From f6c3d349658720aa7488d6a40b85a965d3f29c5b Mon Sep 17 00:00:00 2001
From: Rajas Paranjpe <52586855+ChocolateLoverRaj@users.noreply.github.com>
Date: Sat, 19 Sep 2026 11:36:30 -0700
Subject: [PATCH] Add `set_interrupt_model_used` method for calling `\_PIC`

Tested on QEMU q35 and Lenovo Ideapad Z560.
---
 src/aml/interrupt_model_used.rs | 50 +++++++++++++++++++++++++++++++++
 src/aml/mod.rs                  |  2 ++
 src/aml/pci_routing.rs          |  4 +++
 3 files changed, 56 insertions(+)
 create mode 100644 src/aml/interrupt_model_used.rs

diff --git a/src/aml/interrupt_model_used.rs b/src/aml/interrupt_model_used.rs
new file mode 100644
index 00000000..f6f3f40a
--- /dev/null
+++ b/src/aml/interrupt_model_used.rs
@@ -0,0 +1,50 @@
+use alloc::vec;
+use core::str::FromStr;
+
+use crate::{
+    Handler,
+    aml::{
+        AmlError,
+        Interpreter,
+        namespace::AmlName,
+        object::{Object, WrappedObject},
+    },
+};
+
+/// See <https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html?highlight=_pic#pic-method>.
+#[non_exhaustive]
+#[derive(Debug, Clone, Copy)]
+pub enum InterruptModelUsed {
+    /// 0 - PIC mode
+    PicMode,
+    /// 1 - APIC mode
+    ApicMode,
+    /// 2 - SAPIC mode
+    SapicMode,
+}
+
+impl From<InterruptModelUsed> for Object {
+    fn from(value: InterruptModelUsed) -> Self {
+        Self::Integer(match value {
+            InterruptModelUsed::PicMode => 0,
+            InterruptModelUsed::ApicMode => 1,
+            InterruptModelUsed::SapicMode => 2,
+        })
+    }
+}
+
+impl<H> Interpreter<H>
+where
+    H: Handler,
+{
+    /// Calls the [`\_PIC` method](https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html?highlight=_pic#pic-method).
+    /// The method is optional, so if it doesn't exist this function returns success. Returns `true` is the method was called, `false` if it doesn't exist.
+    pub fn set_interrupt_model_used(&self, model: InterruptModelUsed) -> Result<bool, AmlError> {
+        Ok(self
+            .evaluate_if_present(
+                AmlName::from_str(r#"\_PIC"#).expect("valid name"),
+                vec![WrappedObject::new(model.into())],
+            )?
+            .is_some())
+    }
+}
diff --git a/src/aml/mod.rs b/src/aml/mod.rs
index 44ef3583..b3e5dcf3 100644
--- a/src/aml/mod.rs
+++ b/src/aml/mod.rs
@@ -16,6 +16,7 @@
  *  - Fuzzing and guarantee panic-free interpretation
  */
 
+mod interrupt_model_used;
 pub mod namespace;
 pub mod object;
 pub mod op_region;
@@ -47,6 +48,7 @@ use core::{
     str::FromStr,
     sync::atomic::{AtomicU64, Ordering},
 };
+pub use interrupt_model_used::InterruptModelUsed;
 use log::{error, info, trace, warn};
 use namespace::{AmlName, Namespace, NamespaceLevelKind};
 use object::{
diff --git a/src/aml/pci_routing.rs b/src/aml/pci_routing.rs
index 47df1b13..4cbb48aa 100644
--- a/src/aml/pci_routing.rs
+++ b/src/aml/pci_routing.rs
@@ -58,6 +58,10 @@ impl PciRoutingTable {
     /// `AmlError::InvalidOperationOnObject` if the value passed is not a package, or if any of the
     /// values within it are not packages. Returns the various `AmlError::Prt*` errors if the
     /// internal structure of the entries is invalid.
+    ///
+    /// Before calling this method, `\_PIC` should be called. See [`Interpreter::set_interrupt_model_used`].
+    /// The evaluation of `_PRT` can depend on the interrupt model being used. If `\_PIC` is not called,
+    /// the evaluation of PCI interrupts to GSI numbers can return incorrect results.
     pub fn from_prt_path(
         prt_path: AmlName,
         interpreter: &Interpreter<impl Handler>,