From 201ef001dd40fdb11c83f3e47604219c374590ec Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 17 Jan 2025 11:21:26 +0100
Subject: rust: qdev: add clock creation

Add a Rust version of qdev_init_clock_in, which can be used in
instance_init.  There are a couple differences with the C
version:

- in Rust the object keeps its own reference to the clock (in addition to
  the one embedded in the NamedClockList), and the reference is dropped
  automatically by instance_finalize(); this is encoded in the signature
  of DeviceClassMethods::init_clock_in, which makes the lifetime of the
  clock independent of that of the object it holds.  This goes unnoticed
  in the C version and is due to the existence of aliases.

- also, anything that happens during instance_init uses the pinned_init
  framework to operate on a partially initialized object, and is done
  through class methods (i.e. through DeviceClassMethods rather than
  DeviceMethods) because the device does not exist yet.  Therefore, Rust
  code *must* create clocks from instance_init, which is stricter than C.

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/char/pl011/src/device.rs | 43 ++++++++++++++++------------------------
 1 file changed, 17 insertions(+), 26 deletions(-)

(limited to 'rust/hw')

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index f5db114..37936a3 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -10,17 +10,16 @@ use std::{
 
 use qemu_api::{
     bindings::{
-        error_fatal, hwaddr, memory_region_init_io, qdev_init_clock_in, qdev_prop_set_chr,
-        qemu_chr_fe_accept_input, qemu_chr_fe_ioctl, qemu_chr_fe_set_handlers,
-        qemu_chr_fe_write_all, qemu_irq, sysbus_connect_irq, sysbus_mmio_map, sysbus_realize,
-        CharBackend, Chardev, Clock, ClockEvent, MemoryRegion, QEMUChrEvent,
-        CHR_IOCTL_SERIAL_SET_BREAK,
+        error_fatal, hwaddr, memory_region_init_io, qdev_prop_set_chr, qemu_chr_fe_accept_input,
+        qemu_chr_fe_ioctl, qemu_chr_fe_set_handlers, qemu_chr_fe_write_all, qemu_irq,
+        sysbus_connect_irq, sysbus_mmio_map, sysbus_realize, CharBackend, Chardev, MemoryRegion,
+        QEMUChrEvent, CHR_IOCTL_SERIAL_SET_BREAK,
     },
     c_str, impl_vmstate_forward,
     irq::InterruptSource,
     prelude::*,
-    qdev::{DeviceImpl, DeviceState, Property},
-    qom::{ClassInitImpl, ObjectImpl, ParentField},
+    qdev::{Clock, ClockEvent, DeviceImpl, DeviceState, Property},
+    qom::{ClassInitImpl, ObjectImpl, Owned, ParentField},
     sysbus::{SysBusDevice, SysBusDeviceClass},
     vmstate::VMStateDescription,
 };
@@ -131,7 +130,7 @@ pub struct PL011State {
     #[doc(alias = "irq")]
     pub interrupts: [InterruptSource; IRQMASK.len()],
     #[doc(alias = "clk")]
-    pub clock: NonNull<Clock>,
+    pub clock: Owned<Clock>,
     #[doc(alias = "migrate_clk")]
     pub migrate_clock: bool,
 }
@@ -485,8 +484,6 @@ impl PL011State {
     /// location/instance. All its fields are expected to hold unitialized
     /// values with the sole exception of `parent_obj`.
     unsafe fn init(&mut self) {
-        const CLK_NAME: &CStr = c_str!("clk");
-
         // SAFETY:
         //
         // self and self.iomem are guaranteed to be valid at this point since callers
@@ -506,22 +503,16 @@ impl PL011State {
 
         // SAFETY:
         //
-        // self.clock is not initialized at this point; but since `NonNull<_>` is Copy,
-        // we can overwrite the undefined value without side effects. This is
-        // safe since all PL011State instances are created by QOM code which
-        // calls this function to initialize the fields; therefore no code is
-        // able to access an invalid self.clock value.
-        unsafe {
-            let dev: &mut DeviceState = self.upcast_mut();
-            self.clock = NonNull::new(qdev_init_clock_in(
-                dev,
-                CLK_NAME.as_ptr(),
-                None, /* pl011_clock_update */
-                addr_of_mut!(*self).cast::<c_void>(),
-                ClockEvent::ClockUpdate.0,
-            ))
-            .unwrap();
-        }
+        // self.clock is not initialized at this point; but since `Owned<_>` is
+        // not Drop, we can overwrite the undefined value without side effects;
+        // it's not sound but, because for all PL011State instances are created
+        // by QOM code which calls this function to initialize the fields, at
+        // leastno code is able to access an invalid self.clock value.
+        self.clock = self.init_clock_in("clk", &Self::clock_update, ClockEvent::ClockUpdate);
+    }
+
+    const fn clock_update(&self, _event: ClockEvent) {
+        /* pl011_trace_baudrate_change(s); */
     }
 
     fn post_init(&self) {
-- 
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