implements the PIT

kernel/arch/idt/idt.c

@@ -6,6 +6,7 @@
 #include <kernel/_kernel.h>
 #include <kernel/x86/idt.h>
 #include <kernel/x86/pic.h>
+#include <kernel/x86/pit.h>
 #include <kernel/x86/io.h>
 #include <kernel/x86/keyb.h>
 
@@ -16,8 +17,7 @@ static idtr_t idtr;
 
 static bool vectors[IDT_MAX_DESCRIPTORS];
 
-extern struct keyboard_state keyb_state;
-
+extern struct pit_state pit;
 
 #define EXTERNAL_BIT (0x1)
 
@@ -229,6 +229,10 @@ void exception_handler(struct cpu_state __attribute__((unused)) cpu, uint32_t in
 		/** EXCEPTIONS END **/
 
 		/** PIC BEGIN **/
+		case PIC_PIT:
+			pit.interrupts++;
+			PIC_sendEOI(0);
+			break;
 		case PIC_KEYB:
 			inbyte = inb(0x60);
 			do_keypress(decode_scancode(inbyte));
@@ -276,6 +280,7 @@ void idt_init(void)
 						  
 	PIC_remap(0x20, 0x28);
 	pic_disable(); // mask everything
+	IRQ_clear_mask(0);
 	IRQ_clear_mask(1);
 	
 	__asm__ volatile("sti"); // set the interrupt flag

kernel/arch/io/pit.c

@@ -61,4 +61,15 @@ void set_pit_count(uint8_t channel, uint16_t count) // Only in lobyte/hibyte mod
 	// TODO: make sure to set interrupts
 }
 
+void init_pit(uint8_t init_command, uint8_t channel, uint32_t divisor)
+{
+	uint32_t normalized_div = normalize_divisor(divisor);
 
+	pit.divisor = normalized_div;
+	pit.interrupts = 0;
+
+	outb(PIT_CMD_REG, init_command); // access mode must be lobyte/hibyte
+	
+	outb(channel, normalized_div & 0xFF);
+	outb(channel, (normalized_div & 0xFF00) >> 8);
+}

kernel/include/kernel/x86/pit.h

@@ -16,7 +16,7 @@
  */
 enum PIT_CHANNEL {
 	CHANNEL_0 = 0x0,
-	CHANNEL_1,
+	CHANNEL_1, // this channel isn't always here...
 	CHANNEL_2,
 	/**
 	 * Isn't supported on 8253 chips, but should be supported on AT and later (except for PS/2).
@@ -245,9 +245,12 @@ enum PIT_DIGIT_MODE {
 
 struct pit_state {
 	uint32_t divisor;
+	// this allows us to track a.. very long time before an overflow... 52ms * INT64MAX = 4.8e20ms = 5.6e12 days = 1.5e7 centuries 
+	// TODO: ... handle overflow? :p
+	uint64_t interrupts; 
 } __attribute__((packed));
 
-void init_pit(uint32_t divisor);
+void init_pit(uint8_t init_command, uint8_t channel, uint32_t divisor);
 
 double get_time_from_divisor(uint32_t divisor);
 

kernel/kmain.c

@@ -8,6 +8,7 @@
 #include <kernel/x86/idt.h>
 #include <kernel/x86/io.h>
 #include <kernel/x86/keyb.h>
+#include <kernel/x86/pit.h>
 
 #include <kernel/x86/pit.h>
 
@@ -28,6 +29,8 @@ void kmain(void)
 	
 	init_kb();
 
+	init_pit(0x36, PIT_CHANNEL_0, 0);
+
 	printf("%f\n", get_time_from_divisor(10));
 
 	printf("Entering loop...\n");