[PATCH v2 06/10] rust: add bindings for timer

[Zhao Liu <zhao1.liu@intel.com>]

Add timer bindings to help handle idiomatic Rust callbacks.

Additionally, wrap QEMUClockType in ClockType binding to avoid unsafe
calls in device code.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
Changes since RFC:
 * Use FnCall to support timer callback.
 * Only add timer_init_full() binding. timer_new() is unnecessary since
   device (HPET) could create and allocate QEMUTimer.
 * Implement Drop for QEMUTimer.
 * Add ClockType binding.

Changes since Patch v1:
 * Use Timer/TimerListGroup in Rust code instead of
   QEMUTimer/QEMUTimerListGroup.
 * Rename timer_init_full()/timer_mod() to init_full()/modify().
 * Ensure the callback passed to Timer::init() is not none.
 * Add as_mut_ptr()/delete() method for Timer.
 * Make ClockType's `id` field private, as well as make Timer::init()
   accept ClockType instead of QEMUClockType.
 * Drop used qemu_clock_get_virtual_ns().
 * Add MS/US/NS wrappers.
---
 meson.build                |  7 +++
 rust/qemu-api/meson.build  |  1 +
 rust/qemu-api/src/lib.rs   |  1 +
 rust/qemu-api/src/timer.rs | 98 ++++++++++++++++++++++++++++++++++++++
 rust/wrapper.h             |  1 +
 5 files changed, 108 insertions(+)
 create mode 100644 rust/qemu-api/src/timer.rs

diff --git a/meson.build b/meson.build
index 32abefb7c48c..20192347d4d6 100644
--- a/meson.build
+++ b/meson.build
@@ -4086,6 +4086,13 @@ if have_rust
   foreach enum : c_bitfields
     bindgen_args += ['--bitfield-enum', enum]
   endforeach
+  c_nocopy = [
+    'QEMUTimer',
+  ]
+  # Used to customize Drop trait
+  foreach struct : c_nocopy
+    bindgen_args += ['--no-copy', struct]
+  endforeach
 
   # TODO: Remove this comment when the clang/libclang mismatch issue is solved.
   #
diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index 45e30324b295..2e9c1078b9b2 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -30,6 +30,7 @@ _qemu_api_rs = static_library(
       'src/qdev.rs',
       'src/qom.rs',
       'src/sysbus.rs',
+      'src/timer.rs',
       'src/vmstate.rs',
       'src/zeroable.rs',
     ],
diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
index 1d7112445e24..047511d36487 100644
--- a/rust/qemu-api/src/lib.rs
+++ b/rust/qemu-api/src/lib.rs
@@ -25,6 +25,7 @@
 pub mod qdev;
 pub mod qom;
 pub mod sysbus;
+pub mod timer;
 pub mod vmstate;
 pub mod zeroable;
 
diff --git a/rust/qemu-api/src/timer.rs b/rust/qemu-api/src/timer.rs
new file mode 100644
index 000000000000..05a5061b6dda
--- /dev/null
+++ b/rust/qemu-api/src/timer.rs
@@ -0,0 +1,98 @@
+// Copyright (C) 2024 Intel Corporation.
+// Author(s): Zhao Liu <zhai1.liu@intel.com>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+use std::os::raw::{c_int, c_void};
+
+use crate::{
+    bindings::{self, qemu_clock_get_ns, timer_del, timer_init_full, timer_mod, QEMUClockType},
+    callbacks::FnCall,
+};
+
+pub type Timer = bindings::QEMUTimer;
+pub type TimerListGroup = bindings::QEMUTimerListGroup;
+
+impl Timer {
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    const fn as_mut_ptr(&self) -> *mut Self {
+        self as *const Timer as *mut _
+    }
+
+    pub fn init_full<'timer, 'opaque: 'timer, T, F>(
+        &'timer mut self,
+        timer_list_group: Option<&TimerListGroup>,
+        clk_type: ClockType,
+        scale: u32,
+        attributes: u32,
+        _cb: F,
+        opaque: &'opaque T,
+    ) where
+        F: for<'a> FnCall<(&'a T,)>,
+    {
+        let _: () = F::ASSERT_IS_SOME;
+
+        /// timer expiration callback
+        unsafe extern "C" fn rust_timer_handler<T, F: for<'a> FnCall<(&'a T,)>>(
+            opaque: *mut c_void,
+        ) {
+            // SAFETY: the opaque was passed as a reference to `T`.
+            F::call((unsafe { &*(opaque.cast::<T>()) },))
+        }
+
+        let timer_cb: unsafe extern "C" fn(*mut c_void) = rust_timer_handler::<T, F>;
+
+        // SAFETY: the opaque outlives the timer
+        unsafe {
+            timer_init_full(
+                self,
+                if let Some(g) = timer_list_group {
+                    g as *const TimerListGroup as *mut _
+                } else {
+                    ::core::ptr::null_mut()
+                },
+                clk_type.id,
+                scale as c_int,
+                attributes as c_int,
+                Some(timer_cb),
+                (opaque as *const T).cast::<c_void>() as *mut c_void,
+            )
+        }
+    }
+
+    pub fn modify(&self, expire_time: u64) {
+        unsafe { timer_mod(self.as_mut_ptr(), expire_time as i64) }
+    }
+
+    pub fn delete(&self) {
+        unsafe { timer_del(self.as_mut_ptr()) }
+    }
+}
+
+impl Drop for Timer {
+    fn drop(&mut self) {
+        self.delete()
+    }
+}
+
+pub struct ClockType {
+    id: QEMUClockType,
+}
+
+impl ClockType {
+    pub fn get_ns(&self) -> u64 {
+        // SAFETY: cannot be created outside this module, therefore id
+        // is valid
+        (unsafe { qemu_clock_get_ns(self.id) }) as u64
+    }
+}
+
+pub const CLOCK_VIRTUAL: ClockType = ClockType {
+    id: QEMUClockType::QEMU_CLOCK_VIRTUAL,
+};
+
+pub const MS: u32 = bindings::SCALE_MS;
+pub const US: u32 = bindings::SCALE_US;
+pub const NS: u32 = bindings::SCALE_NS;
diff --git a/rust/wrapper.h b/rust/wrapper.h
index 54839ce0f510..a35bfbd1760d 100644
--- a/rust/wrapper.h
+++ b/rust/wrapper.h
@@ -63,3 +63,4 @@ typedef enum memory_order {
 #include "migration/vmstate.h"
 #include "chardev/char-serial.h"
 #include "exec/memattrs.h"
+#include "qemu/timer.h"
-- 
2.34.1