From c4845de1e4ba49ba066e5729814fdb5bcd7e46f8 Mon Sep 17 00:00:00 2001
From: Danny Holman <dholman@gymli.xyz>
Date: Tue, 28 Sep 2021 12:25:46 -0500
Subject: arch: i386: add PIC register support

Add functions that let the OS read the internal state registers of the
8259 PIC.

Signed-off-by: Danny Holman <dholman@gymli.xyz>
---
 arch/i386/boot/pic.c           | 14 ++++++++++++++
 arch/i386/include/kernel/pic.h |  5 +++++
 2 files changed, 19 insertions(+)

diff --git a/arch/i386/boot/pic.c b/arch/i386/boot/pic.c
index f103b92..607023c 100644
--- a/arch/i386/boot/pic.c
+++ b/arch/i386/boot/pic.c
@@ -22,6 +22,20 @@ void pic_remap(void) {
         outb(PIC2_DATA, a2);
 }
 
+static uint16_t __pic_get_irq_reg(int ocw3) {
+        outb(PIC1_COMMAND, ocw3);
+        outb(PIC2_COMMAND, ocw3);
+        return (inb(PIC2_COMMAND) << 8) | inb(PIC1_COMMAND);
+}
+
+uint16_t pic_get_irr(void) {
+        return __pic_get_irq_reg(PIC_READ_IRR);
+}
+
+uint16_t pic_get_isr(void) {
+        return __pic_get_irq_reg(PIC_READ_ISR);
+}
+
 void irq_set_mask(uint8_t irq) {
         uint16_t port;
         uint8_t data;
diff --git a/arch/i386/include/kernel/pic.h b/arch/i386/include/kernel/pic.h
index c3ede4f..a9387db 100644
--- a/arch/i386/include/kernel/pic.h
+++ b/arch/i386/include/kernel/pic.h
@@ -22,6 +22,9 @@
 #define ICW4_BUF_MASTER 0x0C
 #define ICW4_SFNM       0x10
 
+#define PIC_READ_IRR    0x0A
+#define PIC_READ_ISR    0x0B
+
 static inline void outb(uint16_t port, uint8_t value) {
         asm volatile("outb %0, %1" : : "a"(value), "Nd"(port));
 }
@@ -38,6 +41,8 @@ static inline void io_wait(void) {
 
 void pic_eoi(unsigned char irq);
 void pic_remap(void);
+uint16_t pic_get_irr(void);
+uint16_t pic_get_isr(void);
 
 void irq_set_mask(uint8_t irq);
 void irq_clear_mask(uint8_t irq);
-- 
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