The existing aml_interrupt() uses the Extended Interrupt Descriptor to store
the interrupt information, however newer Windows will only parse the
standard IRQ Descriptor when enumerating ISA serial ports.

Signed-off-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
---
 include/hw/acpi/aml-build.h |  2 ++
 hw/acpi/aml-build-stub.c    |  6 ++++++
 hw/acpi/aml-build.c         | 25 +++++++++++++++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/include/hw/acpi/aml-build.h b/include/hw/acpi/aml-build.h
index f38e129719..3394253b9e 100644
--- a/include/hw/acpi/aml-build.h
+++ b/include/hw/acpi/aml-build.h
@@ -342,6 +342,8 @@ Aml *aml_io(AmlIODecode dec, uint16_t min_base, uint16_t max_base,
 Aml *aml_operation_region(const char *name, AmlRegionSpace rs,
                           Aml *offset, uint32_t len);
 Aml *aml_irq_no_flags(uint8_t irq);
+Aml *aml_irq(uint8_t irq, AmlLevelAndEdge level_and_edge,
+             AmlActiveHighAndLow high_and_low, AmlShared shared);
 Aml *aml_named_field(const char *name, unsigned length);
 Aml *aml_reserved_field(unsigned length);
 Aml *aml_local(int num);
diff --git a/hw/acpi/aml-build-stub.c b/hw/acpi/aml-build-stub.c
index 89a8fec4af..3180c7c962 100644
--- a/hw/acpi/aml-build-stub.c
+++ b/hw/acpi/aml-build-stub.c
@@ -67,6 +67,12 @@ Aml *aml_irq_no_flags(uint8_t irq)
     return NULL;
 }
 
+Aml *aml_irq(uint8_t irq, AmlLevelAndEdge level_and_edge,
+             AmlActiveHighAndLow high_and_low, AmlShared shared)
+{
+    return NULL;
+}
+
 Aml *aml_interrupt(AmlConsumerAndProducer con_and_pro,
                    AmlLevelAndEdge level_and_edge,
                    AmlActiveHighAndLow high_and_low, AmlShared shared,
diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
index ea1c415b21..b07b0133c2 100644
--- a/hw/acpi/aml-build.c
+++ b/hw/acpi/aml-build.c
@@ -1058,6 +1058,31 @@ Aml *aml_irq_no_flags(uint8_t irq)
     return var;
 }
 
+/*
+ * ACPI 1.0b: 6.4.2.1.1 ASL Macro for IRQ Descriptor
+ *
+ * More verbose description at:
+ * ACPI 5.0: 19.5.63 IRQ (Interrupt Resource Descriptor Macro)
+ *           6.4.2.1 IRQ Descriptor
+ */
+Aml *aml_irq(uint8_t irq, AmlLevelAndEdge level_and_edge,
+             AmlActiveHighAndLow high_and_low, AmlShared shared)
+{
+    uint16_t irq_mask;
+    Aml *var = aml_alloc();
+    uint8_t irq_flags = level_and_edge | (high_and_low << 3) |
+                        (shared << 4);
+
+    assert(irq < 16);
+    build_append_byte(var->buf, 0x23); /* IRQ descriptor 3 byte form */
+
+    irq_mask = 1U << irq;
+    build_append_byte(var->buf, irq_mask & 0xFF); /* IRQ mask bits[7:0] */
+    build_append_byte(var->buf, irq_mask >> 8); /* IRQ mask bits[15:8] */
+    build_append_byte(var->buf, irq_flags); /* IRQ flags */
+    return var;
+}
+
 /* ACPI 1.0b: 16.2.5.4 Type 2 Opcodes Encoding: DefLNot */
 Aml *aml_lnot(Aml *arg)
 {
-- 
2.43.0