Incomplete screen driver.

drivers/screen.c

@@ -0,0 +1,46 @@
+#include "screen.h"
+
+#include "../kernel/ports.h"
+
+void print_char(char c, int col, int row, char attr_byte) {
+	unsigned char *vidmem = (unsigned char*) VIDEO_ADDRESS;
+
+	if(!attr_byte)
+		attr_byte = WHITE_ON_BLACK;
+
+	/* get the offset of the screen location specified */
+	int offset;
+	/*
+	 * if row & col are non-negative then they can be used
+	 * as an offset
+	 */
+	if(col >= 0 && row >= 0)
+	{
+		offset = get_screen_offset(col, row);
+	}
+	/* otherwise use the cursor's current location */
+	else
+	{
+		offset = get_cursor();
+	}
+
+	/* handle a newline */
+	if(c == '\n')
+	{
+		int rows = offset / (2 * MAX_COLS);
+		offset = get_screen_offset(79,rows);
+	}
+	/* else set the character */
+	else
+	{
+		vidmem[offset] = c;
+		vidmem[offset+1] = attr_byte;
+	}
+
+	/* update the offset to the next cell */
+	offset += 2;
+	/* set scrolling adjustment */
+	offset = handle_scrolling(offset);
+	/* update the cursor position */
+	set_cursor(offset);
+}

drivers/screen.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#define VIDEO_ADDRESS   0xb8000
+#define MAX_ROWS        25
+#define MAX_COLS        80
+
+#define WHITE_ON_BLACK  0x0f
+
+#define REG_SCREEN_CTRL 0x3d4
+#define REG_SCREEN_DATA 0x3d5
+
+void print_char(char c, int col, int row, char attr_byte);
+int get_screen_offset(int col, int row);