From 95372a66e6278f723e20468b1625d3d2b5acd121 Mon Sep 17 00:00:00 2001
From: Gregory Bowne <gbowne144@gmail.com>
Date: Wed, 28 Jan 2026 10:47:35 -0800
Subject: [PATCH] Create pic.c

Implementation for pic.h
---
 pic.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 pic.c

diff --git a/pic.c b/pic.c
new file mode 100644
index 0000000..457ffe8
--- /dev/null
+++ b/pic.c
@@ -0,0 +1,76 @@
+#include "pic.h"
+#include "io.h"
+
+/* Small delay for older hardware bus timing */
+static inline void io_wait(void) {
+    outb(0x80, 0); 
+}
+
+void pic_init(void) {
+    uint8_t a1, a2;
+
+    // Save current masks
+    a1 = inb(PIC1_DATA);
+    a2 = inb(PIC2_DATA);
+
+    // ICW1: Start initialization in cascade mode
+    outb(PIC1_COMMAND, 0x11);
+    io_wait();
+    outb(PIC2_COMMAND, 0x11);
+    io_wait();
+
+    // ICW2: Master PIC vector offset
+    outb(PIC1_DATA, PIC1_OFFSET);
+    io_wait();
+    // ICW2: Slave PIC vector offset
+    outb(PIC2_DATA, PIC2_OFFSET);
+    io_wait();
+
+    // ICW3: Tell Master there is a slave at IRQ2 (0000 0100)
+    outb(PIC1_DATA, 4);
+    io_wait();
+    // ICW3: Tell Slave its cascade identity (0000 0010)
+    outb(PIC2_DATA, 2);
+    io_wait();
+
+    // ICW4: Set 8086/88 mode
+    outb(PIC1_DATA, 0x01);
+    io_wait();
+    outb(PIC2_DATA, 0x01);
+    io_wait();
+
+    // Restore masks (or disable all to start clean)
+    outb(PIC1_DATA, 0xFB); // Keep IRQ2 (cascade) open
+    outb(PIC2_DATA, 0xFF);
+}
+
+void pic_send_eoi(uint8_t irq) {
+    if (irq >= 8) {
+        outb(PIC2_COMMAND, PIC_EOI);
+    }
+    outb(PIC1_COMMAND, PIC_EOI);
+}
+
+void pic_unmask(uint8_t irq) {
+    uint16_t port;
+    if (irq < 8) {
+        port = PIC1_DATA;
+    } else {
+        port = PIC2_DATA;
+        irq -= 8;
+    }
+    uint8_t value = inb(port) & ~(1 << irq);
+    outb(port, value);
+}
+
+void pic_mask(uint8_t irq) {
+    uint16_t port;
+    if (irq < 8) {
+        port = PIC1_DATA;
+    } else {
+        port = PIC2_DATA;
+        irq -= 8;
+    }
+    uint8_t value = inb(port) | (1 << irq);
+    outb(port, value);
+}