Handout

kernel/arch/pic.cc

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+#include "pic.h"
+
+#include "ioport.h"
+
+namespace PIC {
+
+void initialize() {
+	// Access primary & secondary PIC via two ports each
+	IOPort primary_port_a(0x20);
+	IOPort primary_port_b(0x21);
+	IOPort secondary_port_a(0xa0);
+	IOPort secondary_port_b(0xa1);
+
+	// Initialization Command Word 1 (ICW1)
+	// Basic PIC configuration, starting initialization
+	enum InitializationCommandWord1 {
+		ICW4_NEEDED = 1 << 0,  // use Initialization Command Word 4
+		SINGLE_MODE = 1 << 1,  // Single or multiple (cascade mode)  8259A
+		ADDRESS_INTERVAL_HALF =
+			1
+			<< 2,  // 4 or 8 bit interval between the interrupt vector locations
+		LEVEL_TRIGGERED = 1 << 3,  // Level or edge triggered
+		ALWAYS_1 = 1 << 4,
+	};
+	const uint8_t icw1 = InitializationCommandWord1::ICW4_NEEDED |
+						 InitializationCommandWord1::ALWAYS_1;
+	// ICW1 in port A (each)
+	primary_port_a.outb(icw1);
+	secondary_port_a.outb(icw1);
+
+	// Initialization Command Word 2 (ICW2):
+	// Configure interrupt vector base offset in port B
+	primary_port_b.outb(0x20);	  // Primary: IRQ Offset 32
+	secondary_port_b.outb(0x28);  // Secondary: IRQ Offset 40
+
+	// Initialization Command Word 3 (ICW3):
+	// Configure pin on primary PIC connected to secondary PIC
+	const uint8_t pin = 2;			// Secondary connected on primary pin 2
+	primary_port_b.outb(1 << pin);	// Pin as bit mask for primary
+	secondary_port_b.outb(pin);		// Pin as value (ID) for secondary
+
+	// Initialization Command Word 4 (ICW4)
+	// Basic PIC configuration, starting initialization
+	enum InitializationCommandWord4 {
+		MODE_8086 = 1 << 0,		  // 8086/8088 or 8085 mode
+		AUTO_EOI = 1 << 1,		  // Single or multiple (cascade mode)  8259A
+		BUFFER_PRIMARY = 1 << 2,  // Primary or secondary buffering
+		BUFFERED_MODE = 1 << 3,	  // Enable or disable buffering (for primary or
+								  // secondary above)
+		SPECIAL_FULLY_NESTED = 1 << 4  // Special or non special fully nested
+	};
+	const uint8_t icw4 = InitializationCommandWord4::MODE_8086 |
+						 InitializationCommandWord4::AUTO_EOI;
+	// ICW3 in port B (each)
+	primary_port_b.outb(icw4);
+	secondary_port_b.outb(icw4);
+
+	// Operation Control Word 1 (OCW1):
+	// Disable (mask) all hardware interrupts on both legacy PICs (we'll use
+	// APIC)
+	secondary_port_b.outb(0xff);
+	primary_port_b.outb(0xff);
+}
+
+}  // namespace PIC