.enter = Some(rust_resettable_enter_fn::<T>);
}
if <T as ResettablePhasesImpl>::HOLD.is_some() {
rc.phases.hold = Some(rust_resettable_hold_fn::<T>);
self.phases.hold = Some(rust_resettable_hold_fn::<T>);
}
if <T as ResettablePhasesImpl>::EXIT.is_some() {
rc.phases.exit = Some(rust_resettable_exit_fn::<T>);
self.phases.exit = Some(rust_resettable_exit_fn::<T>);
}
}
}
impl<T> ClassInitImpl<DeviceClass> for T
where
T: ClassInitImpl<ObjectClass> + ClassInitImpl<ResettableClass> + DeviceImpl,
{
fn class_init(dc: &mut DeviceClass) {
impl DeviceClass {
/// Fill in the virtual methods of `DeviceClass` based on the definitions in
/// the `DeviceImpl` trait.
pub fn class_init<T: DeviceImpl>(&mut self) {
if <T as DeviceImpl>::REALIZE.is_some() {
dc.realize = Some(rust_realize_fn::<T>);
self.realize = Some(rust_realize_fn::<T>);
}
if let Some(vmsd) = <T as DeviceImpl>::vmsd() {
dc.vmsd = vmsd;
self.vmsd = vmsd;
}
let prop = <T as DeviceImpl>::properties();
if !prop.is_empty() {
unsafe {
bindings::device_class_set_props_n(dc, prop.as_ptr(), prop.len());
bindings::device_class_set_props_n(self, prop.as_ptr(), prop.len());
}
}
ResettableClass::interface_init::<T, DeviceState>(dc);
<T as ClassInitImpl<ObjectClass>>::class_init(&mut dc.parent_class);
ResettableClass::cast::<DeviceState>(self).class_init::<T>();
self.parent_class.class_init::<T>();
}
}

164
rust/qemu-api/src/qom.rs
View file

@ -40,11 +40,6 @@
//! The traits have the appropriate specialization of `IsA<>` as a supertrait,
//! for example `IsA<DeviceState>` for `DeviceImpl`.
//!
//! * an implementation of [`ClassInitImpl`], for example
//! `ClassInitImpl<DeviceClass>`. This fills the vtable in the class struct;
//! the source for this is the `*Impl` trait; the associated consts and
//! functions if needed are wrapped to map C types into Rust types.
//!
//! * a trait for instance methods, for example `DeviceMethods`. This trait is
//! automatically implemented for any reference or smart pointer to a device
//! instance. It calls into the vtable provides access across all subclasses
@ -54,6 +49,48 @@
//! This provides access to class-wide functionality that doesn't depend on
//! instance data. Like instance methods, these are automatically inherited by
//! child classes.
//!
//! # Class structures
//!
//! 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`].
//!
//! As mentioned above, virtual methods are defined via traits such as
//! `DeviceImpl`. Class structs do not define any trait but, conventionally,
//! all of them have a `class_init` method to initialize the virtual methods
//! based on the trait and then call the same method on the superclass.
//!
//! ```ignore
//! impl YourSubclassClass
//! {
//! pub fn class_init<T: YourSubclassImpl>(&mut self) {
//! ...
//! klass.parent_class::class_init<T>();
//! }
//! }
//! ```
//!
//! If a class implements a QOM interface. In that case, the function must
//! contain, for each interface, an extra forwarding call as follows:
//!
//! ```ignore
//! ResettableClass::cast::<Self>(self).class_init::<Self>();
//! ```
//!
//! These `class_init` functions are methods on the class rather than a trait,
//! because the bound on `T` (`DeviceImpl` in this case), will change for every
//! class struct. The functions are pointed to by the
//! [`ObjectImpl::CLASS_INIT`] function pointer. While there is no default
//! implementation, in most cases it will be enough to write it as follows:
//!
//! ```ignore
//! const CLASS_INIT: fn(&mut Self::Class)> = Self::Class::class_init::<Self>;
//! ```
//!
//! This design incurs a small amount of code duplication but, by not using
//! traits, it allows the flexibility of implementing bindings in any crate,
//! without incurring into violations of orphan rules for traits.
use std::{
ffi::CStr,
@ -279,19 +316,25 @@ pub unsafe trait InterfaceType: Sized {
/// for this interface.
const TYPE_NAME: &'static CStr;
/// Initialize the vtable for the interface; the generic argument `T` is the
/// type being initialized, while the generic argument `U` is the type that
/// Return the vtable for the interface; `U` is the type that
/// lists the interface in its `TypeInfo`.
///
/// # Examples
///
/// This function is usually called by a `class_init` method in `U::Class`.
/// For example, `DeviceClass::class_init<T>` initializes its `Resettable`
/// interface as follows:
///
/// ```ignore
/// ResettableClass::cast::<DeviceState>(self).class_init::<T>();
/// ```
///
/// where `T` is the concrete subclass that is being initialized.
///
/// # Panics
///
/// Panic if the incoming argument if `T` does not implement the interface.
fn interface_init<
T: ObjectType + ClassInitImpl<Self> + ClassInitImpl<U::Class>,
U: ObjectType,
>(
klass: &mut U::Class,
) {
fn cast<U: ObjectType>(klass: &mut U::Class) -> &mut Self {
unsafe {
// SAFETY: upcasting to ObjectClass is always valid, and the
// return type is either NULL or the argument itself
@ -300,8 +343,7 @@ pub unsafe trait InterfaceType: Sized {
Self::TYPE_NAME.as_ptr(),
)
.cast();
<T as ClassInitImpl<Self>>::class_init(result.as_mut().unwrap())
result.as_mut().unwrap()
}
}
}
@ -558,87 +600,20 @@ pub trait ObjectImpl: ObjectType + IsA<Object> {
/// 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.
///
/// 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; this trait takes care of
/// initializing the `T` part of the class struct, for the type that
/// implements the trait.
///
/// Each struct will implement this trait with `T` equal to each
/// superclass. For example, a device should implement at least
/// `ClassInitImpl<`[`DeviceClass`](crate::qdev::DeviceClass)`>` and
/// `ClassInitImpl<`[`ObjectClass`]`>`. Such implementations are made
/// in one of two ways.
///
/// For most superclasses, `ClassInitImpl` is provided by the `qemu-api`
/// crate itself. The Rust implementation of methods will come from a
/// trait like [`ObjectImpl`] or [`DeviceImpl`](crate::qdev::DeviceImpl),
/// and `ClassInitImpl` is provided by blanket implementations that
/// operate on all implementors of the `*Impl`* trait. For example:
///
/// ```ignore
/// impl<T> ClassInitImpl<DeviceClass> for T
/// where
/// T: ClassInitImpl<ObjectClass> + DeviceImpl,
/// ```
///
/// The bound on `ClassInitImpl<ObjectClass>` is needed so that,
/// after initializing the `DeviceClass` part of the class struct,
/// the parent [`ObjectClass`] is initialized as well.
///
/// The other case is when manual implementation of the trait is needed.
/// This covers the following cases:
///
/// * if a class implements a QOM interface, the Rust code _has_ to define its
/// own class struct `FooClass` and implement `ClassInitImpl<FooClass>`.
/// `ClassInitImpl<FooClass>`'s `class_init` method will then forward to
/// multiple other `class_init`s, for the interfaces as well as the
/// superclass. (Note that there is no Rust example yet for using interfaces).
///
/// * for classes implemented outside the ``qemu-api`` crate, it's not possible
/// to add blanket implementations like the above one, due to orphan rules. In
/// that case, the easiest solution is to implement
/// `ClassInitImpl<YourSuperclass>` for each subclass and not have a
/// `YourSuperclassImpl` trait at all.
///
/// ```ignore
/// impl ClassInitImpl<YourSuperclass> for YourSubclass {
/// fn class_init(klass: &mut YourSuperclass) {
/// klass.some_method = Some(Self::some_method);
/// <Self as ClassInitImpl<SysBusDeviceClass>>::class_init(&mut klass.parent_class);
/// }
/// }
/// ```
///
/// While this method incurs a small amount of code duplication,
/// it is generally limited to the recursive call on the last line.
/// This is because classes defined in Rust do not need the same
/// glue code that is needed when the classes are defined in C code.
/// You may consider using a macro if you have many subclasses.
pub trait ClassInitImpl<T> {
/// Initialize `klass` to point to 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 simply as `Self::Class::class_init::<Self>`;
/// however a default implementation cannot be included here, because the
/// bounds that the `Self::Class::class_init` method places on `Self` are
/// not known in advance.
///
/// The virtual method implementations usually come from another
/// trait, for example [`DeviceImpl`](crate::qdev::DeviceImpl)
/// when `T` is [`DeviceClass`](crate::qdev::DeviceClass).
/// # Safety
///
/// On entry, `klass`'s parent class is initialized, while the other fields
/// While `klass`'s parent class is initialized on entry, the other fields
/// are all zero; it is therefore assumed that all fields in `T` can be
/// zeroed, otherwise it would not be possible to provide the class as a
/// `&mut T`. TODO: add a bound of [`Zeroable`](crate::zeroable::Zeroable)
/// to T; this is more easily done once Zeroable does not require a manual
/// implementation (Rust 1.75.0).
fn class_init(klass: &mut T);
const CLASS_INIT: fn(&mut Self::Class);
}
/// # Safety
@ -651,13 +626,12 @@ unsafe extern "C" fn rust_unparent_fn<T: ObjectImpl>(dev: *mut Object) {
T::UNPARENT.unwrap()(unsafe { state.as_ref() });
}
impl<T> ClassInitImpl<ObjectClass> for T
where
T: ObjectImpl,
{
fn class_init(oc: &mut ObjectClass) {
impl ObjectClass {
/// Fill in the virtual methods of `ObjectClass` based on the definitions in
/// the `ObjectImpl` trait.
pub fn class_init<T: ObjectImpl>(&mut self) {
if <T as ObjectImpl>::UNPARENT.is_some() {
oc.unparent = Some(rust_unparent_fn::<T>);
self.unparent = Some(rust_unparent_fn::<T>);
}
}
}

15
rust/qemu-api/src/sysbus.rs
View file

@ -14,8 +14,8 @@ use crate::{
irq::{IRQState, InterruptSource},
memory::MemoryRegion,
prelude::*,
qdev::{DeviceClass, DeviceImpl, DeviceState},
qom::{ClassInitImpl, Owned},
qdev::{DeviceImpl, DeviceState},
qom::Owned,
};
unsafe impl ObjectType for SysBusDevice {
@ -28,12 +28,11 @@ qom_isa!(SysBusDevice: DeviceState, Object);
// TODO: add virtual methods
pub trait SysBusDeviceImpl: DeviceImpl + IsA<SysBusDevice> {}
impl<T> ClassInitImpl<SysBusDeviceClass> for T
where
T: SysBusDeviceImpl + ClassInitImpl<DeviceClass>,
{
fn class_init(sdc: &mut SysBusDeviceClass) {
<T as ClassInitImpl<DeviceClass>>::class_init(&mut sdc.parent_class);
impl SysBusDeviceClass {
/// Fill in the virtual methods of `SysBusDeviceClass` based on the
/// definitions in the `SysBusDeviceImpl` trait.
pub fn class_init<T: SysBusDeviceImpl>(self: &mut SysBusDeviceClass) {
self.parent_class.class_init::<T>();
}
}