Added code to support getting interrupts from the PIC. Can now get some data from the keyboard, however, it's not quite working yet.

2020-08-06 22:36:39 -05:00
parent db1a68188f
commit 49efafe173
15 changed files with 278 additions and 39 deletions
@@ -0,0 +1,58 @@
+#include "../includes/pic.h"
+#include "../includes/io.h"
+#include "../includes/idt.h"
+#include "../includes/irq.h"
+
+#define PIC1_PORT 				0x20
+#define PIC1_DATA_PORT			0X21
+#define PIC2_PORT 				0xA0
+#define PIC2_DATA_PORT			0XA1
+
+#define PIC1_START_INTERRUPT 	0x20
+#define PIC2_START_INTERRUPT 	0x28
+#define PIC2_END_INTERRUPT   	PIC2_START_INTERRUPT + 7
+
+#define PIC_ACK 				0x20
+
+void pic_acknowledge(unsigned int interrupt_no)
+{
+	if (interrupt_no < PIC2_START_INTERRUPT)
+		outb(PIC1_PORT, PIC_ACK);
+	else
+		outb(PIC2_PORT, PIC_ACK);
+}
+
+void setup_pics(void)
+{
+	// The PIC uses Initialization Command Words (ICW) to communicate.
+	// So we start with the first ICW, 0x11, this tells the PIC to expect 
+	// 3 more ICWs.
+	outb(PIC1_PORT, 0x11);
+	outb(PIC2_PORT, 0x11);
+	
+	// This tells the pic what offset to use when it generates the interrupt numbers.
+	// Since the first 32 ISRs are reserved by the CPU we must start at IRS32 and work
+	// our way up. When the PIC recieves an interrupt on it's input line, it will add
+	// the supplied values to that number before sending the newly made number to the CPU.
+	// Thereby remapping an interrupt number that would have normally conflicted with the 
+	// values in the IDT.
+	outb(PIC1_DATA_PORT, PIC1_START_INTERRUPT);
+	outb(PIC2_DATA_PORT, PIC2_START_INTERRUPT);
+	
+	// This ICW allows for cascading of their outputs to inputs between each other.
+	// I'm not sure what that really means but at this current time I'm not going to
+	// be doing this, so the bits will all be set to zero.
+	outb(PIC1_DATA_PORT, 0x00);
+	outb(PIC2_DATA_PORT, 0x00);
+	
+	// This is the environment info, and setting the lowest bit tells the PICs
+	// that we're running in 80x86 mode.
+	outb(PIC1_DATA_PORT, 0x01);
+	outb(PIC2_DATA_PORT, 0x01);
+	
+	// Finally, we have the interrupt masks.
+	outb(PIC1_DATA_PORT, 0xFF);
+	outb(PIC2_DATA_PORT, 0xFF);
+	
+	idt_set_gate(33, (unsigned long) &irq1, 0x08, 0x8E);
+}