1 files changed, 63 insertions, 0 deletions
diff --git a/src/pic.cpp b/src/pic.cpp
new file mode 100644
index 0000000..437f384
--- /dev/null
+++ b/src/pic.cpp
@@ -0,0 +1,63 @@
+#include "pic.hpp"
+
+#include "portio.hpp"
+
+#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 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) */
+
+void pic_initialize()
+{
+    constexpr int offset1 = 0x20, offset2 = 0x28;
+    std::uint8_t a1, a2;
+    
+    a1 = inb(PIC1_DATA);                        // save masks
+    a2 = inb(PIC2_DATA);
+    
+    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();
+    
+    outb(PIC1_DATA, a1);   // restore saved masks.
+    outb(PIC2_DATA, a2);
+}
+
+void pic_eoi(std::uint8_t irq)
+{
+    if (irq >= 8)
+        outb(PIC2_COMMAND, PIC_EOI);
+
+    outb(PIC1_COMMAND, PIC_EOI);
+}
+