1 files changed, 92 insertions, 0 deletions
diff --git a/stage3/pic.c b/stage3/pic.c
new file mode 100644
index 0000000..726a6da
--- /dev/null
+++ b/stage3/pic.c
@@ -0,0 +1,92 @@
+#include "pic.h"
+#include "io.h"
+
+void disable_irqs()
+{
+	asm volatile("cli");
+}
+
+void enable_irqs()
+{
+	asm volatile("sti");
+}
+
+void ack_irq(u8 lane)
+{
+	if (lane >= 8)
+		outb(IO_PIC2_CTRL, 1 << 5);
+
+	outb(IO_PIC1_CTRL, 1 << 5);
+}
+
+void unmask_irq(u8 lane)
+{
+	u8 port = IO_PIC1_DATA;
+
+	if (lane >= 8) {
+		port = IO_PIC2_DATA;
+		lane -= 8;
+	}
+
+	outb(port, inb(port) & ~(1 << lane));
+}
+
+void pic_init()
+{
+	typedef struct {
+		bool ic4 : 1;
+		bool single : 1;
+		bool addr_interval : 1;
+		bool level_triggered : 1;
+		bool init : 1;
+		unsigned int zeros : 3;
+	} __attribute__((packed)) pic_icw1;
+
+	u8 icw1 = BITCAST(((pic_icw1) {
+		.ic4 = true,
+		.single = false,
+		.addr_interval = false,
+		.level_triggered = false,
+		.init = true,
+		.zeros = 0,
+	}), pic_icw1, u8);
+
+	outb(IO_PIC1_CTRL, icw1);
+	outb(IO_PIC2_CTRL, icw1);
+
+	// map IRQs 0-15 to 0x20-0x2F
+	// 0x1F is the highest reserved interrupt
+	outb(IO_PIC1_DATA, 0x20);
+	outb(IO_PIC2_DATA, 0x28);
+
+	// pic2 is connected to IRQ2
+	outb(IO_PIC1_DATA, 1 << 2);
+	outb(IO_PIC2_DATA, 2);
+
+	typedef struct {
+		bool x86 : 1;
+		bool auto_eoi : 1;
+		bool primary_buffered : 1;
+		bool buffered : 1;
+		bool fully_nested : 1;
+		unsigned int zeros : 3;
+	} __attribute__((packed)) pic_icw4;
+
+	u8 icw4 = BITCAST(((pic_icw4) {
+		.x86 = true,
+		.auto_eoi = false,
+		.primary_buffered = false,
+		.buffered = false,
+		.fully_nested = false,
+		.zeros = 0,
+	}), pic_icw4, u8);
+
+	outb(IO_PIC1_DATA, icw4);
+	outb(IO_PIC2_DATA, icw4);
+
+	// mask all interrupts
+	outb(IO_PIC1_DATA, 0xff);
+	outb(IO_PIC2_DATA, 0xff);
+
+	disable_irqs();
+}