rust: qom: move device_id to PL011 class side

There is no need to monkeypatch DeviceId::Luminary into the already-initialized
PL011State.  Instead, now that we can define a class hierarchy, we can define
PL011Class and make device_id a field in there.

There is also no need anymore to have "Arm" as zero, so change DeviceId into a
wrapper for the array; all it does is provide an Index<hwaddr> implementation
because arrays can only be indexed by usize.

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

rust/hw/char/pl011/src/device.rs

@@ -5,7 +5,7 @@
 use core::ptr::{addr_of_mut, NonNull};
 use std::{
     ffi::CStr,
-    os::raw::{c_int, c_uchar, c_uint, c_void},
+    os::raw::{c_int, c_uint, c_void},
 };
 
 use qemu_api::{
@@ -14,7 +14,7 @@ use qemu_api::{
     irq::InterruptSource,
     prelude::*,
     qdev::DeviceImpl,
-    qom::{ObjectImpl, ParentField},
+    qom::{ClassInitImpl, ObjectImpl, ParentField},
 };
 
 use crate::{
@@ -33,27 +33,20 @@ const FBRD_MASK: u32 = 0x3f;
 /// QEMU sourced constant.
 pub const PL011_FIFO_DEPTH: u32 = 16;
 
-#[derive(Clone, Copy, Debug)]
-enum DeviceId {
-    #[allow(dead_code)]
-    Arm = 0,
-    Luminary,
-}
+#[derive(Clone, Copy)]
+struct DeviceId(&'static [u8; 8]);
 
 impl std::ops::Index<hwaddr> for DeviceId {
-    type Output = c_uchar;
+    type Output = u8;
 
     fn index(&self, idx: hwaddr) -> &Self::Output {
-        match self {
-            Self::Arm => &Self::PL011_ID_ARM[idx as usize],
-            Self::Luminary => &Self::PL011_ID_LUMINARY[idx as usize],
-        }
+        &self.0[idx as usize]
     }
 }
 
 impl DeviceId {
-    const PL011_ID_ARM: [c_uchar; 8] = [0x11, 0x10, 0x14, 0x00, 0x0d, 0xf0, 0x05, 0xb1];
-    const PL011_ID_LUMINARY: [c_uchar; 8] = [0x11, 0x00, 0x18, 0x01, 0x0d, 0xf0, 0x05, 0xb1];
+    const ARM: Self = Self(&[0x11, 0x10, 0x14, 0x00, 0x0d, 0xf0, 0x05, 0xb1]);
+    const LUMINARY: Self = Self(&[0x11, 0x00, 0x18, 0x01, 0x0d, 0xf0, 0x05, 0xb1]);
 }
 
 // FIFOs use 32-bit indices instead of usize, for compatibility with
@@ -126,17 +119,28 @@ pub struct PL011State {
     pub clock: NonNull<Clock>,
     #[doc(alias = "migrate_clk")]
     pub migrate_clock: bool,
-    /// The byte string that identifies the device.
-    device_id: DeviceId,
 }
 
 qom_isa!(PL011State : SysBusDevice, DeviceState, Object);
 
+pub struct PL011Class {
+    parent_class: <SysBusDevice as ObjectType>::Class,
+    /// The byte string that identifies the device.
+    device_id: DeviceId,
+}
+
 unsafe impl ObjectType for PL011State {
-    type Class = <SysBusDevice as ObjectType>::Class;
+    type Class = PL011Class;
     const TYPE_NAME: &'static CStr = crate::TYPE_PL011;
 }
 
+impl ClassInitImpl<PL011Class> for PL011State {
+    fn class_init(klass: &mut PL011Class) {
+        klass.device_id = DeviceId::ARM;
+        <Self as ClassInitImpl<SysBusDeviceClass>>::class_init(&mut klass.parent_class);
+    }
+}
+
 impl ObjectImpl for PL011State {
     type ParentType = SysBusDevice;
 
@@ -214,7 +218,8 @@ impl PL011State {
 
         let value = match RegisterOffset::try_from(offset) {
             Err(v) if (0x3f8..0x400).contains(&(v >> 2)) => {
-                u32::from(self.device_id[(offset - 0xfe0) >> 2])
+                let device_id = self.get_class().device_id;
+                u32::from(device_id[(offset - 0xfe0) >> 2])
             }
             Err(_) => {
                 // qemu_log_mask(LOG_GUEST_ERROR, "pl011_read: Bad offset 0x%x\n", (int)offset);
@@ -648,16 +653,10 @@ pub struct PL011Luminary {
     parent_obj: ParentField<PL011State>,
 }
 
-impl PL011Luminary {
-    /// Initializes a pre-allocated, unitialized instance of `PL011Luminary`.
-    ///
-    /// # Safety
-    ///
-    /// We expect the FFI user of this function to pass a valid pointer, that
-    /// has the same size as [`PL011Luminary`]. We also expect the device is
-    /// readable/writeable from one thread at any time.
-    unsafe fn init(&mut self) {
-        self.parent_obj.device_id = DeviceId::Luminary;
+impl ClassInitImpl<PL011Class> for PL011Luminary {
+    fn class_init(klass: &mut PL011Class) {
+        klass.device_id = DeviceId::LUMINARY;
+        <Self as ClassInitImpl<SysBusDeviceClass>>::class_init(&mut klass.parent_class);
     }
 }
 
@@ -670,8 +669,6 @@ unsafe impl ObjectType for PL011Luminary {
 
 impl ObjectImpl for PL011Luminary {
     type ParentType = PL011State;
-
-    const INSTANCE_INIT: Option<unsafe fn(&mut Self)> = Some(Self::init);
 }
 
 impl DeviceImpl for PL011Luminary {}