add PIT

src/isr.c

@@ -3,6 +3,7 @@
 #include "../include/types.h"
 #include "../include/screen.h"
 #include "../include/pic.h"
+#include "../include/pit.h"
 
 typedef size_t uword_t;
 struct interrupt_frame
@@ -14,6 +15,7 @@ struct interrupt_frame
     uword_t ss;
 };
 
+__attribute__((interrupt)) void isr_timer(struct interrupt_frame *frame);
 void isr_custom();
 void default_handler();
 
@@ -54,6 +56,7 @@ void isr_install() {
     for(int i = 32; i < 255; i++)
 	idt_set_descriptor(i, (uint32)default_handler, 0x8E);
 
+    idt_set_descriptor(0x20, (uint32)isr_timer, 0x8E);
     idt_set_descriptor(0x21, (uint32)isr_custom, 0x8E);
 
 
@@ -66,6 +69,12 @@ void default_handler()
 
 }
 
+__attribute__((interrupt)) void isr_timer(struct interrupt_frame *frame)
+{
+	pit_init();
+	pic_end_int(0x0);
+}
+
 void handle_keyboard()
 {
 	uint8_t scancode = inb(0x60);
@@ -76,7 +85,7 @@ __attribute__((interrupt)) void isr_custom(struct interrupt_frame *frame)
 {
 	//terminal_writestring("YOOOOO!!!!!! I LOVE KATYA!!!!");
 	handle_keyboard();
-	pic_end_int(0x21);
+	pic_end_int(0x1);
 }
 
 void isr0()

src/kernel.c

@@ -5,6 +5,7 @@
 #include "../include/disk.h"
 #include "../include/string.h"
 #include "../include/pic.h"
+#include "../include/pit.h"
 
 #include <stdint.h>
 
@@ -14,8 +15,9 @@ void kmain()
 	printf("KatauOS booting up\n");
 	isr_install();
 	pic_remap(0x20, 0x28);
+	pit_init();
 	//only enable keyboard IRQs
-	outb(0x21,0xfd);
+	outb(0x21,0xfc);
    	outb(0xa1,0xff);
 
 	printf("Kernel init sequence completed\n");

src/pit.c

@@ -0,0 +1,37 @@
+#include "../include/pit.h"
+
+//https://wiki.osdev.org/Programmable_Interval_Timer
+
+/*
+Bit/s        Usage
+7            Output pin state
+6            Null count flags
+5 and 4      Access mode :
+                0 0 = Latch count value command
+                0 1 = Access mode: lobyte only
+                1 0 = Access mode: hibyte only
+                1 1 = Access mode: lobyte/hibyte
+3 to 1       Operating mode :
+                0 0 0 = Mode 0 (interrupt on terminal count)
+                0 0 1 = Mode 1 (hardware re-triggerable one-shot)
+                0 1 0 = Mode 2 (rate generator)
+                0 1 1 = Mode 3 (square wave generator)
+                1 0 0 = Mode 4 (software triggered strobe)
+                1 0 1 = Mode 5 (hardware triggered strobe)
+                1 1 0 = Mode 2 (rate generator, same as 010b)
+                1 1 1 = Mode 3 (square wave generator, same as 011b)
+0            BCD/Binary mode: 0 = 16-bit binary, 1 = four-digit BCD
+*/
+
+#define PIT_COMMAND_PORT 0x43
+#define PIT_DATA_PORT 0x40
+
+void pit_init() {
+    uint16_t frequency = 100;
+    uint8_t command = 0x36;//00110110 see above to get the idea wtf is this number
+
+    outb(PIT_COMMAND_PORT, command);
+
+    outb(PIT_DATA_PORT, (uint8_t)(frequency & 0xFF));
+    outb(PIT_DATA_PORT, (uint8_t)((frequency >> 8) & 0xFF));
+}