kernel/arch/x86/tty.c

   1 #include <io.h>
   2 #include <tty.h>
   3 #include <stdint.h>
   4
   5 #define VGA_WIDTH 80
   6 #define VGA_HEIGHT 25
   7
   8 static int cursor_x = 0; /* keep track of where cursor is */
   9 static int cursor_y = 0;
  10 static uint16_t crtc_port;
  11
  12 static inline uint8_t vga_get_color(const enum vga_color fg, const enum vga_color bg)
  13 {
  14         return fg&0xf | bg<<4;
  15 }
  16
  17 static inline uint16_t vga_get_char(const enum vga_color fg, const enum vga_color bg, char character)
  18 {
  19         return character | vga_get_color(fg, bg)<<8;
  20 }
  21
  22 static inline char *vga_get_memory_address(int x, int y)
  23 {
  24         return (char *) 0xb8000 + (y*VGA_WIDTH + x)*2;
  25 }
  26
  27 static void vga_scroll_up(void)
  28 {
  29         for (int y=1; y<VGA_HEIGHT; y++) {
  30                 for (int x = 0; x<VGA_WIDTH; x++) {
  31                         *vga_get_memory_address(x, y-1) = *vga_get_memory_address(x, y);
  32                 }
  33         }
  34
  35         for (int x = 0; x<VGA_WIDTH; x++) {
  36                 *vga_get_memory_address(x, VGA_HEIGHT-1) = vga_get_char(VGA_LIGHT_GRAY, VGA_BLACK, ' ');
  37         }
  38         cursor_y = VGA_HEIGHT - 1;
  39 }
  40
  41 static void vga_set_cursor(int x, int y)
  42 {
  43         uint16_t cursor_address = y*VGA_WIDTH + x;
  44
  45         outb(crtc_port, 0xe);
  46         outb(crtc_port+1, cursor_address>>8);
  47         outb(crtc_port, 0xf);
  48         outb(crtc_port+1, cursor_address);
  49 }
  50
  51 static void vga_screen_clear(void)
  52 {
  53         for (int y=0; y<VGA_HEIGHT; y++) {
  54                 for (int x=0; x<VGA_WIDTH; x++) {
  55                         *vga_get_memory_address(x, y) = vga_get_char(VGA_LIGHT_GRAY, VGA_BLACK, ' ');
  56                 }
  57         }
  58
  59         cursor_x = 0;
  60         cursor_y = 0;
  61         vga_set_cursor(0, 0);
  62 }
  63
  64 void vga_print_char(const char character, const enum vga_color fg, const enum vga_color bg)
  65 {
  66         if (character == '\n') {
  67                 cursor_x = 0;
  68                 cursor_y++;
  69         } else {
  70                 *vga_get_memory_address(cursor_x, cursor_y) = vga_get_char(fg, bg, character);
  71                 cursor_x++;
  72         }
  73
  74         if (cursor_x >= VGA_WIDTH) {
  75                 cursor_x = 0;
  76                 cursor_y++;
  77         }
  78
  79         if (cursor_y >= VGA_HEIGHT)
  80                 vga_scroll_up();
  81
  82         vga_set_cursor(cursor_x, cursor_y);
  83 }
  84
  85 void vga_initialize()
  86 {
  87         uint8_t vga_misc = inb(0x3cc);
  88         if (vga_misc&1)
  89                 crtc_port = 0x3d4;
  90         else
  91                 crtc_port = 0x3b4;
  92
  93         vga_screen_clear();
  94 }