From 97598b96dbf756bc29215fd7e31671cd1acfb08f Mon Sep 17 00:00:00 2001
From: Ruslan Isaev <ubijca16@gmail.com>
Date: Wed, 19 Mar 2025 13:10:41 +0300
Subject: [PATCH] add PIC code from osdev

---
 Makefile      |  5 +++-
 include/pic.h |  8 ++++++
 src/kernel.c  |  2 ++
 src/pic.c     | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 86 insertions(+), 1 deletion(-)
 create mode 100644 include/pic.h
 create mode 100644 src/pic.c

diff --git a/Makefile b/Makefile
index 8d6ad9d..a429b21 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 # Define the object files
-OBJS = bin/boot.o bin/kernel.o bin/idt.o bin/isr.o bin/screen.o bin/utils.o bin/string.o bin/stdio.o bin/disk.o
+OBJS = bin/boot.o bin/kernel.o bin/idt.o bin/isr.o bin/screen.o bin/utils.o bin/string.o bin/stdio.o bin/disk.o bin/pic.o
 
 # Define the compiler and assembler
 CC = gcc -D__is_katauos
@@ -58,6 +58,9 @@ bin/stdio.o: src/stdio.c
 bin/disk.o: src/disk.c
 	$(CC) $(CFLAGS) -c $< -o $@
 
+bin/pic.o: src/pic.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
 clean:
 	rm -rf bin/
 	rm -f $(OUTPUT)
diff --git a/include/pic.h b/include/pic.h
new file mode 100644
index 0000000..aa06fcd
--- /dev/null
+++ b/include/pic.h
@@ -0,0 +1,8 @@
+#ifndef PIC_H
+#define PIC_H
+
+#include "../include/utils.h"
+
+void pic_remap(int offset1, int offset2);
+
+#endif
diff --git a/src/kernel.c b/src/kernel.c
index 5da1a85..7f4c34a 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -4,6 +4,7 @@
 #include "../include/utils.h"
 #include "../include/disk.h"
 #include "../include/string.h"
+#include "../include/pic.h"
 
 #include <stdint.h>
 
@@ -11,6 +12,7 @@ void kmain()
 {
 	terminal_initialize();
 	printf("KatauOS booting up\n");
+	pic_remap(0x20, 0x28);
 	isr_install();
 	printf("Kernel init sequence completed\n");
 
diff --git a/src/pic.c b/src/pic.c
new file mode 100644
index 0000000..5c7495b
--- /dev/null
+++ b/src/pic.c
@@ -0,0 +1,72 @@
+#include "../include/pic.h"
+
+//took this straight outta https://wiki.osdev.org/8259_PIC#Code_Examples
+
+#define PIC1		0x20		/* IO base address for master PIC */
+#define PIC2		0xA0		/* IO base address for slave PIC */
+#define PIC1_COMMAND	PIC1
+#define PIC1_DATA	(PIC1+1)
+#define PIC2_COMMAND	PIC2
+#define PIC2_DATA	(PIC2+1)
+
+#define PIC_EOI		0x20		/* End-of-interrupt command code */
+
+#define PIC_READ_IRR                0x0a    /* OCW3 irq ready next CMD read */
+#define PIC_READ_ISR                0x0b    /* OCW3 irq service next CMD read */
+
+/* reinitialize the PIC controllers, giving them specified vector offsets
+   rather than 8h and 70h, as configured by default */
+
+#define ICW1_ICW4	0x01		/* Indicates that ICW4 will be present */
+#define ICW1_SINGLE	0x02		/* Single (cascade) mode */
+#define ICW1_INTERVAL4	0x04		/* Call address interval 4 (8) */
+#define ICW1_LEVEL	0x08		/* Level triggered (edge) mode */
+#define ICW1_INIT	0x10		/* Initialization - required! */
+
+#define ICW4_8086	0x01		/* 8086/88 (MCS-80/85) mode */
+#define ICW4_AUTO	0x02		/* Auto (normal) EOI */
+#define ICW4_BUF_SLAVE	0x08		/* Buffered mode/slave */
+#define ICW4_BUF_MASTER	0x0C		/* Buffered mode/master */
+#define ICW4_SFNM	0x10		/* Special fully nested (not) */
+
+static inline void io_wait()
+{
+        outb(0x80, 0x00);
+}
+
+
+/*
+arguments:
+	offset1 - vector offset for master PIC
+		vectors on the master become offset1..offset1+7
+	offset2 - same for slave PIC: offset2..offset2+7
+*/
+void pic_remap(int offset1, int offset2)
+{
+	outb(PIC1_COMMAND, ICW1_INIT | ICW1_ICW4);  // starts the initialization sequence (in cascade mode)
+	io_wait();
+	outb(PIC2_COMMAND, ICW1_INIT | ICW1_ICW4);
+	io_wait();
+	outb(PIC1_DATA, offset1);                 // ICW2: Master PIC vector offset
+	io_wait();
+	outb(PIC2_DATA, offset2);                 // ICW2: Slave PIC vector offset
+	io_wait();
+	outb(PIC1_DATA, 4);                       // ICW3: tell Master PIC that there is a slave PIC at IRQ2 (0000 0100)
+	io_wait();
+	outb(PIC2_DATA, 2);                       // ICW3: tell Slave PIC its cascade identity (0000 0010)
+	io_wait();
+
+	outb(PIC1_DATA, ICW4_8086);               // ICW4: have the PICs use 8086 mode (and not 8080 mode)
+	io_wait();
+	outb(PIC2_DATA, ICW4_8086);
+	io_wait();
+
+	// Unmask both PICs.
+	outb(PIC1_DATA, 0);
+	outb(PIC2_DATA, 0);
+}
+
+void pic_disable(void) {
+    outb(PIC1_DATA, 0xff);
+    outb(PIC2_DATA, 0xff);
+}