On 13/10/2026 17:17, Peter Maydell wrote:
On Wed, 16 Sept 2026 at 11:50, Mark Cave-Ayland
<[email protected]> wrote:
This device represents a PIC for an x86 machine consisting of 2 cascaded i8259
devices wired accordingly.
Signed-off-by: Mark Cave-Ayland <[email protected]>
---
hw/intc/i8259.c | 133 ++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 118 insertions(+), 15 deletions(-)
diff --git a/hw/intc/i8259.c b/hw/intc/i8259.c
index af33b71591..fcc94e12f8 100644
--- a/hw/intc/i8259.c
+++ b/hw/intc/i8259.c
@@ -25,7 +25,9 @@
#include "qemu/osdep.h"
#include "hw/intc/i8259.h"
#include "hw/core/irq.h"
+#include "hw/core/qdev-properties.h"
#include "hw/isa/isa.h"
+#include "qapi/error.h"
#include "qemu/timer.h"
#include "qemu/log.h"
#include "hw/isa/i8259_internal.h"
@@ -36,6 +38,22 @@
#define TYPE_I8259 "isa-i8259"
+#define TYPE_I8259_PIC "isa-i8259-pic"
+
+struct I8259PICState {
+ DeviceState parent_obj;
+
+ qemu_irq pic_out_irq;
+ qemu_irq pass_irqs[ISA_NUM_IRQS];
+
+ ISABus *isabus;
+ IRQState i8259_primary_out_irq;
+ I8259CommonState i8259[2];
This allocates only enough space for the common base class's
instance struct, but later we do an object_initialize_child()
of the child class. If the child class's state struct is
ever bigger than the common class, this will break.
That's true. In theory this should be something like I8259State, however
I didn't think it was worth adding a specific
OBJECT_DECLARE_SIMPLE_TYPE() if there were no extra fields. I did
quickly check that if this happens, then the assert() in
object_initialize() fires so if this did happen then we'd find out
really quickly.
static const TypeInfo i8259_type_infos[] = {
{
.name = TYPE_I8259,
.parent = TYPE_I8259_COMMON,
.class_init = i8259_class_init,
},
+ {
+ .name = TYPE_I8259_PIC,
+ .parent = TYPE_DEVICE,
Devices that directly inherit from TYPE_DEVICE are awkward,
because they never get reset. Conviently this device doesn't
currently need a reset method, but still, is this a good idea?
In this case I think it's correct, because the PIC device in this case
is a container for 2 cascaded i8259s which are connected separately to
the ISA bus. Therefore each i8259 will have its reset triggered via a
reset of the ISA bus.
The container itself can't exist on the ISA bus because it would then
appear as a separate device which doesn't make sense in this case.
+ .class_init = i8259_pic_class_init,
+ .instance_init = i8259_pic_init,
+ .instance_size = sizeof(I8259PICState),
+ },
};
DEFINE_TYPES(i8259_type_infos)
-- PMM
ATB,
Mark.
