[PATCH 04/14] hw/core: Introduce TYPE_SHARED_IRQ

[Bernhard Beschow]

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
---
 include/hw/core/shared-irq.h | 39 ++++++++++++++++
 hw/core/shared-irq.c         | 88 ++++++++++++++++++++++++++++++++++++
 hw/core/Kconfig              |  3 ++
 hw/core/meson.build          |  1 +
 4 files changed, 131 insertions(+)
 create mode 100644 include/hw/core/shared-irq.h
 create mode 100644 hw/core/shared-irq.c

diff --git a/include/hw/core/shared-irq.h b/include/hw/core/shared-irq.h
new file mode 100644
index 0000000000..803c303dd0
--- /dev/null
+++ b/include/hw/core/shared-irq.h
@@ -0,0 +1,39 @@
+/*
+ * IRQ sharing device.
+ *
+ * Copyright (c) 2025 Bernhard Beschow <shentey@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+/*
+ * This is a simple device which has one GPIO output line and multiple GPIO
+ * input lines. The output line is active if at least one of the input lines 
is.
+ *
+ * QEMU interface:
+ *  + N unnamed GPIO inputs: the input lines
+ *  + one unnamed GPIO output: the output line
+ *  + QOM property "num-lines": sets the number of input lines
+ */
+#ifndef HW_SHARED_IRQ_H
+#define HW_SHARED_IRQ_H
+
+#include "hw/sysbus.h"
+#include "qom/object.h"
+
+#define TYPE_SHARED_IRQ "shared-irq"
+
+#define MAX_SHARED_LINES 16
+
+
+OBJECT_DECLARE_SIMPLE_TYPE(SharedIRQ, SHARED_IRQ)
+
+struct SharedIRQ {
+    DeviceState parent_obj;
+
+    qemu_irq out_irq;
+    uint16_t irq_states;
+    uint8_t num_lines;
+};
+
+#endif
diff --git a/hw/core/shared-irq.c b/hw/core/shared-irq.c
new file mode 100644
index 0000000000..b2a4ea4a66
--- /dev/null
+++ b/hw/core/shared-irq.c
@@ -0,0 +1,88 @@
+/*
+ * IRQ sharing device.
+ *
+ * Copyright (c) 2025 Bernhard Beschow <shentey@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "hw/core/shared-irq.h"
+#include "hw/irq.h"
+#include "hw/qdev-properties.h"
+#include "qapi/error.h"
+#include "migration/vmstate.h"
+
+static void shared_irq_handler(void *opaque, int n, int level)
+{
+    SharedIRQ *s = opaque;
+    uint16_t mask = BIT(n);
+
+    if (level) {
+        s->irq_states |= mask;
+    } else {
+        s->irq_states &= ~mask;
+    }
+
+    qemu_set_irq(s->out_irq, !!s->irq_states);
+}
+
+static void shared_irq_init(Object *obj)
+{
+    SharedIRQ *s = SHARED_IRQ(obj);
+
+    qdev_init_gpio_out(DEVICE(s), &s->out_irq, 1);
+}
+
+static void shared_irq_realize(DeviceState *dev, Error **errp)
+{
+    SharedIRQ *s = SHARED_IRQ(dev);
+
+    if (s->num_lines < 1 || s->num_lines >= MAX_SHARED_LINES) {
+        error_setg(errp,
+                   "IRQ shared number of lines %d must be between 1 and %d",
+                   s->num_lines, MAX_SHARED_LINES);
+        return;
+    }
+
+    qdev_init_gpio_in(dev, shared_irq_handler, s->num_lines);
+}
+
+static const Property shared_irq_properties[] = {
+    DEFINE_PROP_UINT8("num-lines", SharedIRQ, num_lines, 1),
+};
+
+static const VMStateDescription shared_irq_vmstate = {
+    .name = TYPE_SHARED_IRQ,
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT16(irq_states, SharedIRQ),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
+static void shared_irq_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    /* No state to reset */
+    device_class_set_props(dc, shared_irq_properties);
+    dc->vmsd = &shared_irq_vmstate;
+    dc->realize = shared_irq_realize;
+
+    /* Reason: Needs to be wired up to work */
+    dc->user_creatable = false;
+}
+
+static const TypeInfo shared_irq_types[] = {
+    {
+       .name = TYPE_SHARED_IRQ,
+       .parent = TYPE_DEVICE,
+       .instance_size = sizeof(SharedIRQ),
+       .instance_init = shared_irq_init,
+       .class_init = shared_irq_class_init,
+    },
+};
+
+DEFINE_TYPES(shared_irq_types)
diff --git a/hw/core/Kconfig b/hw/core/Kconfig
index d1bdf765ee..ddff977963 100644
--- a/hw/core/Kconfig
+++ b/hw/core/Kconfig
@@ -32,6 +32,9 @@ config PLATFORM_BUS
 config REGISTER
     bool
 
+config SHARED_IRQ
+    bool
+
 config SPLIT_IRQ
     bool
 
diff --git a/hw/core/meson.build b/hw/core/meson.build
index ce9dfa3f4b..6b5bdc8ec7 100644
--- a/hw/core/meson.build
+++ b/hw/core/meson.build
@@ -21,6 +21,7 @@ system_ss.add(when: 'CONFIG_OR_IRQ', if_true: 
files('or-irq.c'))
 system_ss.add(when: 'CONFIG_PLATFORM_BUS', if_true: files('platform-bus.c'))
 system_ss.add(when: 'CONFIG_PTIMER', if_true: files('ptimer.c'))
 system_ss.add(when: 'CONFIG_REGISTER', if_true: files('register.c'))
+system_ss.add(when: 'CONFIG_SHARED_IRQ', if_true: files('shared-irq.c'))
 system_ss.add(when: 'CONFIG_SPLIT_IRQ', if_true: files('split-irq.c'))
 system_ss.add(when: 'CONFIG_XILINX_AXI', if_true: files('stream.c'))
 system_ss.add(when: 'CONFIG_PLATFORM_BUS', if_true: files('sysbus-fdt.c'))
-- 
2.47.1