Added timer module

kernel/include/kernel/timer.h

@@ -0,0 +1,16 @@
+#ifndef TIMER_H_
+#define TIMER_H_
+
+#include <stdint.h>
+
+/*
+ * timer_init:
+ *  Initializes the timer to a give tick frequency.
+ *
+ * @param freq - Frequency
+ *
+ */
+
+void timer_init(uint32_t freq);
+
+#endif

kernel/timer/include/timer_internals.h

@@ -0,0 +1,22 @@
+#ifndef TIMER_INTERNALS_H_
+#define TIMER_INTERNALS_H_
+
+/* Command ports. */
+
+#define PIT_COMMAND_PORT 0x43
+
+/* Data ports. */
+
+#define PIT_CH0_DATA_PORT 0x40
+#define PIT_CH1_DATA_PORT 0x41
+#define PIT_CH2_DATA_PORT 0x42
+
+/* Command bytes. */
+
+#define PIT_DIV_READY 0x36
+
+/* Default frequency of PIT's internal clock. */
+
+#define PIT_DEFAULT_FREQ 1193180
+
+#endif

kernel/timer/src/timer.c

@@ -0,0 +1,51 @@
+#include "kernel/timer.h"
+
+#include "timer_internals.h"
+
+#include "kernel/screen.h"
+
+#include "i386/irq.h"
+
+#include "lib/memio.h"
+
+#include <stdio.h>
+
+static uint32_t tick;
+
+/*
+ * timer_intrpt_handler:
+ * ---------------------
+ *
+ */
+
+static void timer_intrpt_handler(__attribute__ ((unused)) context_t ctx) {
+
+    tick++;
+    screen_delete_line();
+    printf("Tick: %d", tick);
+
+}
+
+/*
+ * timer_init:
+ * -----------
+ *
+ *  Register the IRQ and sent the frequency to PIT.
+ *
+ */
+
+void timer_init(uint32_t freq) {
+
+    register_irq(IRQ0, timer_intrpt_handler);
+
+    outb(PIT_COMMAND_PORT, PIT_DIV_READY);
+
+    uint16_t divisor = PIT_DEFAULT_FREQ / freq;
+
+    uint8_t freq_low  = (uint8_t) (divisor & 0xFF);
+    uint8_t freq_high = (uint8_t) (divisor >> 8);
+
+    outb(PIT_CH0_DATA_PORT, freq_low);
+    outb(PIT_CH0_DATA_PORT, freq_high);
+
+}